Ampeg BA115HP Output and crackling/static

[Jazz P Bass]

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)."

[ca7922303]

Could incorrect voltages on Q6 have anything to do with it? Q6 is last part replaced that is reading incorrect?

[ca7922303]

I don't know here either.
If it is 0, then there is no +50V voltage.

Correction:
R34(+61/+61vdc) not using Variac.

Forgot that I can't get a good ground on the chassis. Have to use the speaker jack ground to get correct readings.

[g1]

Recheck voltages at U5 pins 4 and 8.
Check for signal at line out XLR.

[ca7922303]

Recheck voltages at U5 pins 4 and 8.
Check for signal at line out XLR.

U5 pin 4(-6mvdc)
U5 pin 8(16.6vdc)
No signal @ line out XLR

[x-pro]

Learn to think and repair.
Open the datasheet for U5 and determine what should be on pin 4.

[ca7922303]

Learn to think and repair.
Open the datasheet for U5 and determine what should be on pin 4.

(-16.6vdc)

[g1]

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.

[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.

Pin 4 is (-6.0 mvdc)
can check R9/R66 this evening after work.

[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.

R9(+17/+60vdc)
R66(-15mvdc/-60vdc)

[x-pro]

R9(+17/+60vdc)
R66(-15mvdc/-60vdc)

I don't get it.
Are you guys smoking colitas?

Why is there no (-16V) after R66?

[x-pro]

A few posts ago (-16V) were in place.
Is there a break in the soldering, in resistor R66, shorted D12 or C40, or somewhere else on the PCB?

[g1]

R9(+17/+60vdc)
R66(-15mvdc/-60vdc)

R9 should be negative voltages, re-check.

Take extra care when measuring, and when typing. Too many errors.

[nosaj]

R9 should be negative voltages, re-check.
R66 -60V is impossible, re-check.
Take extra care when measuring, and when typing. Too many errors.

Does anyone have any idea what point he is actually using for the black lead? I have had to learn myself that different points on an amplifier can give me different results.
nosaj

[g1]

Check value of R66 and check diode D12 with diode test.