Ampeg BA115HP (2003) humming

[g1]

There are lots of generator apps available for cel phones. Or just google up '400hz test tone' or whatever frequency you want, they're all up on youtube. You will need some kind of adapter cable to go from mini-headphone out to 1/4" plug.

It's not clear exactly what you are trying to fix right now, I'm guessing there are other issues aside from the mechanical hum/buzz of the transformer?
First thing is to disconnect speaker and make sure there is no DC on amp output.

[okw]

The mechanical hum/buzz is present, but there is also an electrical issue. I'm completely new to troubleshooting audio gear (have some experience with troubleshooting analog and digital circuits). My signal generator arrived. What amplitude (mV) do you recommend for the 400Hz test tone? If I have DC on the speaker, what would that indicate? And if I don't have DC, what is the next step?

[okw]

I've gone through the whole circuit now, and all voltage rails are ok, signal levels (test points) are more or less within the values from the service manual. Except this:
TP10 (NE5532 out2) should be 2.0VRMS, which is 10mV. I suspected the op-amp and replaced it, still 10mV. I measured in2- and it is also around 0V. Even though TP12 was 950mVRMS (should be 800mVRMS), which is connected with a 1k between them (and a lot of other stuff).
TP11 should be 26.3V, but i 31.6V.


Any help would be appreciated.