Batboard

There seem to be an audio problem with my GM300. It appears to be a low volume scratching noise and sometimes relatively loud crackling noise. The noise problem is intermittent but the strange thing is if I apply 10V to the power supply, the problem disappears. As soon as I hit 11V or more, the noise is back (intermittent again). All this is happening without RX audio.

I have pin 15 and 16 of the accessory port shorted but removing the jumper does not remove the noise.

Can anyone pin point me to where I should start? Thanks.

Well, you could search this board for "GM300 problem", but since the search function doesn't work right, that probably won't help you, and I wouldn't want to look through thousands of useless results.

One very common problem with GM300s is the interconnect pins between the logic board and the RF board get corroded. This causes all sorts of noise problems, as well as the radio appearing to be way off frequency. This is the first thing to tackle. Remove both boards, clean all of the pins, and reassemble. That might fix things up.

If not, you've probably got a problem with a power supply capacitor or the audio power amplifier. An oscilloscope should help find what area is generating the noise.

Bob M.

Thanks for the info. I'll give that a try and see how it goes. Cheers~