2970 low Rx audio

[9wire]

Tx is good, signal appears to be good, the audio out of the speaker is low. Rf gain all the way up, volume all the way up, it's just not very loud. All modes, tried different speakers, both in the mobile and in the house. Any ideas?

 

[999]

Old school or DX?

 

[999]

Old school I'd start with these two caps.

 

[9wire]

It's a first gen.

 

[nomadradio]

Far too used to just probing pin 9 with a 'scope to see that the DC voltage is roughly half the power-supply voltage. If not, the audio chip is suspect. If the audio waveform looks okay, the problem is downstream from pin 9. If the audio waveform is weak I'll want to see if there is any significant audio voltage on pin 2 or pin 5, C219 or C216 could cause this. They are decoupling caps and should have little if any signal voltage on them. Holding the lead wires of a good cap up to the solder pads for either of those will settle that question. If the volume jumps up when the new cap's leads touch the solder pads, you know that one has failed.

73

 

[9wire]

Had some kind of mod done to it.