Ampeg BA115HP Output and crackling/static

[ca7922303]

Do you now have proper -16V across C40 ?

C40(-3.3/0.0vdc) tried four(4) different ground points, all read the same.

[g1]

C40(-3.3/0.0vdc) tried four(4) different ground points, all read the same.

Try the diode check on D12 again. If it reads good, proceed as in post #237, but instead of checking the resistance at C40, check the voltage. When it comes back to -16V, you should have located the bad IC.

[ca7922303]

Try the diode check on D12 again. If it reads good, proceed as in post #237, but instead of checking the resistance at C40, check the voltage. When it comes back to -16V, you should have located the bad IC.

D12(0.46 V) diode check in circuit

[g1]

That seems low. Lift one end and re-check.

[ca7922303]

That seems low. Lift one end and re-check.

D12(0.63V) diode test out of circuit.

[g1]

D12(0.63V) diode test out of circuit.

Does the diode check give 'OL' reading when you reverse the probes? If so, the diode should be ok. Go back to post #245.

[ca7922303]

Does the diode check give 'OL' reading when you reverse the probes? If so, the diode should be ok. Go back to post #245.

D12(17M)ohms with leads reversed out of circuit.

[ca7922303]

Does the diode check give 'OL' reading when you reverse the probes? If so, the diode should be ok. Go back to post #245.

Desoldered and made sure pin4 was not connected in circuit on U3/U4 and still not getting (-16v) at C40.

[g1]

Do the same with U1 and U2.

[ca7922303]

Tried same with U1/U2,
still getting(-3.3/0.0 vdc)@C40 four(4) different
ground points.

[g1]

Measure DC volts at both ends of R66 and at both ends of R9.

[ca7922303]

Measure DC volts at both ends of R66 and at both ends of R9.

R66(-61/-4.7vdc)
R9(-4.7/-4vdc)

[g1]

R66 still measures good and it's solder joints are good?
If so, you have almost double the current running through it than normal. Measure resistance across C40 again. I would suspect you have another solder bridge somewhere that should not be.
Pictures of both sides of the board might help.

[ca7922303]

R66 still measures good and it's solder joints are good?
If so, you have almost double the current running through it than normal. Measure resistance across C40 again. I would suspect you have another solder bridge somewhere that should not be.
Pictures of both sides of the board might help.

R66(320 ohms)
C40(2.9k ohms)
I'll remove the board again for photos under R66 shortly.

[ca7922303]

R66 still measures good and it's solder joints are good?
If so, you have almost double the current running through it than normal. Measure resistance across C40 again. I would suspect you have another solder bridge somewhere that should not be.
Pictures of both sides of the board might help.

Photos: