Batboard

I have a UHF GM300 with no signal audio. Beeps are normal and can be controlled by volume control. The logic board is a HLN8074E. The mute gate Q551 is biased open. I can bridge Q551 with a capacitor and the audio and radio seem normal. The mute gate does not seem to be used as noise squelch. What is causing the problem? Would it be OK to solder in capacitor and use radio that way?

I have seen 800 MHz MaxTracs that won't pass audio unless you totally unsquelch the radio from the front panel. Also, trunking radios may never pass audio unless the proper protocol has been established.

Sometimes if the VCO is unlocked, due to being programmed out of band, the microprocessor won't unsquelch the audio circuitry. Also, if the reference oscillator is bad, not much else will work properly. This is a common problem on MaxTracs, which are similar to GM300s.

Bob M.

GM300 has good receiver sens and good transmitt. Receive audio is just gated off.