Tait T850 II Series, Service Manual

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C5.6 T856/857 Fault Finding
M850-00
31/09/98 Copyright TEL
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.