jvm 6/11/2018 1:02 PM
Peavey Special 130 white noise/hiss
I have a Peavey Special 130 with excessive white noise/ hiss. It is present in both channels, channel switching is working fine, power supply voltages are normal. The amp works fine other than this hiss. The saturation control increases the noise even when the clean channel is selected. I have subbed U1, U2 and U3 with no change in the noise level. Anyone familiar with this noise issue in Solo series Peaveys? [ATTACH]49247[/ATTACH]
 
Enzo 6/11/2018 3:00 PM
ANy amp, any model, any brand, can come up with a noisy stage somewhere. Nothing particular about thos amp.

Isolate the problem. Does the post control turn the noise up and down in either channel? Other than saturation, do ANY of the other controls affect the noise in ANY way? (tone, volume)

Your ICs are in sockets aren't they? Pull U3, noise stop? Put it back, likewise pull U1 and U2 one at a time to see if either kills the noise. You replaced them, but we need to see which circuit area is involved.

And don't forget U4, try pulling it as well.

Plug the guitar into the power amp IN jack and dial it to zero. Hiss gone?
 
jvm 6/11/2018 3:39 PM
Hi, Enzo. Thanks for your help! The post control does increase the noise level in with either channel selected as do the tone controls. I pulled all four op amps one at a time. Pulling U4 had no affect on the noise. U1,2,3 each stopped the noise when pulled individually. I plugged in to the power amp in, guitar volume off, no noise.
 
jvm 6/12/2018 8:45 AM
Since pulling U1 stopped the noise I used my audio tracer and found noise at Pin 7 of U1. No noise at pin1. U1B circuit resistors all within spec. Is clipping new caps across the existing caps a viable testing procedure here?
 
Enzo 6/12/2018 9:34 AM
I am more inclined to suspect CR3,4.
 
jvm 6/12/2018 11:44 AM
I replaced CR3 and 4. No improvement. Still white noise at pin 7