SERIOUS white noise!

[anoxmusic]

Alllllrighty.... yay! problems! here's the deal: I have a rack consisting of 3 A12's, 3 N72's, and finishing it off with 2 J99's. J99 #1 works perfectly. J99 #2... extreme white noise. So.... now we trouble-shoot: rechecked the voltages: perfect, took out the op-amps: no white noise - no sound obviously, but no white noise, took out the other op-amps from the working J99 and put them in non-working J99: still white noise, put original op amps from non-working J99 into working J99: works perfectly. OK... conclusion #1: op amps not the problem. Put only U2 in non-working J99: still white noise. Took out U2 and put op amp in only U1: no white noise. OK.... conslusion #2: something in circuit with U2 is fucked up. Took out non-working J99. Checked and double checked and triple checked my work. Everything looks groovy, voltages are where they're supposed to be on U1, U2, U3 and holding steady. Argh! Now here's where it gets hairy: during the last step of biasing after you adjust the voltages for the op amps and insert them into U1 and U2 and then you're supposed to check pins 4 and 6 on U2 to make sure that your voltage drops below 5mV... wellllll..... I sort of slipped with my test lead and briefly connected pins 4 and 5 creating some sparks! WEEE! What fun! I thought for sure I blew the op amps, but no. They're fine. Looks like I blew something else instead.... Tim, is this beyond my repair? Should I send it back to you? Anyone else with some thoughts, opinions, or condolences?

Ugh...,
~Joe

[tpryan]

What's the status on this one? After shorting pins 4 and 5, all the test voltages are OK? What happens if you lift one end of R24? Does that affect the noise? Let us know what you find.

[anoxmusic]

Well, the status is still: unworking. I was able to track a cool noise tune with it though, a la Merzbow, listen if you dare. And yes, that's correct, I shorted pins 4 and 5 and all the voltages are fine. Forgive me, but I don't know how to go about "lifting" one end of that resistor. Does that mean just unsoldering one end of it and pulling it out of the hole? Help?

Thanks,
~Joe

[tpryan]

Does that mean just unsoldering one end of it and pulling it out of the hole?

Yes. Is the noise present at every gain setting? Are you absolutely sure you have the small ceramic capacitors in the right locations? Have you inspected your solder joints very carefully?