amp problem, please help

[hellrider77]

o.k. i started having problems with my peavey backstage plus 1x12. i have no idea about electrical work so i figured i would ask for some help.

when i turn it on, it barely produces any volume like it should, (on 3 it is enough to hear through the house) now i have to turn it up to around 6 or 7 just to hear it. i will play for a little while then it starts surging like it is trying to get louder,(think of using a volume pedal and shifting back and forth) then all of a sudden BOOM, it blows your ears out and plays normal and i turn it down. it will play like this for 30 minutes or so then fade out again and the volume starts surging again. before it started doing this, it started having a little distortion through the speaker like you were running a very mild overdrive. at first i thought maybe it was the speaker, but i took it out and tried it through another amp and it was fine, no distortion at all, so that also is coming from the amp. then tonight it starts this with the volume surges. i have no idea whats wrong. none of the pots are scratchy and neither isthe jack. it's just hell i dont know. some one please help and tell me what all could possibly be goin wrong here. this is my practice amp. i dont want to be relacated to the shop everytime i wanna jam because the crate is just way too loud to try and play in here.

 

[suislidE03]

Re: amp problem, please help

Well i was having the same problem with my laney, the tech said it was a bad micro chip that was causing the volume fades and jumps. I havent gotten it back yet, but thats the last thing they told me was going on.

 

[hellrider77]

Re: amp problem, please help

well, looks like its gonna cost some money then. i was hopin it might be a simple solution. thanks bro

 

[suislidE03]

Re: amp problem, please help

Maybe, thing is the guy thought he fixed everything on the first run but when i got it back it still did that. So this time its on him :dance:

 

[hellrider77]

Re: amp problem, please help

just to make sure, any one else experianced this problem? scott_f i know you are a treasure trove of amp knowledge, what do you think. i really don't want to go all the way to nashville to see mt amp tech over a peavey, ya know?

 

[Rich_S]

Re: amp problem, please help

It could be as simple as a dirty pot. Try spraying each of them with some Radio Shack tuner cleaner, then twisting them back and forth a few times.

More likely, its a bad contact that changes with temperature. Bad solder joint on the PC board, perhaps. You'll probably want a tech to find and fix it. Finding it's tough, fixing it easy.

 

[Scott_F]

Re: amp problem, please help

Not a chance there are tubes on this amp maybe? If so, start swapping them out.

Went and downloaded the manual. No such luck on teh tubes. Bad solder joint is a most likely culprit.

Here's a question... when it is having problems, can you unplug your cable and then plug it back in and make the problem go away? If so, you've probably loosened a solder where the input connects to the circuit board. In any amp, input jacks take a beating, more so with some guitarists than others, but it's a weak link on a circuit board amp. They are usually cheap to begin with.

If you have any electrical aptitude at all, you can probably take it apart and get a wooden chopstick and start probing the amp while it's having this problem. If it's a bad solder joint, you can often tap it with the stick and figure out which place it is. that's one of my regular trouble shooting devices. I snag all the chopsticks at the table when we go to PF Changs. (actually, the ones at PF Changs are plastic and rarely break)

If you are not comfortable doing that, take it to your tech. Doesn't Peavey offer a 3-5 year warranty like Fender? Is it still under warranty?

 

[hellrider77]

Re: amp problem, please help

nah, ive tried takin the input out and wiggling it but it doesn't help. on the post gain it only helps to turn it way up, around 7, then play for a little while, like 10 to 30 minutes then it starts swelling the volume back and forth then boom, the output gets normal and you can turn it back down. i have used contact cleaner on all the pots and none are scratchy or anything. im starting to think that its gotta be a bad solder somewhere, but what confuses me is how it corrects itself after playing a little while and will stay like its supposed to until you turn it off. then if you turn it right back on, it starts the problem all over again. i am not very adept at electyronics, but im gonna try the chopstick thing to see if i can locate a bad solder, i think i may be able to fix something that simple myself, provided i can find it. before i start i got one question though, i have read about how you have to discharge caps on a tube amp to keep from getting electrocuted, is there any such dangers i should look out for on a solid state?

 

[Scott_F]

Re: amp problem, please help

If you have no idea what you are doing, take it to a tech. There is no need to drain the caps if you are pushing around with a chop stick. The amp has to be on for this trouble shooting method to work.



This is probably one for a repair shop.

 

[hellrider77]

Re: amp problem, please help

i have been wanting to learn some electronic repair anyways, so im gonna try it myself. if you don't hear from me in a few days....................call an ambulance.

 

[Breaking the law]

Re: amp problem, please help

i have been wanting to learn some electronic repair anyways, so im gonna try it myself. if you don't hear from me in a few days....................call an ambulance.

Be careful, man.. I once got a healthy dose of voltage from my old Laney.. I had it opened up and my other hand accidentally touched a screw on the back of it while I was probing away. Ouch. Basically trought the heart, too. :smack:

So keep your other hand in yer pocket!

 

[Scott_F]

Re: amp problem, please help

if you insist on doing this, poke around with one hand behind your back.

take off all jewelry first.

read up on how to make a resistor with some wire and two aligator clips to discharge your capacitors. Since we don't have power tubes here, touch each lead on all the big caps and leave it there for at least 30 seconds.

Before opening her up, yank the power cord out of the wall while playing at volume. Keep playing. The decay you hear indicates that a lot of the charge in teh capacitors is draining.

Once you get the amp chassis out on a safe work surface, turn it back on with speakers plugged in and start probing with something wooden or plastic. chopsticks are a time proven favorite.

Not sure about how the amp is designed, but I've encountered problems with pots being wired up funky and you end up having to loosen up several connectors. Be sure to take a digital picture first if you have a lot of stuff to "unplug" off the board. Makes it easier to go back later. You might even sketch it out as well.

 

[Scott_F]

Re: amp problem, please help

You'll be building a 5E3 before too long. BE careful, it's addictive.