Ampeg BA115HP Output and crackling/static

[g1]

Not able to read the photo. Can you upload a better copy? Thanks.

see post #74

[ca7922303]

see post #74

So, is he saying to inject a signal thru the (+ )end of (C11) this time instead of a cap connected to (R25) as I did previously along with (OC-1) and (C12) removed and nothing jumped?

[g1]

Q6 and C12 removed. OC1 disconnected or removed. Q9 jumpered from D to S.
C11 + end disconnected from circuit and signal going into + end of C11.

[ca7922303]

Q6 and C12 removed. OC1 disconnected or removed. Q9 jumpered from D to S.
C11 + end disconnected from circuit and signal going into + end of C11.

As referenced above:
TP12(0.0vac)
Set up like previously with a cap leg in R25, signal thru (+) end of cap:
TP12(1.03vac)
No signal thru headphone jack either way.

[g1]

C11 (-) end is connected to R25. If you lift it's + end and put signal there, it should do the same as connecting an external cap to R25.

[ca7922303]

C11 (-) end is connected to R25. If you lift it's + end and put signal there, it should do the same as connecting an external cap to R25.

Problem was I didn't lift a leg. Connected to the (+) end soldered in place, but since I went the previous way, do you have the measurements you need or lift a leg?

[g1]

Lift the + of C11 put the signal in there. It will verify that C11 is still good.
Also, whenever you are applying signal, you have to set the signal source level when it is attached to the circuit and adjust back to the specified level. If you set the level disconnected, it will change when you connect, and give errors in the results expected down the line.

[ca7922303]

Lift the + of C11 put the signal in there. It will verify that C11 is still good.
Also, whenever you are applying signal, you have to set the signal source level when it is attached to the circuit and adjust back to the specified level. If you set the level disconnected, it will change when you connect, and give errors in the results expected down the line.

Setup as described:
TP12(1.3vac)

[x-pro]

What is the AC voltage at TP10 and TP11?

[ca7922303]

What is the AC voltage at TP10 and TP11?

@(109vac Variac)R31(50vdc)
TP10(2.45vac)
TP11(53vac)

[x-pro]

So it's working.
Now disconnect +C11 from the alternator and reinstall it. Make sure that +C11 is connected to pin 1 of U3:A. Apply a 700 mV sine wave to input J1 or J2. Make sure it is present at TP11. Do not connect the speaker yet.

[ca7922303]

So it's working.
Now disconnect +C11 from the alternator and reinstall it. Make sure that +C11 is connected to pin 1 of U3:A. Apply a 700 mV sine wave to input J1 or J2. Make sure it is present at TP11. Do not connect the speaker yet.

C11 reconnected and (+) pin is connected to U3:A pin 1.
TP11(45vac)
700mv sine wave to J1 (108vac Variac)R31(50vdc)

[x-pro]

Now solder in place of OC1
and check the output again.
If all is well, replace the previously removed parts one by one. Field effect transistors too.

[ca7922303]

Now solder in place of OC1
and check the output again.
If all is well, replace the previously removed parts one by one. Field effect transistors too.

What readings to check after resoldering OC1 or am I checking for speaker output?

[x-pro]

Output TP11.
If there is no DC voltage at the amplifier output (TP11) or it is mV, you can connect a speaker. Hopefully it is in good working condition.
Keep an eye on the volume level. Otherwise you will go deaf.