Ampeg BA115HP Output and crackling/static

[ca7922303]

And what is the voltage now on D12 (set in place) when power is applied to the amp?

Check D12 voltage with C40 removed?

[x-pro]

yes

[ca7922303]

And what is the voltage now on D12 (set in place) when power is applied to the amp?

With ground @ speaker output:
D12(-16/-16vdc)

[x-pro]

Hallelujah.
Check other voltages at the reference points

[ca7922303]

R66(304 ohms)
D12(0.0 v) diode test

R66(-76/-16vdc)

[ca7922303]

How's that? If on Q1 b(-3V), why is AP1 1V on all pins.

Q1-B(-15vdc)
AP1(-15/-15/-15)

[ca7922303]

13 pages of posts!

"Why is there almost zero on pin 4 of U5?"

Page 1/ post 3 he had it. " U1 thru U5 (+17/-17vdc)."

U5-Pin 4(-16vdc)

[ca7922303]

So you have -0.06V at pin 4 of U5 but it should be -16V.
Look at the partial schematic in post #183. One side of R66 should be around -50V, the other side -16V. R9 should have around -16V on both ends.

R66(-16/-77vdc)
R9(+17/+61vdc)

[x-pro]

R9(+17/+61vdc)

Look at the schematic carefully and the quote you provided!!!

[g1]

Look at the schematic carefully and the quote you provided!!!

I noticed that before. The voltages he listed seem to be for R68 rather than R9 on schematic. Maybe the labels on the board do not match the schematic.

[g1]

Check pin 4 voltage at U1 or U2.

[ca7922303]

I noticed that before. The voltages he listed seem to be for R68 rather than R9 on schematic. Maybe the labels on the board do not match the schematic.

Correction:R9(-5mvdc/+0.6vdc)
Thought R9 was a cement resistor that I couldn't read numbers on board till I checked schematic.

[ca7922303]

Check pin 4 voltage at U1 or U2.

U1 Pin 4(+0.6 vdc)
U2 Pin 4(+0.6vdc)

[g1]

One end of R9 should connect to the end of R66 that has -16V. Find out why it is not connected.

[ca7922303]

One end of R9 should connect to the end of R66 that has -16V. Find out why it is not connected.

So negative end of R9 goes to J28(0.0 ohms)
J28 to J29(0.0 ohms)
J29 to R66(0.0 ohms)
R9(-16/-16vdc)
Must been the connector not on good.
Reinstall C40?