Busted XR-1200? Wrong forum category

[Novo]

Busted XR-1200?
I have an XR-1200 that has developed a waterfall (lacking better descriptors) sound when I run A and B up. The more the mains are up channels are up the louder the sound. The amps run fine plugged in directly...bypassing the mixer and the eq. I re-did the voltage regulators (on the main board) and a diode about two years ago.

I need it working or I need it out of the shop...

Thank you,


Novo

P.S. Peavey said clean the input/output switching jacks...did that. Also tried unplugging connections between them and the main board....no luck.

[Enzo]

OK, so the power amps are clean and you have a noisy mixer.

Isolate the problem. Noise increases as master goes up. OK does it do it with ALL the channel faders at zero? If not, then the master is clean. If it is still noisy, then the master is noisy, and since A and B are affected, we look for something they share, like an IC.


If the channel faders have to be up, then we have a noisy channel or channels. Bring the channels up one at a time, then back down all up the row. Are they all equally noisy, or do one or two stand out as noisy. If we have a noisy channel, then it makes sense that the master would also turn the noise up and down.


On low voltage stuff like this, noisy is almost always from a semiconductor, in this case on op amp IC.