Ampeg BA115HP Output and crackling/static

[ca7922303]

Have output and crackle/static thru speaker output. No crackle thru headphone output but seems to be reduced volume.

[x-pro]

Remove the amplifier board and check the soldering quality of the components.

[ca7922303]

Removed board, solder joints appear good. Reinstalled board, U1 thru U5 (+17/-17vdc).

[Jon Snell]

I would check AP1 for a dirty wiper, set the quiescent current, with no signal or load, to 15mA.
Check for noise, if still present, check TP12 for noise, if present on TP12, the issue is on or before that point, remove C11 and test again. If still present, replace U5 to test again. If gone suspect C11 leaking.
If still there, it could be Q9 or a drive transistor that is noisy. A tin of freezer is very useful in this case.

[ca7922303]

Removed one leg of C11 and no signal. Reconnected C11 and same as before, output with crackling distortion.

[g1]

When C11 was disconnected, was the crackling/static noise still there at the output?

[ca7922303]

No, no output at all, crackling included, with one leg up on C11.

[g1]

In post #4, Jon suggested that if lifting C11 got rid of the noise, it could be bad. Try replacing it.

[ca7922303]

In post #4, Jon suggested that if lifting C11 got rid of the noise, it could be bad. Try replacing it.

C11 is a (10uF 35v). Any problem I use a (10uF 50v) cap I have extra?

[DrGonz78]

C11 is a (10uF 35v). Any problem I use a (10uF 50v) cap I have extra?

Yes no problem at all.

[ca7922303]

In post #4, Jon suggested that if lifting C11 got rid of the noise, it could be bad. Try replacing it.

Replaced C11 with a 10uF 50v and no change with signal (mp3).

[x-pro]

What does mp3 signal mean?

[DrGonz78]

What does mp3 signal mean?

Probably just a line level signal output from some device. Probably fluctuating between 100-500mv.

[ca7922303]

What does mp3 signal mean?

Signal is my phone playing an audio file.

[g1]

Try shorting D to S pins of Q9 together