JCM 900 with loud channel switching pop.

[ahamay79]

I just had a customer call saying his 100 watt JCM 900 head is making a loud pop ("power surge" as he called it) when he switches channels. It didn't do it after I did a cap job and a re-tube on it a month or so ago. It was switching nice and quietly even at full volume. He said it's a really loud pop when he's using a distortion pedal with the amp.

Plus this model has the 5881/6L6's from the factory. Anything else I need besides a new PT and a little re-wiring to convert it to EL34's?

Thanks,

Dave

[ahamay79]

I also found out that he's running everything through the effects loop. Since I've never run a distortion pedal through an effects loop.... since I don't own any amps with effects loops, could that be a problem, or the problem?

Thanks,

Dave

[ahamay79]

Any takers?

[pontiacpete]

I subscribed to this thread cause I'm waiting to see if it is what you asked, is it that he's running everything through the effects loop.
standing by...
pete

[ahamay79]

Do you have one doing it too?

[pontiacpete]

No, I do have JCM 2000, but that didn't do what your talking about. I'm reading this thread to learn. It's an interesting problem. If I were in your position I would have him plug straight in and try changing channels and see it the popping occurs. Then take it from there.

pete

[ahamay79]

Oh yeah. I want him to bring the head in and hook it up exactly like he does at home so I can see what he's doing.