Peavey 260 PA/mixer: Noise!

DeadSpeaker · 27th December 2008, 03:51 PM

I have been fixing up this old PA head, and it is producing this terrible noise. It sounds kind of like a guitar cable has come unplugged from a guitar.

A few of the pots had been broken off and all were disgustingly scratchy. I replaced the pots with miniature pots and used wire to connect them to the PCB. Each wire is about 1.5 inches long and there are 60 of them.

Could all that wire cause this noise?

Iain McNeill · 27th December 2008, 04:45 PM

so it's like a mains hum/buzz noise rather than a hiss noise?

Usually a sign of a ground problem. I think you're going to have to map out what's going on with ground and try and find the missing link.

Have you removed everything from the chassis?

Did you re-wire the power supply at all?

edit: 1.5" isn't too long per se, but it's more to do with loops. Twist or plaid the wires together to minimize inductive loop area. But I don't think this is your problem.

DeadSpeaker · 27th December 2008, 06:17 PM

Ground! That was it. The pots ground the PCB to the chassis. When I switched the pots out, I didn't realized the PCB was not connected to ground anymore. I simply soldered a wire from ground to the shell of a pot and now there is not more noise. Thanks for the help.

27th December 2008, 03:51 PM	#1
DeadSpeaker diyAudio Member Join Date: Jul 2007	Peavey 260 PA/mixer: Noise! I have been fixing up this old PA head, and it is producing this terrible noise. It sounds kind of like a guitar cable has come unplugged from a guitar. A few of the pots had been broken off and all were disgustingly scratchy. I replaced the pots with miniature pots and used wire to connect them to the PCB. Each wire is about 1.5 inches long and there are 60 of them. Could all that wire cause this noise?

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27th December 2008, 04:45 PM	#2
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	so it's like a mains hum/buzz noise rather than a hiss noise? Usually a sign of a ground problem. I think you're going to have to map out what's going on with ground and try and find the missing link. Have you removed everything from the chassis? Did you re-wire the power supply at all? edit: 1.5" isn't too long per se, but it's more to do with loops. Twist or plaid the wires together to minimize inductive loop area. But I don't think this is your problem.

27th December 2008, 06:17 PM	#3
DeadSpeaker diyAudio Member Join Date: Jul 2007	Ground! That was it. The pots ground the PCB to the chassis. When I switched the pots out, I didn't realized the PCB was not connected to ground anymore. I simply soldered a wire from ground to the shell of a pot and now there is not more noise. Thanks for the help.

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