(b)
Amplifier Stages
Using a 10,7 MHz Marker Oscillator, obtain zero beat.
Remove channel crystal and Squelch IF Module (6).
Remove RF Amplifier Module (1) and fit appropriate Test (Extenstion) Assembly to it.
Plug the combined assembly into the Mother Board.
At the Mother Board pins vacated by Module (6), connect 4,5V battery to pin 2 (—ve)
and pin 3 (+ve).
Set Signal Generator to 5 mV PD and switch off modulation.
On the underside of RF Amp board locate track between L7 tap and TF3 pin 3 and
with the EVM probe in this position, tune L7 for maximum reading.
Check that reading is 50 mV RMS.
NOTE: L7 core will be at the end of its traverse at this point and it may not be
possible to obtain a peak reading. Ensure that the core does not run
out of thread.
Remove extension assembly.
Refit Module (1) to Mother Board.
Refit channel crystal.
(c)
Mixer Stages and 10,7 MHz Filter
Carry out operation (a) above (Preliminary Check) re-tuning L7, L8 for 1,0V DC
at 2TP1.
Set signal generator level to 1,5 mV PD.
Check that the reading at pin 1 of IF Module (2) is 50 mV RMS or greater.
At pin 3 of IF Module (2), check that reading is at least 5 db greater than that at pin 1.
5.
IF Amplifier Module (2) Noise Limiter and AF Filter (3)
Remove 10,7 MHz Crystal Filter by unfastening the two M3 nuts on the underside of Mother
Board.
Remove 4,5V battery and refit Squelch IF Module (6).
Set signal generator frequency to 10,7 MHz, level to 15pV PD modulated 30% at 1 kHz.
Connect signal generator to pin 1 (live) and pin 2 (—ve) of IF Module 2. (Underside of
Mother Board)
Set 2RV1 to maximum.
Switch off carrier and check that reading at 2TP1 is OV DC. If not, adjust 2RV1 anti-
clockwise so that the reading at 2TP1 just falls to zero.
Switch on carrier and check that reading at 2TP1 is 1V DC.
Using the EVM check that the audio output at pin 8 of Module (2) is equal to or greater
than 250 mV RMS.
At pin 4 of the Noise Limiter and AF Filter Module (3), check that the reading is 80 mV
RMS (EVM).
Remove Signal Generator from pins 1 and 2 of IF. Module (2). Refit the 10,7 MHz Crystal
Filter.
6.
Audio Amplifier (4)
Connect Audio Output Meter to Loudspeaker socket.
Remove Noise Limiter and AF Filter Unit (3).
Set Audio Oscillator level to 40 mV PD at 1 kHz.
Turn VOLUME control fully clockwise.
At the Mother Board pins vacated by Module (3) connect Audio Oscillator to pin 4 (live)
and pin 2 (—ve).
Check that the reading on the Audio Output Meter is equal to or greater than 1W into a
3S/ load.
4.17
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