FCC ID: CASTEL0048 One way paging transmitters T856-26-1010 & T856-26

 

M850-00 T856/857 General Information C1.3 Copyright TEL The photograph in Figure 1.1 on the next page will help you to identify the main circuit blocks in the T856. There is a similar photograph in Figure 4.4 which shows the main tuning and adjustment controls. Extending both these fold-outs will allow you to refer to both photographs while using the manual. The photograph in Figure 1.2 on the next page shows the T856 front panel con-

trols. 31/09/98 C1.4 T856/857 General Information M850-00 1 A B 0 1 n i Carrier Switch Keys the transmitter (while disabling the 600W line and microphone audio). 6 9 C 8 7 C D

n i o i d u a

. l c n i

) 1 e g n a r

D

r o t c e n n o c e g n a r

D

) F t r a P n i 2

. 2 n o i t c e S o t r e f e r

r e l l o r t n o c o r c i m

) d e t t i f f i

e g n a r

D a r t x e o t g n i l b a c r o f t c u d S S C T C d n a r e l l o r t n o c o r c i m t u p t u o F R e g n a r

D 5 891 0 AB C r e i f i l p m a e v i r d r e t i c x e r o s s e c o r p o i d u a r e t l i f s s a p w o l A P r e s i s e h t n y s s r o t a l u g e r O C V 2 3 4 On LED The On LED is lit when the T856 is transmitting. Line Sensitivity Sets the gain of the 600W line input of the audio processor. Supply LED The Supply LED is lit when DC power is supplied to the transmitter. Microphone Socket For connecting a T800-80 micro-

phone to allow local control of the transmitter. The 600W line is disabled when the PTT button is pressed. 1234567

y e K Figure 1.1 T856 Main Circuit Block Identification Figure 1.2 T856 Front Panel Controls 31/09/98 Copyright TEL M850-00 T856/857 General Information C1.5 Copyright TEL The photograph in Figure 1.3 on the next page will help you to identify the main circuit blocks in the T857. There is a similar photograph in Figure 4.5 which shows the main tuning and adjustment controls. Extending both these fold-outs will allow you to refer to both photographs while using the manual. The photograph in Figure 1.4 on the next page shows the T857 front panel con-

trols. 31/09/98 C1.6 T856/857 General Information M850-00 1 A 9 B n i Carrier Switch Keys the exciter (while disabling the 600W line and microphone audio). 5 8 C 7 6

) d e t t i f f i

e g n a r

D a r t x e o t g n i l b a c r o f t c u d e g n a r

D C D

n i o i d u a

. l c n i

) 1 e g n a r

D

r o t c e n n o c e g n a r

D t u p t u o F R

) F t r a P n i 2

. 2 n o i t c e S o t r e f e r

r e l l o r t n o c o r c i m 2 3 4 89 AB C r e i f i l p m a e v i r d r e t i c x e r o s s e c o r p o i d u a r e t l i f s s a p w o l r e s i s e h t n y s s r o t a l u g e r O C V S S C T C d n a r e l l o r t n o c o r c i m On LED The On LED is lit when the T857 is transmitting. Line Sensitivity Sets the gain of the 600W line input of the audio processor. Supply LED The Supply LED is lit when DC power is supplied to the exciter. Microphone Socket For connecting a T800-80 micro-

phone to allow local control of the exciter. The 600W line is dis-

abled when the PTT button is pressed. 1234567

y e K Figure 1.3 T857 Main Circuit Block Identification Figure 1.4 T857 Front Panel Controls 31/09/98 Copyright TEL M850-00 T856/857 Functional Testing C4.9 RV805 CTCSS level adjust SK805

=IC700 TCXO

#CV475 L1 R481 L481 C6 RV330 shutdown power level IC350 pin 3 RV320 shutdown temperature RV310 power control SW230 carrier RV210 line sensitivity RV220 compression level PL205 PL220 PL215 PL210 Figure 4.4 T856 Main Tuning & Adjustment Controls 31/09/98 The photograph printed at right will help you to identify the main controls used in tuning and adjust-

ing the T856. There is a similar photograph in Figure 1.1 which shows the main circuit blocks. Extending both these fold-outs will allow you to refer to both photo-

graphs while using the manual. Copyright TEL C4.10 T856/857 Functional Testing M850-00 31/09/98 Copyright TEL M850-00 T856/857 Functional Testing C4.11 RV805 CTCSS level adjust SK805

=IC700 TCXO L1 C6 The photograph printed at right will help you to identify the main controls used in tuning and adjust-

ing the T857. There is a similar photograph in Figure 1.3 which shows the main circuit blocks. Extending both these fold-outs will allow you to refer to both photo-

graphs while using the manual. Copyright TEL SW230 carrier RV210 line sensitivity RV220 compression level PL205 PL220 PL215 PL210 Figure 4.5 T857 Main Tuning & Adjustment Controls 31/09/98

 

 

M850-00 2 2.1 T856/857 Installation Rack Mounting The T856 transmitter and T857 exciter are designed for use in a standard 483mm rack frame using a Tait T800 Series II guide. The guide is securely mounted to the rack frame with front and rear retaining screws, and the T856/857 is secured into the guide with two front panel mounting screws. Figure 2.1 shows a standard, double module guide which can also be fitted with an optional backplane PCB to locate and mate the rear D-range connector(s). For more information on available guide kits, refer to the T800 Ancillary Equipment Service Manual or your nearest Tait Dealer or Customer Service Organisation. A rear mounted N-type connector is used for RF output on the T856/857, while all DC, audio and control connections are via the rear mounted D-range connector, D-range 1

(PL100). An additional rear D-range connector (T800-03-0000) can be fitted when remote multichannel operation, or additional control or low frequency lines are required (refer to Figure 2.2). Rack Mounting Holes

Figure 2.1 T800-41-0002 Double Guide Kit Front Panel Mounting Holes Rack Mounting Holes Aperture For RF Connectors Slots For D-Range Connectors Rack Mounting Holes

Figure 2.2 T856/857 Chassis Connectors N-Type Connector D-Range Plug

(D-Range 1) Rack Mounting Holes Optional Backplane PCB Mounts On Rear Of Guide Front Panel Mounting Hole Space For Optional D-Range Plug

(D-Range 2) Copyright TEL T856/857 Installation F2.1 2.2 Rack Wiring The D-range input and output connections are shown in Figure 2.3 and Figure 2.4. Ensure that the cables are not subjected to any stresses due to tight bends or incorrect lengths. Make sure the RF coax cable to the N-type connector is free from sharp bends or twists. If access to the rear of the rack frame is restricted, the cable should be long enough to allow the chassis to be fully withdrawn from the guide. 10.8 to 16V DC High isolation keying option:

6 to 50V DC To key transmitter:

high impedance

<0.7V = key Power supply, -ve earth

+13.8V Opto Key +

Opto Key -

Tx Key Gnd 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 Line I/P1 Line I/P2 Line I/P3 Line I/P4 Tx Enable Audio 2 Serial Com CTCSS Sensitivity: -30dBm Short together for normal operation To key PA, open collector External/auxiliary audio processing Can be configured as Can be configured as Audio 1 by internal link Audio 1 by internal resistors if required. link resistors if required Refer to Part I. External CTCSS input:

1kHz deviation @150Hz (500mV rms) Figure 2.3 T856/857 D-Range 1 Wiring - Rear View TX RELAY DRV CTCSS DISABLE CH_SLCT 7 SERIAL COM AUX-OUT 0 AUX-OUT 1 AUX-OUT 2 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 CH_SLCT 0 CH_SLCT 1 CH_SLCT 2 CH_SLCT 3 CH_SLCT 4 CH_SLCT 5 CH_SLCT 6 GND Open drain type;

capable of sinking 2.25mA via 2k2W

V max. = 5V ds Figure 2.4 T856/857 D-Range 2 Wiring - Rear View

(standard T800-03-0000 kit) Note:

Figure 2.4 above shows the standard pin allocations for the T800-03-0000 auxiliary D-range kit. A T800-03 auxiliary D-range kit is also available for special applications requiring custom internal wiring. 31/09/98 F2.2 2.3 T856/857 Installation Power Supply M850-00 If a power supply other than an appropriate Tait model is used, ensure that it is capable of providing enough current to drive the T800 system and is also free from excessive ripple or noise. The system should be protected by the use of appropriately rated fuses in the power supply. Note:

It is particularly important when the prime power source is a battery that fuses be employed in all supply lines. 2.4 Reverse Polarity & Overvoltage Protection A crowbar diode is fitted to all T856 transmitters and T857 exciters for protection against connection to a power supply of incorrect polarity. It also provides overvoltage protection from voltage transients caused by lightning strikes. Note:

A fuse must be fitted in the power supply line for the diode to provide effec-

tive protection. 29/02/00 Copyright TEL M850-00 3 3.1 Caution:

T858/859 Installation Rack Mounting If you require continuous operation of the T858, leave the rack module position immediately adjacent to the finned heatsink empty. There should be adequate airflow over the fins at all times. Extra airflow can be provided by fitting an auxiliary fan kit such as the T800-19-0010

(refer to the T800 Ancillary Equipment Service Manual or your nearest Tait Dealer or Customer Service Organisation for more details). The T858 and T859 PAs are designed for use in a standard 483mm rack frame using Tait T800 Series II guide rails. The guide rails are securely mounted to the rack frame with front and rear retaining screws, and the PA is secured into the guide with two (T858) or four

(T859) front panel mounting screws. Figure 3.1 shows the standard, double width guide designed for use with the T859, while Figure 3.3 shows how the PA can be latched in the extended posi-

tion. For more information on availa-

ble guide kits, refer to the T800 Ancillary Equipment Service Manual or your nearest Tait Dealer or Customer Service Organisation. Rack Mounting Holes Front Panel Mounting Holes Rack Mounting Holes Rack Mounting Holes Figure 3.1 T800-45-0001 PA Guide Kit The PA rear panel has three connectors: a BNC for RF input (from an adjacent T857 exciter), an N-type for RF output and a D-range for all DC, audio and control connec-

tions (refer to Figure 3.2). T858 T859 Copyright TEL N-Type Connector BNC Connector D-Range Connector N-Type Connector BNC Connector D-Range Connector Figure 3.2 T858/859 Chassis Connectors T858/859 Installation F3.1 Top Rail RF Output RF Input D-range Bottom Rail Figure 3.3 T858/859 PA In Latched Position Note:

You will need appropriate extension leads if you wish to carry out any adjustment procedures with the PA withdrawn from the rack in the latched position. Alternatively, disconnect and withdraw the PA and reconnect it behind the rack. 3.2 Rack Wiring The D-range input and output connections are shown in Figure 3.4. Ensure that the cables are not subjected to any stresses due to tight bends or incorrect lengths. Make sure the RF coax cables to the N-type and BNC connectors are free from sharp bends or twists. If access to the rear of the rack frame is restricted, the cables should be long enough to allow the chassis to be fully withdrawn from the guide. 10.8 to 16V DC

+13.8V Pull low to enable alarm outputs Tx Key Gnd Power supply, -ve earth 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 Normally low, float on alarm conditions. 500mA sink capability. Forward Power Alarm Reverse Power Alarm Forward Power Metering Reverse Power Metering Will drive a coil meter Figure 3.4 T858/859 D-Range Wiring - Rear View 31/01/99 F3.2 3.3 T858/859 Installation Power Supply M850-00 If a power supply other than an appropriate Tait model is used, ensure that it is capable of providing enough current to drive the T800 system and is also free from excessive ripple or noise. The system should be protected by the use of appropriately rated fuses in the power supply. Note:

It is particularly important when the prime power source is a battery that fuses be employed in all supply lines. Caution:

Connect the power supply directly to the PA, and not via connector blocks. This will avoid overheating of connector blocks that are not of the correct current rating. 3.4 Reverse Polarity & Overvoltage Protection A crowbar diode is fitted to all T858/859 PAs for protection against connection to a power supply of incorrect polarity. It also provides overvoltage protection from voltage transients caused by lightning strikes. Note:

A fuse must be fitted in the power supply line for the diode to provide effec-

tive protection. 29/02/00 Copyright TEL

 

 

M850-00 CI Part C T856 Transmitter & T857 Exciter This part of the manual is divided into six sections, as listed below. There is a detailed table of contents at the start of each section. Section Title 1 2 3 4 5 6 General Information Circuit Operation Initial Tuning & Adjustment Functional Testing Fault Finding PCB Information Copyright TEL 31/09/98 CII M850-00 31/09/98 Copyright TEL M850-00 1 T856/857 General Information C1.1 T856/857 General Information This section provides a brief description of the T856 transmitter and T857 exciter, along with detailed specifications and a list of types available. The following topics are covered in this section. Title Page Section 1.1 1.2 1.2.1 1.2.2 1.2.3 1.2.4 1.2.4.1 1.2.4.2 1.2.4.3 1.2.5 1.2.6 1.2.6.1 1.2.6.2 1.2.6.3 Introduction Specifications Introduction General RF Section Audio Processor Inputs Modulation Characteristics CTCSS Microcontroller Test Standards European Telecommunication Standard DTI CEPT Recommendation T/R-24-01 Telecommunications Industry Association 1.3 1.4 1.5 Product Codes T856 Standard Product Range T857 Standard Product Range Figure Title 1.1 1.2 1.3 1.4 T856 Main Circuit Block Identification T856 Front Panel Controls T857 Main Circuit Block Identification T857 Front Panel Controls 1.7 1.8 1.8 1.8 1.9 1.10 1.10 1.11 1.11 1.11 1.12 1.12 1.12 1.12 1.13 1.14 1.15 Page 1.4 1.4 1.6 1.6 Copyright TEL 31/09/98 C1.2 T856/857 General Information M850-00 31/09/98 Copyright TEL M850-00 T856/857 General Information C1.3 replace A4 pages C1.3/C1.4 with A3 pages C1.3/C1.4 Copyright TEL 31/09/98 C1.4 T856/857 General Information M850-00 replace A4 pages C1.3/C1.4 with A3 pages C1.3/C1.4 31/09/98 Copyright TEL M850-00 T856/857 General Information C1.5 replace A4 pages C1.5/C1.6 with A3 pages C1.5/C1.6 Copyright TEL 31/09/98 C1.6 T856/857 General Information M850-00 replace A4 pages C1.5/C1.6 with A3 pages C1.5/C1.6 31/09/98 Copyright TEL M850-00 T856/857 General Information C1.7 1.1 Introduction The T856 is a synthesised, microprocessor controlled FM base station transmitter designed for single or multichannel operation in the 400 to 520MHz frequency range1 with a standard power output of 25W. The RF section of the transmitter comprises a fre-

quency synthesiser which provides 100mW of frequency modulated RF drive to a two stage, wide band output driver followed by a 25W power amplifier. A thermal shut-

down feature is provided in the T856 in case operating temperatures exceed acceptable levels. The T857 is a synthesised, microprocessor controlled FM base station exciter designed for single or multichannel operation in the 400 to 520MHz frequency range1. With a standard power output of only 1W, the exciter is designed for use with the T858 50W or T859 100W power amplifiers. The RF section of the exciter comprises a frequency syn-

thesiser which provides 100mW of frequency modulated RF drive to a two stage, wide band output amplifier. A wide selection of audio characteristics may be obtained from the audio processor. Optional circuit blocks are an audio compressor and a pre-emphasis stage. They can be bypassed or linked to one or both audio inputs, and then back into the remaining audio circuitry in almost any combination. All audio processor options are link selectable. The synthesiser frequency is programmed via the serial communications port. Eight channel select lines are accessible via an optional D-range connector (D-range 2 -

T800-03-0000) at the rear of the set. All components except those of the VCO are mounted on a single PCB. This is secured to a die-cast chassis which is divided into compartments to individually shield each sec-

tion of circuitry. Access to both sides of the main circuit board is obtained by removing each of the chassis lids. There is provision within the chassis to mount small option PCBs. The front panel controls include line sensitivity, microphone socket and carrier switch. This switch turns on the carrier (unmodulated) as an aid to servicing. The T856 and T857 are both 60mm wide and each occupies a single space in a Tait rack frame, which has the ability to accommodate up to seven standard modules. 1. Although capable of operating over the 400-520MHz frequency range, the T856 and T857 have an 8MHz switching range (see Section 1.2.3 and Section 3.1). Copyright TEL 31/09/98 C1.8 1.2 T856/857 General Information M850-00 Specifications 1.2.1 Introduction The performance figures given are minimum figures, unless otherwise indicated, for equipment tuned with the maximum switching range and operating at standard room temperature (+22 C to +28 C) and standard test voltage (13.8V DC). Where applicable, the test methods used to obtain the following performance figures are those described in the EIA and ETS specifications. However, there are several parameters for which performance according to the CEPT specification is given. Refer to Section 1.2.6 for details of test standards. Details of test methods and the conditions which apply for Type Approval testing in all countries can be obtained from Tait Electronics Ltd. The terms "wide bandwidth", "mid bandwidth" and "narrow bandwidth" used in this and following sections are defined in the following table. Channel Spacing Modulation 100% Deviation Receiver IF Bandwidth Wide Bandwidth Mid Bandwidth Narrow Bandwidth 25kHz 20kHz 12.5kHz 5.0kHz 4.0kHz 2.5kHz 15.0kHz 12.0kHz 7.5kHz 1.2.2 General Number Of Channels Supply Voltage:

.. 128 (standard)1 Operating Voltage Standard Test Voltage Polarity Polarity Protection Line Keying Supply (if required)

.. 10.8 to 16V DC

.. 13.8V DC

.. negative earth only

.. crowbar diode

-50V DC Supply Current:

Transmit Standby

- T856

- T857

- T856

- T857 Operating Temperature Range

.. 5.5A (typical)

.. 750mA

.. 165mA (typical)

.. 150mA (typical)

-20 C to +60 C 1. Additional channels may be factory programmed. Contact your nearest Tait Dealer or Customer Service Organisation. 29/02/00 Copyright TEL M850-00 Dimensions:

Height Width Length Weight T856/857 General Information C1.9

.. 183mm

.. 60mm

.. 322mm

.. 2.1kg Time-Out Timer (optional) Tail Timer

.. 0 to 5 minutes1 adjustable in 10 sec-

ond steps

.. 0 to 5 seconds adjustable in 100ms2 steps Transmit Key Time

.. <30ms Transmit Lockout Timer

.. 0 to 1 minute adjustable in 10 second steps 1.2.3 RF Section Frequency Range Modulation Type Frequency Increment Switching Range

.. 400-520MHz (refer to Section 1.4 and Section 1.5)

.. FM

.. 5 or 6.25kHz

.. 8MHz (i.e. 4MHz from the centre frequency) Load Impedance

.. 50 ohms Frequency Stability

(see also Section 1.4 and Section 1.5) Adjacent Channel Power (full deviation):

.. 1ppm, -20 C to +60 C Wide Bandwidth (WB)

(25kHz/15kHz B/W) Mid Bandwidth (MB)

(20kHz/12kHz B/W) Narrow Bandwidth (NB)

(12.5kHz/7.5kHz B/W)

-75dBc

-70dBc

-65dBc Transmitter Switching

.. complies with ETS 300 113 1. Adjustable from 0 to 10 minutes in PGM800Win version 2.12 and later. 2. Adjustable in 20ms steps in PGM800Win version 2.12 and later. Copyright TEL 29/02/00 C1.10 T856/857 General Information M850-00 Transmitter Side Band Noise:

(no modulation, 15kHz bandwidth) At 25kHz At 1MHz Intermodulation T856 Mismatch Capability:

Ruggedness Stability Radiated Spurious Emissions:

Transmit Standby Conducted Spurious Emissions: (T856 Only) Transmit Standby Power Output:

T856 T857

- Rated Power

- Range Of Adjustment Duty Cycle (T856 Only) 1.2.4 Audio Processor 1.2.4.1 Inputs Inputs Available Line Input:

-95dBc

-105dBc

-40dBc with interfering signal of

-30dBc

-70dBc with 25dB isolation

& interfering signal of -30dBc

(PA with output isolator) refer to your nearest Tait Dealer or Customer Service Organisation

.. 3:1 VSWR (all phase angles)

-36dBm to 1GHz

-30dBm 1GHz to 4GHz

-57dBm to 1GHz

-47dBm 1GHz to 4GHz

-36dBm to 1GHz

-30dBm 1GHz to 4GHz

-57dBm to 1GHz

-47dBm 1GHz to 4GHz

.. 25W (see Duty Cycle)

.. 5-25W

.. 1W 300mW

.. 100% @ 25W at +25 C

.. 25% @ 25W at +60 C

.. 100% @ 10W at +40 C

.. line, microphone and CTCSS Impedance Sensitivity (60% modulation @ 1kHz)-

With Compressor Without Compressor

.. 600 ohms (balanced)

-50dBm

-30dBm 29/02/00 Copyright TEL M850-00 Microphone Input:

T856/857 General Information C1.11 Impedance Sensitivity (60% modulation @ 1kHz)-

With Compressor Without Compressor

.. 600 ohms

-70dBm

-50dBm 1.2.4.2 Modulation Characteristics Frequency Response

(below limiting) Line And Microphone Inputs:

Pre-emphasised Response-

Bandwidth Below Limiting Flat Response Above Limiting Response Distortion Hum And Noise:

Wide Bandwidth Mid Bandwidth Narrow Bandwidth Compressor (optional):

Attack Time Decay Time Range 1.2.4.3 CTCSS Standard Tones Frequency Error

(from EIA tones)

.. flat or pre-emphasised (optional)

.. 300Hz to 3kHz (WB & MB)

.. 300Hz to 2.55kHz (NB)

.. within +1, -3dB of a 6dB/octave pre-emphasis characteristic

.. within +1, -2dB of output at 1kHz

.. within +1, -2dB of a flat response

(ref. 1kHz)

.. 2% max. . . .

-55dB (300Hz to 3kHz [EIA]) typical

-54dB (CEPT)

-50dB (CEPT)

.. 10ms

.. 800ms

.. 50dB

.. all 37 EIA group A, B and C tones plus 13 commonly used tones

.. 0.08% max. Generated Tone Distortion

.. 1.2% max. Generated Tone Flatness

.. flat across 67 to 250.3Hz to within 1dB Modulation Level Modulated Distortion

.. adjustable

.. <5%

Copyright TEL 29/02/00 C1.12 T856/857 General Information M850-00 1.2.5 Microcontroller Auxiliary Ports:

Open Drain Type Vds max. 1.2.6 Test Standards

.. capable of sinking 2.25mA via 2k2W

.. 5V Where applicable, this equipment is tested in accordance with the following standards. 1.2.6.1 European Telecommunication Standard ETS 300 086 January 1991 Radio equipment and systems; land mobile service; technical characteristics and test conditions for radio equipment with an internal or external RF connector intended pri-

marily for analogue speech. ETS 300 113 March 1996 Radio equipment and systems; land mobile service; technical characteristics and test conditions for radio equipment intended for the transmission of data (and speech) and having an antenna connector. ETS 300 219 October 1993 Radio equipment and systems; land mobile service; technical characteristics and test conditions for radio equipment transmitting signals to initiate a specific response in the receiver. ETS 300 279 February 1996 Radio equipment and systems; electromagnetic compatibility (EMC) standard for pri-

vate land mobile radio (PMR) and ancillary equipment (speech and/or non-speech). 1.2.6.2 DTI CEPT Recommendation T/R-24-01 Annex I: 1988 Technical characteristics and test conditions for radio equipment in the land mobile service intended primarily for analogue speech. Annex II: 1988 Technical characteristics of radio equipment in the land mobile service with regard to quality and stability of transmission. 1.2.6.3 Telecommunications Industry Association ANSI/TIA/EIA-603-1992 Land mobile FM or PM communications equipment measurement and performance standards. 29/02/00 Copyright TEL M850-00 T856/857 General Information C1.13 1.3 Product Codes The three groups of digits in the T850 Series II product code provide information about the model, type and options fitted, according to the conventions described below. The following explanation of T850 Series II product codes is not intended to suggest that any combination of features is necessarily available in any one product. Consult your nearest Tait Dealer or Customer Service Organisation for more information regarding the availability of specific models, types and options. Model The Model group indicates the basic function of the product, as follows:

T85X-XX-XXXX T855 receiver T856 25W transmitter T857 exciter T858 50W power amplifier T859 100W power amplifier Type The Type group uses two digits to indicate the basic RF configuration of the product. The first digit in the Type group designates the frequency range:

T85X-XX-XXXX 1 for 400-440MHz 2 for 440-480MHz 3 for 480-520MHz The second digit in the Type group indicates the channel spacing:

T85X-XX-XXXX 0 for wide bandwidth (25kHz) 3 for mid bandwidth (20kHz) 5 for narrow bandwidth (12.5kHz) 6 for United States market only Options T85X-XX-XXXX The Options group uses four digits and/or letters to indicate any options that may be fitted to the product. This includes standard options and special options for specific customers. 0000 indicates a standard Tait product with no options fitted. The large number of options precludes listing them here. Copyright TEL 29/02/00 C1.14 T856/857 General Information M850-00 1.4 T856 Standard Product Range The following table lists the range of standard T856 types (i.e. no options fitted) availa-

ble at the time this manual was published. Consult your nearest Tait Dealer or Cus-

tomer Service Organisation for more information. Frequency Range (MHz) Deviation (kHz) TCXO 1ppm -20C to +60C 400-440 2.5 2.5 4 5 Transmitter Type: T856-

16-0000a 15-0000 13-0000 10-0000 Frequency Range (MHz) Deviation (kHz) TCXO 1ppm -20C to +60C 440-480 2.5 2.5 4 5 Transmitter Type: T856-

26-0000a 25-0000 23-0000 20-0000 Frequency Range (MHz) Deviation TXCO 1ppm -20 to +60C 480-520 2.5 2.5 5 Transmitter Type: T856-

36-0000a 35-0000 30-0000 a. United States market only. Caution:

T856-1X-XXXX Product Types The 406 to 406.1MHz frequency range is reserved worldwide for use by Distress Beacons. Do not program transmitters to operate in this fre-

quency range. You can identify the transmitter type by checking the product code printed on a label on the rear of the chassis (Figure 1.1 in Part A shows typical labels). You can further verify the transmitter type by checking the placement of an SMD resistor in the table that is screen printed onto the PCB (refer to Section 6.1 for more details). 29/02/00 Copyright TEL M850-00 T856/857 General Information C1.15 1.5 T857 Standard Product Range The following table lists the range of standard T857 types (i.e. no options fitted and cyclic keying disabled) available at the time this manual was published. Consult your nearest Tait Dealer or Customer Service Organisation for more information. Frequency Range (MHz) Deviation (kHz) TCXO 1ppm -20C to +60C 400-440 2.5 4 5 2.5 Exciter Type: T857-

16-0000a 15-0000 13-0000 10-0000 Frequency Range (MHz) Deviation (kHz) TCXO 1ppm -20C to +60C 440-480 2.5 4 5 2.5 Exciter Type: T857-

26-0000a 25-0000 23-0000 20-0000 Frequency Range (MHz) Deviation TXCO 1ppm -20 to +60C 480-520 2.5 2.5 5 Exciter Type: T857-

36-0000a 35-0000 30-0000 a. United States market only. Caution:

T857-1X-XXXX Product Types The 406 to 406.1MHz frequency range is reserved worldwide for use by Distress Beacons. Do not program exciters to operate in this frequency range. You can identify the exciter type by checking the product code printed on a label on the rear of the chassis (Figure 1.1 in Part A shows typical labels). You can further verify the exciter type by checking the placement of an SMD resistor in the table that is screen printed onto the PCB (refer to Section 6.1 for more details). Copyright TEL 29/02/00 C1.16 T856/857 General Information M850-00 31/09/98 Copyright TEL M850-00 2 T856/857 Circuit Operation C2.1 T856/857 Circuit Operation This section provides a basic description of the circuit operation of the T856 transmitter and T857 exciter. Note:

Unless otherwise specified, the term "PGM800Win" used in this and follow-

ing sections refers to version 2.00 and later of the software. Refer to Section 6 where the parts lists, grid reference index and diagrams will provide detailed information on identifying and locating components and test points on the main PCB. The parts list and diagrams for the VCO PCB are in Part E. The following topics are covered in this section. Section Title Page 2.3.1 2.4.1 2.5.1 2.5.2 2.5.3 2.5.4 2.5.5 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Introduction Microcontroller Synthesised Local Oscillator Two Point Modulation VCO VCO Supply Audio Processor General Audio Inputs Keying Inputs Compressor (Automatic Level Control (ALC)) Outputs To Modulators Power Supply & Regulator Circuits Transmit Timers T856 Drive Amplifier & PA T857 Exciter Drive Amplifier 2.3 2.4 2.5 2.6 2.7 2.7 2.8 2.8 2.8 2.9 2.9 2.9 2.10 2.11 2.12 2.13 Copyright TEL 31/09/98 C2.2 T856/857 Circuit Operation Figure Title 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 T856 High Level Block Diagram T857 High Level Block Diagram T856/857 Microcontroller Block Diagram T856/857 Synthesiser Block Diagram T856/857 Two Point Modulation T856/857 Audio Processor Block Diagram T856/857 Power Supply & Regulators Block Diagram T856/857 Transmit Timers M850-00 Page 2.3 2.3 2.4 2.5 2.6 2.8 2.10 2.11 31/09/98 Copyright TEL M850-00 T856/857 Circuit Operation C2.3 2.1 Introduction The individual circuit blocks which make up the T856 and T857 are:

synthesiser VCO audio processor drive amplifier power amplifier (T856 only) voltage regulators. Each of these circuit blocks is set in its own shielded compartment, formed as an inte-

gral part of the main chassis. The configuration of the circuit blocks may be seen on a functional level in Figure 2.1 and Figure 2.2. Refer to the circuit diagrams in Section 6.2 (T856) or 6.3 (T857) for more detail. Reference Oscillator 12.8MHz Microphone Synthesiser

+22dBm Lock Detect Audio Processor PIN Switch Drive Amp. Exciter Output

(+30dBm to

+33dBm) PA Directional Coupler Low Pass Filter Transmitter Output

(25W) Power Control Line Transformer Time Delay Time Delay

Gate Ramp Gen. Time Delay VCO Tx Reg Reference Oscillator 12.8MHz Microphone Line Transformer Figure 2.1 T856 High Level Block Diagram PIN Switch Drive Amp. Low Pass Filter Synthesiser

+22dBm Audio Processor Lock Detect

Gate Switching Control Time Delay Ramp Gen. Exciter Output

(+28dBm to

+31dBm) PA Control Signal

(via exciter RF coax) Tx Reg Time Delay VCO Figure 2.2 T857 High Level Block Diagram Copyright TEL 31/09/98 C2.4 2.2 T856/857 Circuit Operation Microcontroller M850-00

(Refer to the microcontroller circuit diagram (sheet 8) in Section 6.2 or 6.3.) 5V Digital Regulator 5V Watchdog Reset Reset Microcontroller Cavity Channel Select Port Auxiliary Output Port Dual Digital Potentiometer Microcontroller Converter CTCSS Encoder EEPROM Synthesiser 12.8MHz Clock External Serial Port CTCSS Tone Figure 2.3 T856/857 Microcontroller Block Diagram Overall system control of the T856/857 is accomplished by the use of a member of the 80C51 family of microcontrollers (IC810). It runs from internal ROM and RAM, thus leaving all four ports free for input/output functions. Non-volatile data storage is achieved by serial communication with a 16kBit EEPROM

(IC820). This serial bus is also used by the microcontroller to program the synthesiser

(IC740) and deviation control EPOTS (IC220). The main tasks of the microcontroller are as follows:

program the synthesiser and EPOT;

interface with the PGM800Win programming software at 9600 baud via the serial communication lines on D-range 1 (PL100) & D-range 2;

monitor channel change inputs from D-range 2;

generate timing waveforms for CTCSS encoding;

coordinate and implement timing control of the exciter/transmitter. control the front panel "Supply" LED (refer to Section 5.3). 29/02/00 Copyright TEL M850-00 T856/857 Circuit Operation C2.5 2.3 Synthesised Local Oscillator

(Refer to the synthesiser circuit diagram (sheet 7) in Section 6.2 or 6.3 and the VCO cir-

cuit diagram in Part E.) Fixed Divider

/64 Phase Modulator 12.8MHz Reference Oscillator Ref Mod Serial Bus Clk Data En Controller FREQUENCY SYNTHESISER IC Reference Divider Phase Detector Charge Pump Loop Filter VCO Modulation VCO PCB Output Buffer VCO Buffer

/R fref

+22dBm L.O. Programmable Divider Prescaler

/N 64/65 fin Divider Buffer Figure 2.4 T856/857 Synthesiser Block Diagram The synthesiser (IC740) employs a phase-locked loop (PLL) to lock a voltage controlled oscillator (VCO) to a given reference frequency. The synthesiser receives the divider information from the control microprocessor via a 3 wire serial bus (clock, data, enable). When the data has been latched in, the synthesiser processes the incoming signals from the VCO buffer (fin) and the phase modulator (fref). A reference oscillator at 12.8MHz (=IC700) is buffered (IC710 pins 3 & 4) and divided down to 200kHz (IC730). This 200kHz square wave is then summed with the modulat-

ing audio and passed to an integrator (IC720 pins 9 & 8, Q710, Q720). This produces a ramping waveform which is centred around a DC level determined by the incoming audio. IC720 pins 5 & 6 perform as a comparator, ultimately producing a phase-modu-

lated 200kHz square wave. This is followed by another phase shifting stage (IC720 pins 3 & 4, Q730, Q740), before being divided down to 6.25kHz or 5kHz within the synthe-

siser IC (IC740). A buffered output of the VCO (Q795) is divided with a prescaler and programmable divider which is incorporated into the synthesiser chip (IC740). This signal is compared with the phase modulated reference signal at the phase detector (also part of the synthe-

siser chip). The phase detector outputs drive a balanced charge pump circuit (Q760, Q770, Q775, Q780, Q785) and active loop filter (IC750 pins 5, 6 & 7, Q790) which pro-

duces a DC voltage between 0V and 20V to tune the VCO. This VCO control line is fur-

ther filtered to attenuate noise and other spurious signals. Note that the VCO frequency increases with increasing control voltage. If the synthesiser loop loses lock, a pulsed signal appears at LD (pin 2) of IC740. This signal is filtered and buffered by IC750 pins 1, 2 & 3, producing the Lock-Detect signal used to shut off the power supply to the drive amplifier. IC750 pin 1 is at 20V when the synthesiser is out of lock. Copyright TEL 31/09/98 S C2.6 T856/857 Circuit Operation M850-00 2.3.1 Two Point Modulation Frequency modulation occurs by modulating both the VCO input and the synthesiser reference input. This process is called two point modulation and ensures a flat modula-

tion response from 67Hz to 3kHz (2.55kHz for narrow bandwidth). The PLL has a fast response time, allowing a Tx key-up time of <30ms. Because of this fast response time the PLL sees lower modulation frequencies superimposed on the VCO as an error and corrects for it, resulting in no modulation on the carrier. At modu-

lation frequencies greater than 300Hz the loop cannot correct fast enough and modula-

tion is seen on the carrier. The response of the loop to VCO modulation is shown by f2 in Figure 2.5 below. To achieve low frequency modulation, the reference oscillator is also modulated so that the phase detector of IC740 detects no frequency error under modulation. Thus, the synthesiser loop will not attempt to correct for modulation and the audio frequency response of the transmitter remains unaffected. The response of the loop to reference frequency modulation is shown by f1 in Figure 2.5. The reference modulation is controlled by a 256-step 10k electronic potentiometer

(EPOT) which is adjustable via PGM800Win. The EPOT is made up of 256 resistive sec-

tions (representing approximately 39W each) which can be individually addressed by the microcontroller. Each section can be switched in or out of circuit to achieve the required total resistance, thus giving control of the reference modulation. f 1 f 2 TCXO VCO Deviation Frequency Figure 2.5 T856/857 Two Point Modulation 29/02/00 Copyright TEL M850-00 2.4 VCO T856/857 Circuit Operation C2.7

(Refer to the VCO circuit diagram in Part E.) The VCO transistor (Q1) operates in a common emitter configuration, with an LC tank circuit coupled between its gate and drain to provide the feedback necessary for oscilla-

tion. The VCO control voltage from the loop filter (IC750) is applied to the varicaps

(D1-D2) to facilitate tuning within an 8MHz band of frequencies. A trimcap (C6) is used for coarse tuning of the VCO. The output from the oscillator circuit drives a cascode amplifier stage (Q2, Q3) which supplies +10dBm (typically) to a further stage of amplifi-

cation, Q5. This is the final amplifier on the VCO PCB, and delivers +20dBm (typically) to the exciter drive amplifier. A low level "sniff" is taken from the input to Q5 and used to drive the divider buffer for the synthesiser (IC740). The VCO operates at the actual output frequency of the exciter, i.e. there are no multi-

plier stages. It is modulated by superimposing the audio signal onto the control voltage and by phase modulating the reference signal. 2.4.1 VCO Supply The VCO is supplied from two switched +9V supplies under the control of the Tx-Reg. supply. The VCO and buffer amplifier are supplied from one +9V switched supply by Q540 via the C multiplier (Q550, C530 on the T856 and C550 on the T857). The output amplifier is supplied from the other +9V supply by Q520, Q530, and Q510. A delay circuit holds the VCO on for a short time after the Tx-Reg. supply has been switched off. This is to allow the RF power circuits (both exciter and PA) to ramp down in the correct manner before the VCO is switched off. Copyright TEL 31/09/98 C2.8 2.5 T856/857 Circuit Operation Audio Processor

(Refer to the audio processor circuit diagram (sheet 2) in Section 6.2 or 6.3.) Carrier

Opto-Key _ Tx Key PTT Microphone Input Line Input Opto-coupler Constant Current Sink Microphone Pre-amp. 3 5 Link B C PL205 Audio 1 Audio 2 Tx Enable 4 6 8 Link H I J PL215 3 5 7 Compressor 6 4 2 Link N M L PL210 5 3 1 Pre-

emphasis 3 1 Link E D PL220 4 2 4 6 Output Inhibit t u p t u O mic. s t u p n I line Multiplexer M850-00 Limiter Set Deviation Digital Pot. (EPOT) CTCSS Low Pass Filter Ref. Mod. Adjust Digital Pot. (EPOT) Buffer Integrator Output To VCO Ref. Mod. Figure 2.6 T856/857 Audio Processor Block Diagram 2.5.1 General The audio processor comprises several link selectable circuit blocks which may be con-

figured in a variety of combinations to suit individual requirements. The pre-emphasis network and compressor may be linked individually or cascaded between either or both audio inputs and the limiter. Refer to Section 3.5.1 for linking details. 2.5.2 Audio Inputs Two audio inputs are available: one from a 600 ohm balanced (or unbalanced) line, and the other from a local microphone. The microphone signal is passed first to a pre-ampli-

fier (Q210) and ultimately to a multiplexer (IC240), but in between may pass through the compressor (depending on the linking details). The line transformer is also con-

nected to the multiplexer and is disabled by the microphone PTT switch. A third input for external CTCSS tones is also provided. 29/02/00 Copyright TEL S M850-00 T856/857 Circuit Operation C2.9 2.5.3 Keying Inputs There are four ways to key the exciter:

pulling the Tx-Key line low (pin 13 on D-range 1 [PL100]) at the rear of the set);

pushing the "Carrier" button on the front panel - this will inhibit all audio;

using the PTT button on the local microphone, disabling audio from the line;

via the opto-key inputs (pins 11 and 12 on D-range 1 [PL100]) when electrical isolation is required. This features a constant current sink (Q270) to ensure reli-

able activation of the opto-coupler (IC250) at low keying voltages. 2.5.4 Compressor (Automatic Level Control (ALC)) The input signal is fed via a current controlled attenuator (Q230, Q220) to a high gain stage (IC230) from which the output signal is taken. This signal is passed to a compara-

tor (IC230) which toggles whenever the audio signal exceeds a DC threshold deter-

mined by RV220. Thus, the comparator produces a square wave whose mark-space ratio is determined by the amplitude of the audio signal. This square wave pumps up the reservoir capacitor (C233) which controls the attenuator (Q230, Q220), thus complet-

ing the feedback loop. The compression level is set by adjustment of the comparator threshold (RV220). Note:

Although the high dynamic range of the compressor allows the use of very low audio signal levels, such conditions will be accompanied by a degrada-

tion of the signal-to-noise ratio. Very low audio input levels should there-

fore be avoided where possible. 2.5.5 Outputs To Modulators The output signal from the limiter (IC210, IC230) is summed with a CTCSS tone at a summing amplifier (IC260). The signal is then low pass filtered (IC260) and split to sup-

ply the two modulators. Since the VCO modulator is a true frequency modulator, its audio is simply buffered

(IC260). The reference modulator, however, is a phase modulator and its audio must first be integrated (IC210). It is vital that the audio levels to the modulators are accurately set, relative to each other. Hence the inclusion of level adjustment in the reference modulator path. Once set, adjustments to absolute deviation may be made only by IC220, a 256-step 10k elec-

tronic potentiometer (EPOT), which is controlled via PGM800Win. The EPOT is made up of 256 resistive sections (representing approximately 39W each) which can be indi-

vidually addressed by the microcontroller. Each section can be switched in or out of cir-

cuit to achieve the required total resistance, thus adjusting the absolute deviation level. Copyright TEL 29/02/00 C2.10 T856/857 Circuit Operation M850-00 2.6 Power Supply & Regulator Circuits

(Refer to the regulators circuit diagram (sheet 6) in Section 6.2 or 6.3.) Buffer Tx Enable Micro-

controller

+9V Power Switch Tx Reg. 13.8V Nom. From Rear D-Range Crowbar Diode 5V Reg DC Amp Switching PS 5V Dig Reg LVI P Reset Watchdog Timer P 13.8V Nom. 5V 9V 20V 5V Dig Figure 2.7 T856/857 Power Supply & Regulators Block Diagram The T856 and T857 are designed to operate from a 10.8-16V DC supply (13.8V nominal). A 5.3V regulator (IC630) runs directly from the 13.8V rail, driving much of the synthe-

siser circuitry. It is also used as the reference for a DC amplifier (IC640, Q630, Q620) which provides a medium current capability 9V supply. The T856 has a regulator

(IC370) which produces 9V for use in the exciter and audio circuits. A switching power supply (Q660, Q670) runs from the 9V supply and provides a low current capability +20V supply. This is used to drive the synthesiser loop filter (IC750), giving a VCO control voltage range of up to 20V. Ultimate control of the transmitter is via the Tx-Reg. supply, switched from 9V by Q610. This is enabled via the Tx-Enable signal from the audio processor, and microprocessor. A crowbar diode is fitted for protection against connection to a power supply of incor-

rect polarity. It also provides transient overvoltage protection. Note:

A fuse must be fitted in the power supply line for the diode to provide effec-

tive protection. 29/02/00 Copyright TEL M850-00 T856/857 Circuit Operation C2.11 2.7 Transmit Timers The transmit tail timer, transmit timeout timer and transmit lockout timer can all be set from PGM800Win. The fields for setting these are found on the system information page. These three timers operate as follows (refer also to Figure 2.8):

Timer Transmit Tail Transmit Timeout Transmit Lockout Function Sets the tail time during which the transmitter stays keyed after the exter-

nal key source has been removed. Sets the maximum continuous trans-

mission time. Once the timer has timed out, the transmitter must be keyed again, unless prevented by the transmit lockout timer. Sets the period of time that must elapse after a timeout before the trans-

mitter can re-transmit. Once the timer has timed out, the transmitter can be keyed again. Adjustment 0-5 seconds in 100ms stepsa 0-300 secondsb in 10 second steps 0-60 seconds in 10 second steps a. Adjustable in 20ms steps in PGM800Win version 2.12 and later. b. Adjustable from 0 to 600 seconds in PGM800Win version 2.12 and later. Tx-Enable On Tx-Reg. Tail Time Tx-Enable On Tx-Reg. Lockout Time Timeout Time Figure 2.8 T856/857 Transmit Timers Copyright TEL 29/02/00 C2.12 T856/857 Circuit Operation M850-00 2.8 T856 Drive Amplifier & PA

(Refer to Figure 2.1 and the exciter and PA circuit diagrams (sheets 3 & 4) in Section 6.2.) The output power of the PA is maintained at a constant level via a power control loop applied to the two-stage, wide band exciter amplifier (Q350, Q355). The forward and reverse RF power levels are sensed via a dual directional coupler and detector diodes

(D440, D420 in the PA cavity). The detected DC signals are buffered (IC330 pins 3 & 5) and then summed with the power control level and fed to the control integrator (IC350 pin 6). The output control voltage is buffered by Q310 and Q315, and applied to the col-

lector of the wide band exciter amplifier. Note:

Forward and reflected power signals are summed so that, under high VSWR, the power control will turn the output RF level down. To reduce the spurious output level when the synthesiser is out-of-lock, the Tx-Reg. and Lock-Detect signals are gated to inhibit the PA control circuit and to switch off the RF signal at the input to the drive amplifier. This is achieved by a PIN switch attenuator

(D340, D380, D360). Cyclic keying control is provided by additional circuitry consisting of several time delay, ramp and gate stages:

Q325, IC350 Q355, Q325 Q335, Q340, Q345 power ramping Tx-Reg. and Lock-Detect gate delay and PIN switch drive. This is to allow the RF power circuits (both exciter and PA) to ramp up and down in a controlled manner so that minimal adjacent channel interference is generated during the transition. The output of the wide band amplifier is approximately 1W (+30dBm) for an input of 100mW (+20dBm) from the VCO, when the power control is set to maximum. A temperature sensor (R481) is provided so that the RF output power can be reduced to a preset level when a set temperature is exceeded. This is a protection circuit (IC350 pin 1, Q320) to prevent overheating, as the unit is not rated for continuous operation (refer to Section 1.2.3 for duty cycle specifications).

#R517, #R518 and #R519 form an attenuator to provide good VCO/exciter isolation as well as the correct exciter drive level. The attenuator (#R395, #R396 and #R397) aids in producing the correct exciter drive level to the PA over the three frequency ranges. The RF output from the exciter is fed to the driver stage (Q410) and then to the final

(Q420). DC is fed to the final via a low pass filter with special low frequency decou-

pling. CV475 tunes the output matching across the entire band. 31/09/98 Copyright TEL M850-00 T856/857 Circuit Operation C2.13 2.9 T857 Exciter Drive Amplifier

(Refer to Figure 2.2 and the exciter circuit diagram (sheet 3) in Section 6.3.) A two-stage, wide band amplifier (Q304, Q305) provides an output level of approxi-

mately 1W (+30dBm) for an input of 100mW (+20dBm) from the VCO. IC300 pin 1, Q302, and Q303 provide a 9V regulated supply for the exciter. To reduce the spurious output level when the synthesiser is out-of-lock, the Tx-Reg. and Lock-Detect signals are gated to inhibit the exciter control circuit and to switch off the RF signal at the input to the drive amplifier. This is achieved by a PIN switch attenuator

(D201, D202, D203). Cyclic keying control is provided by additional circuitry consisting of several time delay, ramp and gate stages:

Q301, Q302, Q303, IC300 Q310, Q311 Q306, Q307, Q308, Q309 power ramping Tx-Reg. and Lock-Detect gate delay and PIN switch drive. This is to allow the RF power circuits (both exciter and PA) to ramp up and down in a controlled manner so that minimal adjacent channel interference is generated during the transition. R517, R518 and R519 form a 3dB attenuator to provide good VCO/drive amplifier isola-

tion as well as the correct exciter drive level Note:

The exciter provides a DC control signal to the PA via the RF coax. This is injected via L314. Copyright TEL 29/02/00 C2.14 T856/857 Circuit Operation M850-00 31/09/98 Copyright TEL M850-00 3 Caution:

T856/857 Initial Tuning & Adjustment C3.1 T856/857 Initial Tuning & Adjustment This equipment contains CMOS devices which are susceptible to dam-

age from static charges. Refer to Section 1.2 in Part A for more infor-

mation on anti-static procedures when handling these devices. The following section describes both short and full tuning and adjustment procedures and provides information on:

channel programming selecting required audio links synthesiser alignment PA alignment (T856 only) modulator adjustment limiter adjustment setting line level compressor adjustment timer adjustment. Note:

Unless otherwise specified, the term "PGM800Win" used in this and follow-

ing sections refers to version 2.00 and later of the software. Refer to Figure 4.4 and Figure 4.5 which show the location of the main tuning and adjustment controls. Refer also to Section 6 where the parts lists, grid reference index and diagrams will provide detailed information on identifying and locating compo-

nents and test points on the main PCB. The parts list and diagrams for the VCO PCB are in Part E. Section Title Page 3.1 3.2 3.3 3.4 Introduction Channel Programming Test Equipment Required Short Tuning Procedure Introduction Synthesiser Alignment Output Power Adjustment (T856 Only) Two Point Modulation Adjustment CTCSS Encoder (If Used) FM Deviation (Limiter) Adjustment Line-in Level Adjustment 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.4.6 3.4.7 3.3 3.3 3.4 3.5 3.5 3.5 3.5 3.6 3.7 3.7 3.7 Copyright TEL 29/02/00 C3.2 T856/857 Initial Tuning & Adjustment Section Title 3.5.1 3.5.2 Audio Processor Links Link Details Typical Options Synthesiser Alignment PA Alignment (T856 Only) Thermal Shutdown (T856 Only) 3.5 3.6 3.7 3.8 3.9 3.9.1 3.9.2 3.9.3 3.9.4 3.9.5 3.9.6 3.9.6.1 3.9.6.2 3.9.6.3 Figure 3.1 3.2 Audio Processor & CTCSS Two Point Modulation Modulator Adjustment CTCSS Encoder (If Used) Limiter Adjustment Line Level Without Compressor Compressor Compressor On Line Input Only Compressor On Microphone Input Only Compressor On Both Line & Microphone Inputs Title T856/857 Test Equipment Set-up With T800-01-0010 T856/857 Test Equipment Set-up Without T800-01-0010 M850-00 Page 3.8 3.8 3.8 3.9 3.10 3.10 3.11 3.11 3.11 3.12 3.12 3.13 3.13 3.13 3.13 3.14 Page 3.4 3.4 29/02/00 Copyright TEL M850-00 T856/857 Initial Tuning & Adjustment C3.3 3.1 Introduction When you receive your T856 transmitter or T857 exciter it will be run up and working on a particular frequency (the "default channel")1. If you want to switch to a frequency that is within the 8MHz switching range (i.e. 4MHz from the factory programmed fre-

quency), you should only need to reprogram the transmitter/exciter with the PGM800Win software (refer to the PGM800Win programming kit and Section 3.2 below). However, if you want to switch to a frequency outside the 8MHz switching range, you will have to reprogram and re-tune the transmitter/exciter to ensure correct operation. In this case you should carry out the short tuning procedure described in Section 3.4. If you have carried out repairs or other major adjustments, you must carry out the full tuning and adjustment procedure described in this section (except for Section 3.4). 3.2 Channel Programming You can program up to 128 channel frequencies into the transmitter/exciters EEPROM memory (IC820) by using the PGM800Win software package and an IBM PC. You can also use PGM800Win to select the transmitter/exciters current operating frequency (or

"default channel"). If the transmitter/exciter is installed in a rack frame, you can program it via the pro-

gramming port in the speaker panel. However, you can also program the transmitter/

exciter before it is installed in a rack frame as follows:

by using a T800-01-0010 calibration test unit;

via D-range 1;

via D-range 2 (standard T800-03-0000 auxiliary D-range only);

via SK805 (internal Micromatch connector). If you do not use the T800-01-0010, you will have to connect the PC to the transmitter/

exciter via a module programming interface (such as the T800-01-0004). For a full description of the channel programming procedure, refer to the PGM800Win programming software users manual. Note:

When an auxiliary D-range kit (D-range 2 - T800-03-0000) is fitted, you can also select a channel with an external switch, such as the DIP switch on the rack frame backplane PCB. Refer to Part C in the T800 Series Ancillary Equipment Service Manual (M800-00-101 or later issue) or consult your nearest Tait Dealer or Customer Service Organisation for further details. 1. Use the "Read Module" function in PGM800Win to find out what the default channel is. Copyright TEL 31/09/98 C3.4 3.3 T856/857 Initial Tuning & Adjustment M850-00 Test Equipment Required You will need the following test equipment:

computer with PGM800Win installed T800 programming kit module programming interface (e.g. T800-01-0004 - optional) 13.8V power supply digital multimeter audio signal generator RF power meter audio voltmeter x 2 modulation meter oscilloscope (digital preferred) 20dB or 40dB pad T800-01-0010 calibration test unit (optional) or RF test set (optional) Figure 3.1 and Figure 3.2 show typical test equipment set-ups. PSU

+13.8V

-Ve 20dB pad: exciter 40dB pad: transmitter Frequency Counter 600 Audio Generator Line I/P CTCSS I/P T800 Calibration Test Unit Exciter/

Transmitter RF O/P Modulation Meter AF O/P Audio Voltmeter PGM800Win RF Power Meter Audio Voltmeter Oscilloscope Figure 3.1 T856/857 Test Equipment Set-up With T800-01-0010 PSU

+13.8V

-Ve 20dB pad: exciter 40dB pad: transmitter Frequency Counter 600 Audio Generator Line I/P CTCSS I/P Exciter/

Transmitter RF O/P Key Modulation Meter AF O/P Audio Voltmeter PGM800Win RF Power Meter Audio Voltmeter Oscilloscope Serial Com via module programming interface

(e.g. T800-01-0004) Figure 3.2 T856/857 Test Equipment Set-up Without T800-01-0010 31/09/98 Copyright TEL W W M850-00 T856/857 Initial Tuning & Adjustment C3.5 3.4 Short Tuning Procedure Use this procedure only if you want to reprogram the T856/857 to a frequency outside the 8MHz switching range and do not intend to carry out any other major adjustments or repairs. 3.4.1 Introduction Reprogram the operating frequency as described in the PGM800Win program-

ming kit (refer to Section 3.2). Remove the top cover (nearest the handle). Set up the test equipment as described in Section 3.3. Set the links in the audio processor section as required (refer to Section 3.5). 3.4.2 Synthesiser Alignment Connect a high impedance voltmeter to the long lead of L1 in the VCO (this meas-

ures the synthesiser loop voltage). Key the transmitter by earthing the Tx-Key line. Single Channel Multichannel Tune VCO trimmer C6 for a synthesiser loop voltage of 10V. Tune VCO trimmer C6 for a synthesiser loop voltage of 10V on the middle channel. If there is no middle channel, tune C6 so that the channels are symmetrically placed around a loop voltage of 10V. All channels should lie within the upper and lower limits of 16V and 3V respectively. Do not attempt to program channels with a greater fre-

quency separation than the specified switching range of 8MHz. 3.4.3 Output Power Adjustment (T856 Only) Connect an RF power meter with suitable attenuation to the output socket and key the transmitter. Turn RV310 (power control) fully clockwise. Tune #CV475 (output power trim) for maximum output power and check that this is >30W. Adjust RV310 for the required output power (between 5 and 25W). Readjust #CV475 to reduce the supply current by up to 0.5A. Copyright TEL 29/02/00 C3.6 T856/857 Initial Tuning & Adjustment M850-00 3.4.4 Two Point Modulation Adjustment Note 1:

Note 2:

Note 3:

In this and following sections deviation settings are given first for wide bandwidth sets, followed by settings in brackets for mid bandwidth sets ( ) and narrow bandwidth sets [ ]. The reference modulation and limiter adjustments are controlled by 256-

step electronic potentiometers (EPOTs), which are adjusted via the Refer-

ence Modulation and Deviation settings in PGM800Win. This allows the two point modulation and deviation settings to be adjusted for each chan-

nel. To optimise the modulation response across the switching range, repeat steps 1-4 below for each channel that will be used (usually needed only for data applications). In applications where the modulation response is less critical (e.g. voice use only), carry out steps 1-4 below on the middle channel and use the EPOT Fill option1 in PGM800Win to copy the value to the other channels. Note 4:

If you are using an RF test set, turn the low pass filter off and set the high pass filter to 15kHz before beginning this procedure. 1. 2. 3. 4. Inject an audio signal of 300Hz 1.5V rms (+5dBm) into the CTCSS input (D-range 1 (PL100) pin 8). Key the transmitter by earthing the Tx-Key line. Adjust the output from the audio generator to obtain 3kHz (2.4kHz) [1.5kHz]

deviation at 300Hz. Change the input frequency to 100Hz and, using PGM800Win, adjust the value of the Reference Modulation EPOT setting for the current channel to obtain 3kHz

(2.4kHz) [1.5kHz] deviation (you can use either the mouse or up and down arrow keys). Change the input frequency back to 300Hz. Repeat steps 2 and 3 above until the deviations achieved at the two input frequen-

cies are within 0.2dB of each other. You will need to do this at least four times. 5. Sweep the audio between 50 and 300Hz for peaks. Note:

A peak between 50 and 300Hz will indicate a fault condition, i.e:

- incorrect set-up

- modulation circuitry fault. or The specification window is 1dB relative to 150Hz from 67 to 260Hz. 1. Use the EDIT FILL button on the tool bar or go to Edit, Fill, Epot Settings on the menu bar. 29/02/00 Copyright TEL M850-00 T856/857 Initial Tuning & Adjustment C3.7 3.4.5 CTCSS Encoder (If Used) Program a CTCSS tone on the default channel using PGM800Win. If you are using an RF test set, turn off the 300Hz high pass filter. Key the T856/857 with the front panel "Carrier" switch. Adjust RV805 (CTCSS level adjust) to give 500Hz (350Hz) [250Hz] deviation. Set the maximum deviation as per Section 3.4.6. 3.4.6 Note:

FM Deviation (Limiter) Adjustment If the T856/857 will be used over the whole 8MHz switching range, you must set the deviation for each channel. However, if the module will be used on frequencies that cover only a 1MHz (or less) switching range, you can set the deviation on the middle channel and use this value for all other channels with the EPOT Fill option in PGM800Win. Inject 1kHz at -10dBm into the line input (D-range 1 (PL100) pins 1 & 4; pins 2 & 3 shorted; refer to Section 2.2 of Part F). Adjust RV210 (line sensitivity) fully clockwise and key the transmitter by earthing the Tx-Key line. Using PGM800Win, adjust the value of the Deviation EPOT setting for the current channel to obtain a deviation limit of 4.7kHz (3.8kHz)

[2.3kHz] (you can use either the mouse or up and down arrow keys). Sweep the audio frequency from 100Hz to 4kHz and ensure that the maximum deviation does not exceed 4.7kHz (3.8kHz) [2.3kHz]. Readjust Deviation if necessary via PGM800Win. 3.4.7 Line-in Level Adjustment Remove the CTCSS signal (if used). Set the injected signal at the line input to the required line level (typically -10 to

-20dBm). Adjust RV210 (line sensitivity) to provide 3kHz (2.4kHz) [1.5kHz] deviation. Reapply the CTCSS signal (if required). Copyright TEL 29/02/00 C3.8 3.5 T856/857 Initial Tuning & Adjustment M850-00 Audio Processor Links 3.5.1 Link Details Use the following table to set up the audio processor to the configuration you require. You should set the audio processor links before carrying out any of the tuning and adjustment procedures. The factory settings are shown in brackets [ ]. Plug Linka Function PL205 PL210 PL215 PL220 1-2

[3-4]

5-6

[1-2]

3-4 5-6 1-2

[3-4]

5-6 7-8 9-10 1-2

[3-4]

5-6 A B C L M N G H I J K D E F not connected microphone pre-amp. output to compressor input microphone pre-amp. output to multiplexer input multiplexer output to pre-emphasis input multiplexer output to limiter input multiplexer output to compressor input not connected compressor output to multiplexer input compressor output to limiter input compressor output to pre-emphasis input not connected pre-emphasis output to multiplexer input pre-emphasis output to limiter input not connected a. The letters in this column and in the table in Section 3.5.2 below refer to the identification letters screen printed onto the PCB beside each pair of pins. 3.5.2 Typical Options microphone pre-amp. compressed and pre-emphasised;

line input pre-emphasised

(standard set-up) microphone pre-amp. compressed and pre-emphasised;

line input unprocessed line and microphone compressed and pre-emphasised microphone pre-amp. compressed;

line and microphone flat response PL205 PL210 PL215 PL220

[3-4]

B

[1-2]

L

[3-4]

H

[3-4]

E 3-4 B 5-6 C 3-4 B 3-4 M 5-6 N 3-4 M 7-8 J 7-8 J 3-4 H 1-2 D 3-4 E 5-6 F 31/09/98 Copyright TEL M850-00 T856/857 Initial Tuning & Adjustment C3.9 3.6 Synthesiser Alignment Ensure that the T856/857 has been programmed with the required frequencies using PGM800Win software. Single Channel Multichannel Select a channel using PGM800Win. Select the middle channel via PGM800Win. Connect a high impedance voltmeter to the long lead of L1 in the VCO (this meas-

ures the synthesiser loop voltage). Key the transmitter by earthing the Tx-Key line. Single Channel Multichannel Tune VCO trimmer C6 for a synthesiser loop voltage of 10V. Tune VCO trimmer C6 for a synthesiser loop voltage of 10V on the middle channel. If there is no middle channel, tune C6 so that the channels are symmetrically placed around a loop voltage of 10V. All channels should lie within the upper and lower limits of 16V and 3V respectively. Do not attempt to program channels with a greater fre-

quency separation than the specified switching range

(8MHz). Check that the exciter output power is 1W 300mW (T857 only). Measure the exciter output frequency and adjust the TCXO (=IC700) trimmer if required. Caution:

This trimmer is susceptible to physical damage. Do not exert a down-

ward force of more than 500g (1lb) when adjusting. Copyright TEL 31/09/98 C3.10 T856/857 Initial Tuning & Adjustment M850-00 3.7 PA Alignment (T856 Only) Check that the exciter is connected to the PA with the coaxial link. Connect an RF power meter to the PA output (use an appropriate attenuator as necessary). Turn RV310 (power control) fully clockwise. Note:

Before the following measurement is taken, ensure the heatsink is at ambi-

ent temperature (20-25C). Measure and record the voltage (VL) at L481; perform this measurement at room temperature so that the NTC (R481) is close to 25 C. Key the transmitter by earthing the Tx-Key line. Tune #CV475 until maximum power is obtained. Check that the power exceeds 30W. Adjust RV310 (power control) to 25W. Readjust #CV475 to reduce the supply current by up to 0.5A. 3.8 Thermal Shutdown (T856 Only) Key the transmitter by earthing the Tx-Key line and set the output power to 25W as described in Section 3.7. Short L481 to ground. Set RV330 (shutdown power level) for an output power of 5W. Set RV320 (shutdown temperature) to 0.16VL volts (measured at IC350 pin 3), where VL is the voltage measured at L481 in Section 3.7. This sets the thermal shutdown at 85 C at NTC R481. 31/09/98 Copyright TEL M850-00 T856/857 Initial Tuning & Adjustment C3.11 3.9 Audio Processor & CTCSS 3.9.1 Two Point Modulation The T856 and T857 utilise two point modulation to obtain a wide audio bandwidth independent of the synthesiser loop filter response. This is achieved by simultaneously frequency modulating the VCO and phase modulating the synthesiser reference fre-

quency. The relative signal levels fed to the two modulators are quite critical and cause interaction when setting up. Both modulating signals require readjustment when the exciter is shifted in frequency greater than the switching range (i.e. D F>4MHz). Note 1:

Note 2:

Note 3:

In this and following sections deviation settings are given first for wide bandwidth sets, followed by settings in brackets for mid bandwidth sets ( ) and narrow bandwidth sets [ ]. The reference modulation and limiter adjustments are controlled by 256-

step electronic potentiometers (EPOTs), which are adjusted via the Refer-

ence Modulation and Deviation settings in PGM800Win. This allows the two point modulation and deviation settings to be adjusted for each chan-

nel. To optimise the modulation response across the switching range, repeat steps 1-4 below for each channel that will be used (usually needed only for data applications). In applications where the modulation response is less critical (e.g. voice use only), carry out steps 1-4 below on the middle channel and use the EPOT Fill option1 in PGM800Win to copy the value to the other channels. Note 4:

If you are using an RF test set, turn the low pass filter off and set the high pass filter to 15kHz before beginning this procedure. 3.9.2 Modulator Adjustment 1. 2. 3. Inject an audio signal of 300Hz 1.5V rms (+5dBm) into the CTCSS input (D-range 1 (PL100) pin 8). Key the transmitter by earthing the Tx-Key line. Adjust the output from the audio generator to obtain 3kHz (2.4kHz) [1.5kHz]

deviation at 300Hz. Change the input frequency to 100Hz and, using PGM800Win, adjust the value of the Reference Modulation EPOT setting for the current channel to obtain 3kHz

(2.4kHz) [1.5kHz] deviation (you can use either the mouse or up and down arrow keys). 1. Use the EDIT FILL button on the tool bar or go to Edit, Fill, Epot Settings on the menu bar. Copyright TEL 29/02/00 C3.12 T856/857 Initial Tuning & Adjustment M850-00 4. Change the input frequency back to 300Hz. Repeat steps 2 and 3 above until the deviations achieved at the two input frequen-

cies are within 0.2dB of each other. You will need to do this at least four times. 5. Sweep the audio between 50 and 300Hz for peaks. Note:

A peak between 50 and 300Hz will indicate a fault condition, i.e:

- incorrect set-up

- modulation circuitry fault. or The specification window is 1dB relative to 150Hz from 67 to 260Hz. 3.9.3 CTCSS Encoder (If Used) Program a CTCSS tone on the default channel using PGM800Win. If you are using an RF test set, turn off the 300Hz high pass filter. Key the T856/857 with the front panel "Carrier" switch. Adjust RV805 (CTCSS level adjust) to give 500Hz (350Hz) [250Hz] deviation. Set the maximum deviation as per Section 3.9.4. 3.9.4 Note:

Limiter Adjustment If the T856/857 will be used over the whole 8MHz switching range, you must set the deviation for each channel. However, if the module will be used on frequencies that cover only a 1MHz (or less) switching range, you can set the deviation on the middle channel and use this value for all other channels with the EPOT Fill option in PGM800Win. Set the links in the audio processor section as required (refer to Section 3.5). Inject 1kHz at -10dBm into the line input (D-range 1 (PL100) pins 1 & 4; and pins 2

& 3 shorted; refer to Section 2.2 of Part F). Adjust RV210 (line sensitivity) fully clockwise and key the transmitter by earthing the Tx-Key line. Using PGM800Win, adjust the value of the Deviation EPOT setting for the current channel to obtain a deviation limit of 4.7kHz (3.8kHz)

[2.3kHz] (you can use either the mouse or up and down arrow keys). Sweep the audio frequency from 100Hz to 4kHz and ensure that the maximum deviation does not exceed 4.7kHz (3.8kHz) [2.3kHz]. Readjust Deviation if necessary via PGM800Win. 29/02/00 Copyright TEL M850-00 T856/857 Initial Tuning & Adjustment C3.13 3.9.5 Line Level Without Compressor This section assumes that the compressor is not used. If the compressor is required, refer to Section 3.9.6. Remove the CTCSS signal (if used). Adjust the line sensitivity as follows:

set the injected signal at the line input to the required line level (typically -10 to

-20dBm);

adjust RV210 (line sensitivity) to provide 3kHz (2.4kHz) [1.5kHz] devia-

tion. Reapply the CTCSS signal (if required). 3.9.6 Compressor The compressor may be used on the line input only, the microphone input only, or on both the line and microphone inputs. If the compressor is used, refer to one of the fol-

lowing sections as appropriate. 3.9.6.1 Compressor On Line Input Only Set RV210 (line sensitivity) fully clockwise and key the transmitter by earthing the Tx-Key line. Reduce the line level to -50dBm at 1kHz and set RV220 (compression level) fully clockwise. Check that 3kHz deviation (2.4kHz) [1.5kHz] is still available. Slowly increase the audio input level until the demodulated waveform shows sig-

nificant signs of clipping (approximately 4.5kHz (3.6kHz) [2.3kHz] deviation). Adjust RV220 anticlockwise until the demodulated waveform is just clipping

(approximately 4kHz (3.2kHz) [2kHz] deviation). Increase the input level to -10dBm and check that the test tone is still held just into clipping. The input line level should be typically -10 to -20dBm. 3.9.6.2 Compressor On Microphone Input Only Key the transmitter by earthing the Tx-Key line and plug a microphone jack into the front panel socket. Adjust RV220 (compression level) fully clockwise. Acoustically couple the microphone to a tone box (1kHz) and close the PTT switch. Copyright TEL 29/02/00 C3.14 T856/857 Initial Tuning & Adjustment M850-00 Increase the audio level until the demodulated waveform shows significant signs of clipping (approximately 4.5kHz (3.6kHz) [2.3kHz] deviation). Adjust RV220 anticlockwise until the demodulated waveform is just clipping

(approximately 4kHz (3.2khz) [2kHz] deviation). Increase the audio level by 10dB and verify that the test tone is held just into clip-

ping. Whistle steadily into the microphone, checking that approximately 4kHz

(3.2khz) [2kHz] deviation is produced. The modulated waveform should be basically sinusoidal. Speak into the microphone, checking that the modulation peaks reach about 5kHz (4kHz) [2.5kHz] deviation. As the line is to be used without compression, set RV210 (line sensitivity) as described in Section 3.9.5. 3.9.6.3 Compressor On Both Line & Microphone Inputs Set up as described in Section 3.9.6.1. 29/02/00 Copyright TEL M850-00 4 Caution:

T856/857 Functional Testing C4.1 T856/857 Functional Testing This equipment contains CMOS devices which are susceptible to dam-

age from static charges. Refer to Section 1.2 in Part A for more infor-

mation on anti-static procedures when handling these devices. The following test procedures will confirm that the T856/857 has been tuned and adjusted correctly and is fully operational. Note 1:

Note 2:

In this and following sections deviation settings are given first for wide bandwidth sets, followed by settings in brackets for mid bandwidth sets ( ) and narrow bandwidth sets [ ]. Unless otherwise specified, the term "PGM800Win" used in this and follow-

ing sections refers to version 2.00 and later of the software. Refer to Figure 4.4 and Figure 4.5 for the location of the main tuning and adjustment controls, and to Section 3.3 for the test equipment set-up. Refer also to Section 6 where the parts lists, grid reference index and diagrams will provide detailed information on identifying and locating components and test points on the main PCB. The parts list and diagrams for the VCO PCB are in Part E. The following topics are covered in this section. Section Title 4.1 4.2 4.3 4.4 4.5 4.6 Current Consumption Output Power Output Frequency Timers Frequency Response Audio Level Input Sensitivity Figure 4.1 4.2 4.3 4.4 4.5 Title T856/857 Transmit Timers T856/857 Pre-emphasis Response T856/857 Limiting Response T856 Main Tuning & Adjustment Controls T857 Main Tuning & Adjustment Controls Page 4.3 4.3 4.3 4.3 4.4 4.7 Page 4.4 4.5 4.6 4.9 4.11 Copyright TEL 31/09/98 C4.2 T856/857 Functional Testing M850-00 31/09/98 Copyright TEL M850-00 T856/857 Functional Testing C4.3 4.1 Current Consumption Connect the T856/857 to a 13.8V power supply. Connect an RF power meter to the T856/857 output socket. Check that the current in the 13.8V power cable is less than 150mA. Key the T856/857 by earthing the Tx-Key line (the carrier "On" LED should light). T856 Only:

Adjust RV310 (power control) to obtain 25W output power. Check that the current is as follows:

T856 T857

<5.5A

<750mA. 4.2 Output Power Connect an RF power meter with suitable attenuation to the T856/857 output socket. Key the T856/857 by earthing the Tx-Key line. Check that:

T856 T857 the output power adjusts to 25W with RV310 (power control) turned fully clockwise the output power is 1W 300mW. 4.3 Output Frequency Connect the T856/857 output to a frequency counter via an attenuator pad:

T856 T857 40dB pad 20dB pad. Measure the output frequency and, if necessary, adjust the TCXO (=IC700) to trim to the nominal frequency (100Hz). 4.4 Timers The transmit tail timer, transmit timeout timer and transmit lockout timer can all be set from PGM800Win. The fields for setting these are found on the system information page. These three timers operate as follows (refer also to Figure 4.1):

Copyright TEL 31/09/98 C4.4 T856/857 Functional Testing M850-00 Timer Transmit Tail Transmit Timeout Transmit Lockout Function Sets the tail time during which the transmitter stays keyed after the exter-

nal key source has been removed. Sets the maximum continuous trans-

mission time. Once the timer has timed out, the transmitter must be keyed again, unless prevented by the transmit lockout timer. Sets the period of time that must elapse after a timeout before the trans-

mitter can re-transmit. Once the timer has timed out, the transmitter can be keyed again. Adjustment 0-5 seconds in 100ms stepsa 0-300 secondsb in 10 second steps 0-60 seconds in 10 second steps a. Adjustable in 20ms steps in PGM800Win version 2.12 and later. b. Adjustable in 20ms steps in PGM800Win version 2.12 and later. Tx-Enable On Tx-Reg. Tx-Enable On Tx-Reg. Tail Time Lockout Time Timeout Time Figure 4.1 T856/857 Transmit Timers 4.5 Frequency Response If the T856/857 has been correctly adjusted, the pre-emphasis and limiting responses should closely match those shown in Figure 4.2 and Figure 4.3 respectively. Note:

The limits shown on these graphs should not be exceeded. If you are using an RF test set, turn off all filters. Measure the pre-emphasis response as follows:

Reduce the line level to give 1kHz (0.8kHz) [0.5kHz] deviation at 1kHz. Sweep the modulation frequency. The response should closely match that shown in Figure 4.2. Measure the limiting response as follows:

Set the line level to give 3kHz (2.4kHz) [1.5kHz] deviation at 1kHz. 29/02/00 Copyright TEL M850-00 T856/857 Functional Testing C4.5 Increase the line level 20dB and sweep the modulation frequency. The response should closely match that shown in Figure 4.3. Wide Bandwidth Peak + max. dev. = +1.0kHz @ 1000Hz Peak - max. dev. = -1.0kHz @ 1000Hz

+10

+8

+6

+4

+2

+0

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

) z H k 1

. v e d o t

. f e r B d

l e v e L n o i t a u d o M l 100 200 300 500 1k 2k 3k 5k 10k Frequency (Hz) Mid Bandwidth The mid bandwidth graph is the same shape as the wide bandwidth graph. The devia-

tion figures are as follows:

peak + max. deviation = +0.8kHz peak - max. deviation = -0.8kHz. Narrow Bandwidth Peak + max. dev. = +0.5kHz @ 1000Hz Peak - max. dev. = -0.5kHz @ 1000Hz

+10

+8

+6

+4

+2

+0

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

) z H k 1

. v e d o t

. f e r B d

l e v e L n o i t a u d o M l 100 200 300 500 1k 2k 3k 5k 10k Frequency (Hz) Figure 4.2 T856/857 Pre-emphasis Response Copyright TEL 29/02/00 C4.6 T856/857 Functional Testing M850-00 Wide Bandwidth Peak + max. dev. = +4.9kHz @ 1500Hz Peak - max. dev. = -4.4kHz @ 2500Hz Above limiting (steady-state)

+10

+8

+6

+4

+2

+0

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

. v e d

. x a m o t

. f e r B d

l e v e L n o i t a u d o M l 10 20 30 50 100 300 200 500 Frequency (Hz) 1k 2k 3k 5k 10k Mid Bandwidth The mid bandwidth graph is the same shape as the wide bandwidth graph. The devia-

tion figures are as follows:

peak + max. deviation = +4kHz peak - max. deviation = -4kHz. Narrow Bandwidth Peak + max. dev. = +2.4kHz @ 2000Hz Peak - max. dev. = -2.5kHz @ 2000Hz Above limiting (steady-state)

+10

+8

+6

+4

+2

+0

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

. v e d

. x a m o t

. f e r B d

l e v e L n o i t a u d o M l 10 20 30 50 100 300 200 500 Frequency (Hz) 1k 2k 3k 5k 10k Figure 4.3 T856/857 Limiting Response 31/09/98 Copyright TEL M850-00 T856/857 Functional Testing C4.7 4.6 Audio Level Input Sensitivity Adjust RV210 (line sensitivity) fully clockwise. Check that the input sensitivities are better than those specified below:

Line Input 600 ohms, 3kHz (2.4kHz) [1.5kHz] deviation at 1kHz:

with compressor without compressor

-50dBm

-30dBm Microphone Input 600 ohms, 3kHz (2.4kHz) [1.5kHz] deviation at 1kHz:

with compressor without compressor

-75dBm

-55dBm CTCSS Input 1kHz deviation at 150Hz 500mV rms Note:

A degraded signal to noise ratio can be expected with the compressor selected. The extent of the degradation is dependent on the audio input level. Copyright TEL 31/09/98 C4.8 T856/857 Functional Testing M850-00 31/09/98 Copyright TEL M850-00 5 Caution:

T856/857 Fault Finding C5.1 T856/857 Fault Finding This equipment contains CMOS devices which are susceptible to dam-

age from static charges. Refer to Section 1.2 in Part A for more infor-

mation on anti-static procedures when handling these devices. The following test procedures and fault finding flow charts may be used to help locate a hardware problem, however they are by no means a complete fault finding procedure. If you still cannot trace the fault after progressing through them in a logical manner, contact your nearest Tait Dealer or Customer Service Organisation. If necessary, you can get additional technical help from Customer Support, Radio Systems Division, Tait Electronics Ltd, Christchurch, New Zealand (full contact details are on page 2). Note 1:

Note 2:

In this and following sections deviation settings are given first for wide bandwidth sets, followed by settings in brackets for mid bandwidth sets ( ) and narrow bandwidth sets [ ]. Unless otherwise specified, the term "PGM800Win" used in this and follow-

ing sections refers to version 2.00 and later of the software. Refer to Section 6 where the parts lists, grid reference index and diagrams will provide detailed information on identifying and locating components and test points on the main PCB. The parts list and diagrams for the VCO PCB are in Part E. The following topics are covered in this section Section Title Page 5.1 5.2 5.3 5.4 5.5 5.4.1 5.4.2 5.5.1 5.5.2 5.5.3 5.5.4 Visual Checks Component Checks Front Panel LED Indicator DC Checks Power Rails VCO Locking RF Checks T856 Drive Power T856 PA Output Power T857 Output Power Audio And Modulation 5.6 PGM800Win Generated Errors 5.3 5.3 5.3 5.4 5.4 5.4 5.5 5.5 5.5 5.5 5.6 5.7 Copyright TEL 31/09/98 C5.2 T856/857 Fault Finding Section 5.7 5.7.1 5.7.1.1 5.7.1.2 5.7.1.3 5.7.2 5.7.3 5.7.4 5.7.5 5.7.6 5.7.7 Title Fault Finding Charts Microcontroller Basic Checks Serial Communications CTCSS Encode Regulator Synthesiser T856 Drive Amplifier T856 PA & Power Control T857 Exciter Drive Amplifier Audio Processor 5.8 To Replace The T856 PA Transistors (Q410 & Q420) Figure 5.1 5.2 Title RF Diode Probe Circuit Typical Transistor/Capacitor Spacing (Not To Scale) M850-00 Page 5.8 5.8 5.8 5.9 5.10 5.11 5.12 5.15 5.16 5.17 5.18 5.19 Page 5.5 5.19 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.3 5.1 Visual Checks Remove the covers from the T856/857 and inspect the PCB for damaged or broken com-

ponents, paying particular attention to the surface mounted devices (SMD's). Check for defective solder joints. If repair or replacement is considered necessary, refer to Section 3 of Part A. 5.2 Component Checks If you suspect a transistor is faulty, you can assess its performance by measuring the for-

ward and reverse resistance of the junctions. Unless the device is completely desol-

dered, first make sure that the transistor is not shunted by some circuit resistance. Use a good quality EVM (e.g. Fluke 75) for taking the measurements (or a 20k ohm/V or bet-

ter multimeter, using only the medium or low resistance ranges). The collector current drawn by multi-junction transistors is a further guide to their per-

formance. If an IC is suspect, the most reliable check is to measure the DC operating voltages. Due to the catastrophic nature of most IC failures, the pin voltages will usually be markedly different from the recommended values in the presence of a fault. The recommended values can be obtained from either the circuit diagram or the component data catalogue. 5.3 Front Panel LED Indicator The green "Supply" LED on the T856/857 front panel will flash according to the condi-

tions described in the following table:

Flash Rate Condition fast unequal

(
sec. on/
sec. off approx.) T856/857 is linked with PGM800Win

(
sec. on/1 sec. off approx.) microcontroller has detected an internal communications error -

refer to Section 5.7.1 Where two or more conditions occur at the same time, the precedence is in the order shown above (i.e. T856/857 linked has the highest priority, followed by internal error). Copyright TEL 31/09/98 C5.4 5.4 T856/857 Fault Finding DC Checks 5.4.1 Power Rails M850-00 Refer to the test points and options diagrams in Section 6 for test point locations, and to the regulator fault finding chart (Section 5.7.2) for fault diagnosis. Check the 13.8V (TP601) and 9V (TP602) supplies at their test points in the regula-

tor compartment with a DMM. Check the 5V (TP604) and 20V (TP603) rails at their respective test points in the regulator compartment. Check that Tx-Reg. (TP305 in the exciter compartment) comes up to 8.8V when the exciter is keyed. Check the +5V digital regulator output (TP607 in the regulator compartment). T856 Only:

Check the 9V supply (IC370 pin 1) with a DMM. Check for short circuits. 5.4.2 VCO Locking Key the exciter. Using a DMM, monitor the VCO control voltage on the long lead of L1 on the VCO PCB. If the synthesiser is locked and the VCO aligned, the voltage at this point should be between 3 and 16V. If the VCO is not locked, refer to the synthesiser fault finding chart (Section 5.7.3). 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.5 5.5 RF Checks In-circuit RF levels may be measured with an RF probe on which the earth lead has been shortened to a minimum (i.e. 13mm). Refer to the circuit diagrams for typical levels. Figure 5.1 shows a suitable RF probe circuit.. Probe 1n 10k Coax DC to DVM or Oscilloscope Earthing Clip 1N6263 1n 100k This unit is not suitable for use on high power RF circuits. Figure 5.1 RF Diode Probe Circuit 5.5.1 T856 Drive Power Refer to the drive amplifier fault finding chart (Section 5.7.4). Ensure that the VCO locks (refer to Section 5.4.2). Connect the drive output to a power meter and key the transmitter. Check that the exciter output power (SK310) is >1.5W. Note:

If the synthesiser is out of lock, the lock detector (synthesiser IC740 and comparator IC750) will prevent the RF signal from reaching the PA by switching the supply to the exciter amplifier (Q350, Q355). 5.5.2 T856 PA Output Power Reconnect the drive output to the PA input. Connect the PA to a power meter and key the transmitter. Check that the output power is >30W with RV310 (power control) adjusted fully clockwise. 5.5.3 T857 Output Power Refer to the exciter drive amplifier fault finding chart (Section 5.7.6). Ensure that the VCO locks (refer to Section 5.4.2). Copyright TEL 31/09/98 C5.6 T856/857 Fault Finding M850-00 Connect the exciter output to a power meter and key the exciter. Check that the output power is 1W 300mW. Note:

If the synthesiser is out of lock, the lock detector (synthesiser IC740 and comparator IC750) will prevent the RF signal from reaching the PA by switching the supply to the exciter amplifier (Q301, IC300, Q302, Q303). 5.5.4 Audio And Modulation Refer to the audio processor fault finding chart (Section 5.7.7). Set up the audio processor as described in Section 3.9. Check that the demodulated RF output has the frequency response referred to in Section 4.5 with at least 5kHz (4kHz) [2.5kHz] deviation available at 1kHz modulating frequency. If the above result is not achieved, either the two modulators are incorrectly adjusted or a fault condition exists. 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.7 5.6 PGM800Win Generated Errors The following errors are those most likely to occur using PGM800Win. Refer to the PGM800Win software users manual for a complete list of error messages. Channel Switch Set The programmed default channel change was not accepted by the base station because a channel is selected externally. Try turning the external channel switch off to change the default channel in PGM800Win. Synth Out Of Lock The synthesiser received incorrect data, or the data was corrupted. Enter a frequency within the VCO switching range, or tune the VCO. Internal Error Data could not be read from the base station due to an internal error. Check for shorts or open circuits on the SDA, SCK, SYNTH and EPOT lines. The SDA, SCK and SYNTH are normally high, and the EPOT is normally low. Write/Read To An Unlinked Module The link to the module does not exist. Undefined error. Copyright TEL 31/09/98 C5.8 5.7 Note:

T856/857 Fault Finding Fault Finding Charts M850-00 The standard test point designations used in this section are as follows:

TP601 TP602 TP603 TP604 13.8V 9V 20V 5V 5.7.1 Microcontroller (IC810) 5.7.1.1 Basic Checks Is the 12.8MHz clock present on IC810 pin 21

(microcontroller)?

N Check IC740

(synthesiser). Y Replace IC810. N Is pin 30 pulsing?

Y Pulsing Check the state of pin 10. Low High or open circuit Use a DSO* to check operation of IC650

(i.e. active high pulse at power up).

*digital storage oscilloscope Replace IC650. Check state of pins 36 to 43. Pulsing Check state of pin 35. High Replace IC810. Static high/low Low/floating Replace IC810. Correct the fault causing pin 35 to be low/floating. 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.9 5.7.1.2 Serial Communication Disconnect the programming lead. Is IC810 pin 11 high?

(microcontroller) Y Connect the programming lead and use PGM800Win to read the rack/radio. Check I/O pad P810 with a DSO*. Does it swing from 0 to 5V?

N Check pin state. Low/floating Check the transistor interface circuitry. Noise on pin Check the SERIAL-COM and AUDIO-1/2 links. N Check the transistor interface circuitry and/or replace the programming lead.

*digital storage oscilloscope Y Use PGM800Win to send a POLL command to the radio. Check IC810 pin 13 with a DSO. Is there a response from IC810 after a poll command is sent?

N Replace IC810. Y Check the transistor interface circuitry and/or replace the programming lead. Copyright TEL 31/09/98 C5.10 T856/857 Fault Finding M850-00 5.7.1.3 CTCSS Encode Use PGM800Win to select a channel with a CTCSS tone programmed. Y Check IC810 pins 24, 25

& 26 (microcontroller). Are there 5V square waves at the CTCSS frequency?

Y Check IC830 pins 1, 7 & 14. Are there 9V square waves at the CTCSS frequency?

Y Cannot select a channel Check serial communications.

(See separate flow chart). No square waves or uneven mark/space ratio Replace IC810. No square waves or uneven mark/space ratio Check IC830 circuitry and repair/replace. Check IC830 pin 8. Is there a sine wave at the CTCSS frequency?

No tone Distorted tone Check RV805. Check the filter circuit for bias problems and/or short circuits. 31/09/98 Copyright TEL M850-00 5.7.2 Regulator T856/857 Fault Finding C5.11 Check for overheating components &

short circuits. N N 13.8V present on IC630 pin 3?

Y 5.3V present on IC630 pin 1?

Y N N 9.0V present on TP602?

Y 20V present on TP603?

Y

+5V present on IC610 pin 2?

N Y Key Tx. Y Y 8.8V present on Tx reg. TP305?

N 0V present on Q860 collector?

N 0.6V present on Q860 base?

Y N Check continuity from pin 9 of D-range 1. Replace IC630. Check Q630, Q620 & IC640. Check Q660 is switching at approx. 150kHz. Check R615. Replace IC610. Regulators OK. Replace Q610. Check Q860 and associated circuitry. Regulators OK. Check microcontroller section. Copyright TEL 31/09/98 C5.12 T856/857 Fault Finding M850-00 5.7.3 Synthesiser Refer to the synthesiser circuit diagram (sheet 7) in Section 6 and the VCO circuit dia-

gram in Part E. B VCO out of lock.

+5V present at IC700, IC710, IC740, IC720

& IC730?

N Y N N N 20V present on IC750 pin 8?

Y 9V present on Q795 divider buffer?

Y DC V present on Q795 emitter?

Y Check 5V reg. &

supply resistor to each IC. 20V inverter supply faulty. Check 9V supply. Check biasing resistors & Q795. Does VCO trimmer adjust for stable control line between 3 & 16V?

Recheck programming via PGM800Win. Y VCO freq. correct?

N Y Does VCO trimmer adjust for required frequency range between 3 & 16V?

Y Synthesiser OK. A No VCO RF output. N N 9V present at VCO Q4/Q5?

Y DC V present at Q4 & Q5?

Y 8.3V present at VCO?

N Y Check Tx reg., Q610 & 9V reg. Check biasing resistors, Q4 & Q5. Check Q5 C multiplier

(synth). DC V present at VCO, Q1, Q2 & Q3?

N Check biasing resistors, Q1, Q2 & Q3. Y Capacitors OK?

Check for cracks, shorts, etc. N Replace if faulty. Y Replace VCO. Check VCO tuning caps & trimmer. N VCO trimmer freq. range OK?

Y Check #C1, #C7, #C8, C6 & D1-D2 in VCO. N Is 8MHz VCO range achieved between 3 & 16V?

Y VCO OK. Continued on the next page N N 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.13 B Continued from previous page Check microcontroller section (IC810). Replace synthesiser

(IC740). Y Is reference clock present at IC740 pin 20

(200kHz >4.5Vpp)?

N Y Is reference clock present at IC730 pin 12

(200kHz >4.5Vpp)?

N Y Is reference clock present at IC730 pin 1

(12.8MHz >4.0Vpp)?

N Check TCXO (IC700) and buffers (IC710). Check phase detector output pins (IC740 pins 3 & 4). Are there very narrow pulses

(~50ns) at the reference frequency?

N

(i.e. 5kHz : 200s period 6.25kHz : 160s period)

*See Note below. Y Is the charge pump bias voltage at the base of Q760 & Q780 between 3.5 and 5V? (5V when locked) N Y Is the voltage on C762, R760, and R758 9V 0.2V?

N Y Is the charge pump voltage on Q790 gate between 3 and 8.5V? (6.5V 0.2V locked) Y Is the loop filter reference voltage at C772 (+) 6.5V 0.2V?

Y N N Check loop filter components R775, C774, C776, R510, C505, IC750. Is the supply to IC750 +20V +4, -2V?

N Y Check programming. Check serial bus when programming i.e. clock/data/enable activity (IC740 pins 18, 19 & 17). Check Q760, Q780, R766 & C765. N Programming and serial bus OK?

Y Check phase modulator sections:

IC720, Q710, Q720, D710, Q730, Q740, D720. Check R762 & C762. Check divider IC730. Check charge pump components

(Q775 & Q780) and Q790. Check C772, R774, R772, C770, R763 & Q790. Check regulator circuitry. Check the signal path from the VCO to synthesiser. Measure the frequency from the VCO at IC740 pin 11 using No signal Check VCO. a frequency counter. Signal Is the level >-10dBm?

Does the frequency adjust as the VCO trimmer is adjusted (out of lock)?

N Check divider buffer circuit (Q795) and bias voltages on Q795 emitter

(1.3V 0.2V). Y Replace synthesiser

(IC740).

*Note:

When locked, both of these are very narrow (~50ns). If unlocked, one will be very narrow (~50ns), and the other wide (>15s). Copyright TEL 31/09/98 C5.14 T856/857 Fault Finding M850-00 C Noisy synth;

poor residual FM. VCO phase locked?

3-16V present on control line?

N Y Correct DC V present on Q1 VCO?

Y Loop filter &

components around op. amp. (IC750) OK?

Y Isolate audio modulation on VCO;

still noisy?

N N N Go to B. Check inductors, biasing resistors

& Q1. Replace if faulty. Trace audio fault. Y Change trimmer;

still noisy?

N Y Change Q1;

still noisy?

N Y Change TCXO;

still noisy?

N Y Change varactors;

still noisy?

N Y Replace VCO assembly. Y Synthesiser OK. 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.15 5.7.4 T856 Drive Amplifier Key exciter

& lock synthesiser. 10.5V on Q350 collector?

10.5V on Q355 collector?

Y N 10.5V on Q315 collector?

N Y Check continuity of power rails

& DC paths to Q365 & Q370. 11.5V on IC350 pin 7?

N Y 13.8V on IC350 pin 8?

Check VCO. Check regulators. N Check 9V &

13.8V supplies. Check lock det. path back to synth. IC740, IC750, Q325. Check temp. shutdown circuit. N N Y Check TP305

>+8V. Y Check TP320

<0.6V. Y Check Q310, Q315 circuitry

& IC350. Check attenuator pad #R517, #R518,

#R519. Check C355, C358, C360, Q350, D340, D380, D360, L320. Check Q350. Check signal path between Q350 & Q355. Check Q355.

>2V RF at VCO output?

N Y N

>1V RF at R381?

Y

>0.5V RF at Q350 base?

N Y

>5V RF at C362, #R395?

N Y

>1V RF at Q355 base?

N Y

>6V RF at Q355 collector?

N Y Check signal path to output incl. output socket (SK310). Copyright TEL 31/09/98 C5.16 T856/857 Fault Finding M850-00 5.7.5 T856 PA & Power Control Set RV320

(power adjust) fully clockwise;

synth. locked;

key Tx. Normal operating conditions:

Forward power = 4.7V approx. Reverse power

= 0.7V approx.

= 2.02V IC350 pin 6

= 2V IC350 pin 5 IC350 pin 7

= 8.63V Check Q410, Q420 & circuitry, LP filter. Tx delivering full power

(>30W)?

N Y Y 10.8V at L310?

N Check drive at SK310 >1.5W. Y N Y Check +13.8V at Q410 & Q420. N Refer to Drive Amp. Fault Finding Chart. Check supply circuitry.

<2V on IC350 pin 6?

Y N Check IC330, Q310, Q315

& circuitry,

+13.8V supply. Check lock det. circuit;

TP305 should be >8V. Check temp. shutdown circuit (IC350);

TP320 should be <0.6V. Check Q320, RV330. Turn RV310 ccw. Check power drops to zero slowly in a controlled manner. N Does variation of RV310 cause either full power or no power?

Y Check for break in power sense circuitry; directional coupler D420, D440 & circuitry. Y Set RV310 so that output power = 25W;

check L310 approx. 7.5V. Momentarily remove Tx load. Voltage at L310 decreases to approx. 5V?

Y Power control circuitry OK. Note:

c/w = clockwise cc/w = counterclockwise or anticlockwise 31/09/98 Copyright TEL M850-00 T856/857 Fault Finding C5.17 5.7.6 T857 Exciter Drive Amplifier Check power rails. Check IC300. Key exciter &

lock synthesiser. 9V at Q304 collector?

0.5V at Q304 base?

9V at Q305 collector?

N Y N N

>2V RF at VCO output?

Y

>1V RF at R323?

Y

>0.5V RF at Q304 base?

N Y

>5V RF at

#C321, #R330?

Y

>1V RF at Q305 base?

N Y

>5V RF at Q305 collector?

Y Drive amp. OK. N N Y N 9V at Q303 collector?

N

>4V present on IC300 pin 1?

Y Check Q302

& Q303. Check VCO. Check attenuator pad R517, R518, R519. Check C314, #C315,

#C316, Q304, L305, D201, D202, D203. Check Q304. Check signal path between Q304 & Q305. Check Q305. Copyright TEL 31/09/98 C5.18 T856/857 Fault Finding M850-00 5.7.7 Audio Processor Key exciter &

lock synthesiser. Connect 1kHz audio to external CTCSS input. Does exciter modulate?

N Y Check alignment of modulators. Y Demodulated audio frequency response flat between 50 & 300Hz?

N N Audio frequency response IC260 pin 1 flat 300Hz to 2kHz?

Y Audio frequency response IC210 pin 8 6dB/octave slope?

N Y Check low pass filter stage IC260 pins 1, 2 & 3. Audio superimposed on 200kHz signal IC720 pins 9 & 3 (synth)?

Y Y Y Audio output at IC260 pin 8?

N Audio output at IC260 pin 1?

N Audio output at IC260 pin 7?

N Check stage IC260 pins 5, 6 & 7. Check audio path to VCO control line. Check buffer IC260 pins 8, 9 & 10. Check low pass filter stage IC260 pins 1, 2 & 3. Check integrator IC210 pins 8, 9, & 10. N Check audio path between integrator

& phase modulator. Y 200kHz clipped triangle wave at IC720 pins 8 & 4?

N Check IC720, Q710, Q720, Q730, Q740, D710, D720, C727, C729, C724 & C725 Y Check loop filter

(IC750, pins 5, 6 & 7)

& associated components. Select standard audio configuration. Connect audio to line input;

key exciter. Y Does exciter modulate?

N Demodulated audio frequency response as per Section 4.5?

N Check pre-emphasis network IC230 pins 12, 13 & 14 &/or low pass filter IC260 pins 1, 2 & 3. Y Audio processor OK. Y Y Y Y Audio signal at IC210 pin 14?

N Audio signal at IC230 pin 1?

N Audio signal at IC230 pin 14?

N Audio signal at IC240 pin 4?

N Y IC240 pin 6 at 9V?

N Check Q260 is not faulty or being turned on inadvertently. Check audio path between limiter IC210 pin 14 &

summing amp. IC260 pin 7. Check IC210 pins 12, 13 & 14. Check IC230 pins 1, 2 & 3 or audio path between pre-

emphasis network & limiter. Check IC230 pins 12, 13 & 14 or audio path between multiplexer

& pre-emphasis network. Check IC240 or audio path between line trans-

former & multiplexer. 31/09/98 Copyright TEL M850-00 5.8 Caution:

Caution:

T856/857 Fault Finding C5.19 To Replace The T856 PA Transistors

(Q410 & Q420) Failure to comply with the following procedure can result in failure of the device due to poor heatsinking, or worse, can endanger the health of the assembler if the beryllium oxide die carrier is smashed during assembly. As the location of certain components in the PA is critical to perform-

ance, it is important that any components removed or disturbed are refitted in exactly the same position. Before attempting to remove a transistor, measure the distance between the capacitors and transistor body to the nearest 0.5mm (meas-

urement "A" in Figure 5.2) so that the capacitors can be replaced in exactly the same position. These measurements are shown in Figure 5.2 for the 6LFL package, however the same procedure applies for the SOE (stud) package. Caution:

Do not apply too much heat or pressure to the PCB pads and tracks as you may damage them or lift them from the PCB, causing permanent damage to the transmitter. base collector measurement A Figure 5.2 Typical Transistor/Capacitor Spacing (Not To Scale) Desolder and remove the components from around the transistor. Q420 Only:

Desolder and remove the two solder tags. Desolder the transistor tabs by heating with a soldering iron and lifting away from the PCB with a screwdriver or thin stainless steel spike, then remove the device. Copyright TEL 31/09/98 C5.20 T856/857 Fault Finding M850-00 Q410 Only:

Unscrew the transistor stud nut and remove the device. Remove any excess solder from the PCB pads with solder wick. Trim the tabs of the replacement transistor so that the device sits neatly on the PCB pads provided. Lightly tin the underside of the transistor tabs. Remove any excess solder to leave a thin, even layer on the tabs. Apply a small amount of heatsink compound (Dow-Corning 340 or equivalent) to the transistor mounting surface. Sufficient compound should be used to ensure an even film over the entire mounting surface. Place the transistor on the PCB in the correct orientation and ensure the tabs are flush to the surface. Q410 Only:

Lightly solder one tab to the PCB, then torque down the retain-

ing nut to the correct torque (0.7Nm/6in.lbf.). Caution:

Do not solder all the tabs before torquing down otherwise the device may be broken. Q420 Only:

Refit the solder tags. Solder all transistor tabs to the PCB. Replace each component in exactly the same position as noted previously. 29/02/00 Copyright TEL M850-00 6 Caution:

T856/857 PCB Information T856/857 PCB Information C6.1.1 This equipment contains CMOS devices which are susceptible to damage from static charges. Refer to Section 1.2 in Part A for more information on anti-static procedures when handling these devices. This section provides the following information on the T856 transmitter and T857 exciter:

parts lists grid reference indexes mechanical assembly drawings PCB layouts test points & options connections drawings circuit diagrams. Section Title IPN 6.1 6.2 6.3 Introduction T856 Transmitter PCB T857 Exciter PCB 220-01397-01 220-01398-02 220-01398-04 Page 6.1.3 6.2.1 6.3.1 6.3.29 Copyright TEL 29/02/00 C6.1.2 T856/857 PCB Information M850-00 31/09/98 Copyright TEL M850-00 T856/857 PCB Information C6.1.3 6.1 Introduction Product Type Identification You can identify the transmitter or exciter type by checking the product code printed on a label on the rear of the chassis (product codes are explained in Section 1.3 in this Part of the manual, and Fig-

ure 1.1 in Part A shows typical labels). You can further verify the product type by checking the placement of an SMD resistor in the table that is screen printed onto the top side of the PCB, similar to the example drawn below. In this example, the resistor indicates that the product was built as a T856-10-XXXX. 856-30 856-35 856-

PRODUCT TYPE PRODUCT TYPE 856-10 856-13 856-15 856-20 856-23 856-25 Note:

The only function of this resistor is to indicate the product type. It has no effect on the circuitry or operation of the transmitter or exciter. PCB Identification All PCBs are identified by a unique 10 digit internal part number (IPN), e.g. 220-01390-02, which is screen printed onto the PCB (usually on the top side), as shown in the example below:

The last 2 digits of this number define the issue status, which starts at 00 and increments through 01, 02, 03, etc. as the PCB is updated. Some issue PCBs never reach full production status and are there-

fore not included in this manual. A letter following the 10 digit IPN has no relevance in identifying the PCB for service purposes. Note:

It is important that you identify which issue PCB you are working on so that you can refer to the appropriate set of PCB information. Copyright TEL 31/09/98 C6.1.4 T856/857 PCB Information M850-00 Parts Lists The 10 digit numbers (000-00000-00) in this Parts List are internal part numbers (IPNs). We can process your spare parts orders more efficiently and accurately if you quote the IPN and provide a brief description of the part. The components listed in this parts list are divided into two main types: those with a circuit refer-

ence (e.g. C2, D1, R121, etc.) and those without (miscellaneous and mechanical). Those with a circuit reference are grouped in alphabetical order and then in numerical order within each group. Each component entry comprises three or four columns, as shown below:

circuit reference -

lists components in alphanumeric order variant column -

indicates that this is a variant component which is fitted only to the product type listed description -

gives a brief description of the component Internal Part Number -

order the component by this number The miscellaneous and mechanical section lists the variant and common parts in IPN order. Parts List Amendments At the front of the parts list is the Parts List Amendments box (an example of which is shown below). This box contains a list of component changes which took place after the parts list and dia-

grams in this section were compiled. These changes (e.g. value changes, added/deleted compo-

nents, etc.) are listed by circuit reference in alphanumeric order and supersede the information given in the parts list or diagrams. Components without circuit references are listed in IPN order. The number in brackets at the end of each entry refers to the Tait internal Change Order document. IPN of new component Change Order number Parts List Amendments R306 Changed from 180W to 560W

(036-13560-00) to increase sensitivity (71003). circuit reference or IPN description of change 31/09/98 Copyright TEL M850-00 Variant Components T856/857 PCB Information C6.1.5 A variant component is one that has the same circuit reference but different value or specification in different product types. Where two products share the same PCB, the term variant is also used to describe components unplaced in one product. Variant components have a character prefix, such as

&, = or #, before the circuit reference (e.g. &R100). The table below explains the variant prefixes used in T800 Series II products:

If the variant prefix is. the component will.

change according to channel spacing change according to frequency stability change according to frequency range change or be placed/unplaced for special applications be unplaced in one product

(where two products share the same PCB) Grid Reference Index This section contains a component grid reference index to help you find components and labelled pads on the PCB layouts and circuit diagrams. This index lists the components and pads in alpha-

numeric order, along with the appropriate alphanumeric grid references, as shown below:

components listed in alphanumeric order PCB layout reference circuit diagram reference component location on the sheet sheet number component location on the layer layer number -

1 = top side layer 2 = bottom side layer Copyright TEL 29/02/00 C6.1.6 T856/857 PCB Information M850-00 Using CAD Circuit Diagrams Reading a CAD circuit diagram is similar to reading a road map, in that both have an alphanumeric border. The circuit diagrams in this manual use letters to represent the horizontal axis, and num-

bers for the vertical axis. These circuit diagram grid references are useful in following a circuit that is spread over two or more sheets. When a line representing part of the circuitry is discontinued, a reference will be given at the end of the line to indicate where the rest of the circuitry is located, as shown below. The first digit refers to the sheet number and the last two characters refer to the location on that sheet of the continuation of the circuit (e.g. 1R3). these grid references show where the circuit is continued DISCRIMINATOR 1R3 2R9 2R9 8A2 IF-SIG 4R4

%R338 100 C371 10U R339 100K C369 100P C301 4N7 R303 12 DS G L310 33U 31/09/98 Copyright TEL