help ME!! amp tech question..

[a7x_rox_12]

hello,

i play a peavey xxx head, and today during band practice the amp's sound would start fading away until the amp wasnt making any noise, but the amp was still on and the tubes were still glowing. it would then start working again a few minutes later, only to die out again soon after. now its not making any noise at all, but everything appears to be working. what in the world is going on? please tell me its a simple fix, or else im out 500 dollars :/

 

[glassman]

Re: help ME!! amp tech question..

Describe the tonal character as the amp faded out...and again as it faded back in. A reference from a cleanish tone would be helpful.

 

[a7x_rox_12]

Re: help ME!! amp tech question..

well, it was on the ultra channel, so no clean-ness whatsoever. is that what you meant?

but it faded out as if you turned off the standby, but took a bit longer; about 5 seconds of decreasing volume until it was completely quiet.

as for it coming back, it was like it wasnt ever broken and just turned on again

 

[glassman]

Re: help ME!! amp tech question..

I gotta log off for the day...but if you could get it to fade out while in clean mode and report back, I may be able to give you some direction.

It could be as simple as an intermittent heater on one of the preamp tubes (Peavey uses frequently uses 24VDC and series wires 4 tube's heaters together) or just a poor connection on an individual tube. The fading out and back in leads me to suspect this. Component failures are usually more abrupt and/or have other sounds that accompany.

Another possibility is a mains fuse that has a loose filiment...this is inside the amp and I don't recommend you tackle this yourself as some are buried under multi-layered boards in some Peavey equipment.

 

[a7x_rox_12]

Re: help ME!! amp tech question..

i cant even get a sound out of it anymore.
i'll take it to gc and see if they can diagnose somethin

 

[zzmoore]

Re: help ME!! amp tech question..

I gotta log off for the day...but if you could get it to fade out while in clean mode and report back, I may be able to give you some direction.

It could be as simple as an intermittent heater on one of the preamp tubes (Peavey uses frequently uses 24VDC and series wires 4 tube's heaters together) or just a poor connection on an individual tube. The fading out and back in leads me to suspect this. Component failures are usually more abrupt and/or have other sounds that accompany.

Another possibility is a mains fuse that has a loose filiment...this is inside the amp and I don't recommend you tackle this yourself as some are buried under multi-layered boards in some Peavey equipment.

It could be a lot of things, but "glassman" makes a pretty good guess with the DC heaters. I have had very similar problems with The JCM 2000's. It happens after heat up, and while you are playing. SS rectifier failures, or even partial failures. Keep in mind, your preamp tubes are dual triodes. They can look OK, and only have half the tube working. Kind of tricky stuff, not to mention frustrating. Don't be afraid to try a new set of pres.
Like I say (if my opinion means anything) glassman is speaking wisdom. Maybe check back with him if the store is no help to you.
Good Luck

 

[James Rock]

Re: help ME!! amp tech question..

I always say by new tubes before spending money on a tech looking at it. As you'll always be able to use the tubes (unless u suddenly) and most problems are tube related.