Hi, I have a GM4200 which will not raise or lower the input gain when the gain pot is adjusted.
I have cleaned the gain pot, checked for dry solder joints and no change.
I tested the amp with both phono and din input, interestingly when I use a din input the amp plays louder but the audio is distorted unless I turn the source volume down.
Using din input has no affect on the gain pot either?
I have cleaned the gain pot, checked for dry solder joints and no change.
I tested the amp with both phono and din input, interestingly when I use a din input the amp plays louder but the audio is distorted unless I turn the source volume down.
Using din input has no affect on the gain pot either?
Is there anyway of testing the gain pot without removing it from the board, I have a feeling it's not the gain pot.
When the source vol is turned up the audio becomes distortedn, this amp should play clean even at full volume on low gain.
When the source vol is turned up the audio becomes distortedn, this amp should play clean even at full volume on low gain.
No the source is working fine Perry.
I just hooked it up to a Kenwood KAC923 and the audio was crystal clear and much louder even at very low gain.
I just hooked it up to a Kenwood KAC923 and the audio was crystal clear and much louder even at very low gain.
Thanks Perry, I assume I will need a scope to check the signal chain?
I don't have one at present.
I don't have one at present.
Have you checked the various points in the audio signal path for excessive DC?
Have you confirmed that the muting is releasing?
Have you confirmed that the muting is releasing?
How do I check the muting?
I did a quick experiment bypassing the input circuit and the amp plays as it should so maybe it is stuck in mute?
I did a quick experiment bypassing the input circuit and the amp plays as it should so maybe it is stuck in mute?
The voltage on the muting transistors (base to emitter) will be 0v to pass audio (no muting) and about 0.6v to shunt audio to ground (mute).
I can't make out the Q numbers on the schematic for the muting transistors Perry, can you check them for me please? might be clearer on your side.
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