Amps volume going up and down.. whats wrong?

[suislidE03]

Hi guys, just got a Laney VC50 from a guitar center and Ive been messing with it for about an hour or so. It starts up fine and all, but when im playing the amp doesnt put out any sound over half the time. When i play sometimes the volume will fade in and work fine for about 10 seconds, then it will just go quiet again, and do this over and over. Both channels work, as well as both drive boosts. I checked the power tubes, both glowing nicely. I looked at the preamp tubes, and I noticed all (6) are glowing, but the tube in the first position is glowing about half (guess) as much as the other 5. Could that possibly be the problem or could it be something inside? ANY help or recommendations are gladly welcomed.

 

[RiffGuy]

Re: Amps volume going up and down.. whats wrong?

I had the same problem. It was a while ago, but I think replacing the preamp tube fixed the problem. I also remember it was glowing less than half as bright as it should have.

 

[suislidE03]

Re: Amps volume going up and down.. whats wrong?

Did you have the exact same problem or were the circumstances different?

 

[RiffGuy]

Re: Amps volume going up and down.. whats wrong?

Well, the amp was no Laney. It was a hybrid Crate with a single preamp tube, but the problem was the same: all of a sudden the volume would just drop way down, come back, drop again. Very, very annoying.

 

[suislidE03]

Re: Amps volume going up and down.. whats wrong?

Alright i appreciate it.. I just hope its one cause my amp has six pre amp tubes i DONT want to have to spend $100 on tubes right when i get my amp.. but i can get a discount if its a big problem. Also, after leaving it on and playing for about 2 hours the problem actually stopped... it works fine now, but it has done it once after i was playing on it for about 45 mins. Thanks for your help.

 

[Brow]

Re: Amps volume going up and down.. whats wrong?

If I was in that position after buying an amp I'd take it back to the shop and get the amp either repaired (at their expense) or replaced. Did you buy the amp new?

Craig

 

[XSSIVE]

Re: Amps volume going up and down.. whats wrong?

are you playing at low volume or loud gig like volume? i have a similar problem with my peavey ultra plus head. at low volume the volume will go from where i set it to lower and back and forth now and again on its own. but when i crank it up to a loud gig volume it doesn't do it. i replaced every tube in the head with brand new JJ's and it still does it at low volume...i have no clue what it is. i e-mailed peavey and they said replace the tubes (that's why i did it) and that still didn't help.

-Mike

 

[Gearjoneser]

Re: Amps volume going up and down.. whats wrong?

Swap all the pre tubes backwards, so the 6th is now the 1st, if you don't have extras.
If the problem goes away, it was one of the preamp gain stage tubes getting ready to die. The store should just hand you a couple for free, or let you exchange the amp.
If you change all the tubes and it's still doing it, it's likely that a filter capacitor is slowly dying. Most other components just fail automatically, but those usually act up for awhile before going kapoot.

 

[suislidE03]

Re: Amps volume going up and down.. whats wrong?

Yea i thought about doing that, its just that this is my first tube amp and im still a little hesitant about diving head first into its electronics and such. Dont get me wrong, I will soon, im a very DIY person.

Also, I got it from guitar center used ('99 model, these amps arent made anymore) and the tubes are GT 6L6R (aka 6L6B) with noname preamp tubes. I was pleased that it came with two Celestion G12T-75 speakers though.

 

[suislidE03]

Re: Amps volume going up and down.. whats wrong?

OK, I checked the preamp tubes again and I realized none of them are at fault. So, Im assuming its a problem inside the amp, and that I would have to send it to someone to get it fixed.... which i absolutely hate. If you guys think its one of the capacitors, how much would you think someone would charge to replace it/them?