Ampeg BA115HP Output and crackling/static

[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.

With OC-1 reinstalled:
TP11(-45mvdc)
No speaker output
Headphone only.

[g1]

The OC1 should have 2 leads on each side. If one side is labelled 'LED', measure DC volts between the 2 leads on that side.

[ca7922303]

The OC1 should have 2 leads on each side. If one side is labelled 'LED', measure DC volts between the 2 leads on that side.

Unable to see LED anywhere on OC1, but measured dc volts across both sets of leads.
Leads facing back of chassis(-308mvdc)
Leads facing front of chassis(-0.3 mvdc) but am able to hear some radio interference thru speaker output.

[g1]

Double check those OC1 DC readings while applying signal (same conditions that gave you 45VAC at TP11 before).

[ca7922303]

Double check those OC1 DC readings while applying signal (same conditions that gave you 45VAC at TP11 before).

With 1000hz/.70v sine signal thru front input, getting exact same results @ OC1.
Can hear signal from generator, but not thru speaker output and headphones are not connected. Not sure how I'm able to hear it. Can hear radio interference thru speaker only.

[x-pro]

Check R8, R7, R4, R6, D2, D3, D4, D5. LED OC1(leads pointing to the rear).
Connect the leads to the front side in ohmmeter mode when the unit is switched off.

[ca7922303]

Check R8, R7, R4, R6, D2, D3, D4, D5. LED OC1(leads pointing to the rear).
Connect the leads to the front side in ohmmeter mode when the unit is switched off.

R8(+53/+44vdc)
R7(+44vdc/0mv)
R4(-53/-44vdc)
R6(-44vdc/0mv)
D2(+44vdc)+180mvdc)
D3(-43/+180mvdc)
D4(-116mvdc/-44vdc)
D5(-132/-42mvdc)
OC1-rear(+177/-124mvdc)
OC1-front(46k ohms)

[x-pro]

That doesn't make any sense.
Where is the voltage at the anode, where is the voltage at the cathode? Total mismatch of voltages on D3, D5 with voltages on D2, D4.
and again +/-53 V !
it is necessary to learn how to correctly measure the voltage on the diode and LED

[x-pro]

Without optocoupler OC1, without capacitor C12, without transistor Q6, you have normal output voltage in TP11 when the input signal is sinusoidal.
As soon as you put OC1 in, did the output voltage disappear?

[ca7922303]

Without optocoupler OC1, without capacitor C12, without transistor Q6, you have normal output voltage in TP11 when the input signal is sinusoidal.
As soon as you put OC1 in, did the output voltage disappear?

I'm thinking I may have forgot the jumper wire after removing/reinstalling board again to solder OC1. I'll check when I get off work this afternoon.

[ca7922303]

Without optocoupler OC1, without capacitor C12, without transistor Q6, you have normal output voltage in TP11 when the input signal is sinusoidal.
As soon as you put OC1 in, did the output voltage disappear?

So, that's what it was. Forgot to jump Q9-S to D. Now have speaker output. So reinstalling Q6 and C12 does what? And is there any issue running without Variac @ (120vac) and R31 @ (60vdc)?

[x-pro]

If the OC1 node fails, there may be a problem when more than +/-50 VDC is applied to the amplifier.
C12 may be shorted at its terminals.
If Q6 is serviceable, it will not interfere with operation. Q9 needs to be put in place as well.

[x-pro]

After installing each part, check the signal output to the speaker.

[ca7922303]

After installing each part, check the signal output to the speaker.

Thanks for all the help. Will post as I'm reinstalling parts.

[ca7922303]

Need to replace the two(2) j112s(Q6/9). Broken pins. J112s expensive and slow to deliver on Amazon (have free shipping). Will 2n5457 work? Thanks.