Bugera 6260-212 help!

[frpax]

Hey guys! New to the forum here, but have been lurking for a while.

I have a Bugera 6260-212 combo amp that has been a pain since I got the thing. Not being one to let go of equipment without plenty of justification, I thought I'd seek some help here!

So. Here's the problem:
When I turn the amp on (I power it up on Stand By for a couple minutes, then flip off Stand By), the amp works fine for a minute or so.
If I play on the clean side of the Clean channel AND with the guitar volume down, I can play for several minutes. But, if I switch to Crunch or the Lead channel, and/or turn the guitar volume up to 9 or 10, then the amp suffers a SIGNIFICANT loss of volume to where you can barely hear anything, except a faint, very fuzzy tone. When I turn the amp off (onto Stand By first), the Stand By light doesn't turn off immediately, but stays aglow for several seconds, then slowly fades out. Then, after a minute or so, I power the amp off. After it has cooled off, when I power the amp on again (properly) the whole sequence of events happens all over again.

So, I definitely need some help from the experts HERE!

By way of background, when I first got the amp, everything was A-OK. Then while playing one day, I heard a POP and FIZZING sound and then the amp was dead in the water, so I figured I blew a tube (since I had read that the OEM tubes from Bugera are generally regarded as crap) and had a buddy of mine re-tube ALL the tubes with matching JJ's. After that, It worked fine for MAYBE 5 hours, and then started this new issue.

I'm not afraid to dive into fixing this problem myself, as I am fairly good with a soldering iron.

BTW, the amp IS still under warranty, but I am in the Phoenix area and the nearest Bugera Service Center is in Las Vegas. Shipping the behemoth 6260 is cost prohibitive and driving it there is not my idea of fun. I can't decide which would be more expensive, shipping it or the gas to drive there & back!

Anyway, since I had it re-tubed locally, I figure I voided the warranty anyway. Besides, I like fixing things myself.

SOO, any help from you excellent people here would be GREATLY appreciated!

Thanks all,

Frank

PS, I can take pictures of any parts you want and post them here if you tell me, in detail, what to take a pic of AND how to get to that particular part!
~F

[g1]

Can you wiggle the tubes around in their sockets a bit while it has quit and see if it comes back, like it did before when he changed the tubes? It sounds like there may be a bad connection somewhere.

[frpax]

Can you wiggle the tubes around in their sockets a bit while it has quit and see if it comes back, like it did before when he changed the tubes? It sounds like there may be a bad connection somewhere.

I will try it, but (just to play Devil's Advocate) wouldn't a loose tube just be loose and affect the sound, regardless of whether it's been heated up or not?

[g1]

I'm thinking more of a bad solder joint on one of the tube sockets. Or elsewhere on the board the sockets are mounted on, and getting flexed when the sockets are wiggled.

[frpax]

I'm thinking more of a bad solder joint on one of the tube sockets. Or elsewhere on the board the sockets are mounted on, and getting flexed when the sockets are wiggled.

I see. Could it be ANY tube? Or just the Power tubes? Or pre-amp tubes?

[g1]

Likely a preamp tube.

[frpax]

Likely a preamp tube.

Great... They have those metal covers and I cant figure out how to remove them. Or do I even need to?

[g1]

Usually, you push down a little, twist counterclockwise a little, then pull up and off.

[frpax]

Usually, you push down a little, twist counterclockwise a little, then pull up and off.

OK, got them off.
Wiggling them didn't cure the problem.

[frpax]

I didn't just wiggle the pre-amp tubes, but all of them. I used a paper towel and didn't touch any tube with my bare fingers.

[Enzo]

You can touch them with your fingers all you like, don't burn yourself. it is projector bulbs and spotlight bulbs you cannot touch, they run MUCH hotter.

Changing tubes has no effect on your warranty. Going inside the chassis and soldering stuff is what kills warranties.

Next time this happens, pull the guitar cord plug out from the input jack and plug it into the FX return jack, or the power amp in jack if it has one. Is that also weak or does it come out strong?

Joints are soldered, and solder is a metal. Metals expand and contract with heating and cooling. it is utterly conceivable that warming uo might affect a connection.

With the covers off teh small tubes, look at each one to see two small orange glowing spots. Those are your heaters. When the sound dies, look carefully at each tube and see if either spot in any of the tubes has gone dark. Some may appear darker than others, but if the amp is working, then that is normal. The difference that matters is not lighting up at all, I'd not worry over one seems less bright.

You may have an electronic problem, an open or broken connection-ed grid resistor on a triode will cause problems like this.

[frpax]

You can touch them with your fingers all you like, don't burn yourself. it is projector bulbs and spotlight bulbs you cannot touch, they run MUCH hotter.
I was not aware of that, but I figured it was better to safe than sorry.

Changing tubes has no effect on your warranty. Going inside the chassis and soldering stuff is what kills warranties.
OK, but still, shipping it or even driving it to Las Vegas just won't happen. Besides I like to sort problems out and fix them. Sense of achievement, ya know?

Next time this happens, pull the guitar cord plug out from the input jack and plug it into the FX return jack, or the power amp in jack if it has one. Is that also weak or does it come out strong?
OK, it did it and I plugged the guitar into the FX Return jack (it only has a Power Amp OUT jack on the back). I got good strong volume doing this. However, it was only a CLEAN tone, no matter what channel I had on the front panel. No Crunch or Lead tone at all.

Joints are soldered, and solder is a metal. Metals expand and contract with heating and cooling. it is utterly conceivable that warming uo might affect a connection.

With the covers off teh small tubes, look at each one to see two small orange glowing spots. Those are your heaters. When the sound dies, look carefully at each tube and see if either spot in any of the tubes has gone dark. Some may appear darker than others, but if the amp is working, then that is normal. The difference that matters is not lighting up at all, I'd not worry over one seems less bright.
Every one of the pre-amp tubes had the two small orange glowing spots.

You may have an electronic problem, an open or broken connection-ed grid resistor on a triode will cause problems like this.

I figured it might be a cracked solder joint somewhere or some other small component that only fails when hot.

OK. So. What next?

[The Dude]

Do ALL of the filaments stay lit when the amp malfunctions? My bet is that you are losing filament voltage somewhere. Check visually and/or with a meter.

[frpax]

Do ALL of the filaments stay lit when the amp malfunctions? My bet is that you are losing filament voltage somewhere. Check visually and/or with a meter.

If by "ALL filaments", you mean those two orange glowing spots near the top of the pre-amp tubes, then YES, they are all on both prior to and after the amp malfunctions. Visual check. I have a multi meter, but I don't have the first clue how to use the danged thing!

[The Dude]

Yes, the "glowing spots". Often, they might stay lit up a bit as the filament voltage decays. Be sure to look at them for a bit after you lose volume. And, not meant at all to be condescending, but I'm not sure you should get into the amp if you don't know how to use the multi-meter.