Service Manual Part 1

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Close the PTT switch and monitor the transmit frequency with a frequency coun-
ter.
Adjust RV923 on the TCXO/Tx audio PCB for a channel frequency within ±100Hz
at ambient temperature.
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DC isolate the audio generator from TSP901 using a capacitor (10µF is sufficient).
Set the audio generator to 7kHz and inject the audio into the dual point modula-
tion input TSP901 on the TCXO/Tx audio PCB.
Close the PTT switch and select the lowest frequency channel.
Adjust the audio generator level to give a reading of ±5.2kHz deviation on the
modulation meter.
Remove any filters selected on the deviation or modulation meter which could
give erroneous readings.
Select the highest frequency channel and check that the deviation is ±4.8kHz.
If not, adjust the audio generator output level so that the average deviation of the
two channels is ±5kHz.
The difference in deviation between the two channels must be less than
±800Hz.
Select the lowest frequency channel, set the audio generator to 70Hz and inject
the audio at TSP901.
Adjust RV222 to give ±4.8kHz deviation on the modulation meter.
Select the highest frequency channel and check that the deviation is ±5.2kHz.
If not, adjust RV222 so that the average deviation of the two channels is ±5kHz.
The difference in deviation between the two channels must be less than
±400Hz.