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B52 AT100 worst amp ever - I need help

Started by bradtomko, February 24, 2010, 06:23:50 PM

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Hey, Im new to this site but i need help with my B52 AT100. Its basically a piece of junk. It was 800 new. its a triple rectifier and sounded awesome. The problem is, when i bought it from a friend, he said he blew a power tube, 6L6 GC, and it played for 5 min or so and then shut down. Its been looked at and "repaired" by a few guys. Im in school for electrical engineering and as sad as it is, we did VERY little with tubes. The amp will turn on and play for approx. 6 min and by that point, the power tubes are too hott to touch. They light up fine when its on standby but as soon as I take it off, they light up blue and there is a clicking noise, every time, coming from the side of the biggest transformer. The work done to it included 4 new Bugera (i know, JUNK) 6L6s, and 6 new capacitors including the big ass filter caps.

Id really like to be able to fix this amp. I know its almost ridiculous to ask help in trouble shooting with out seeing the amp in person but any advice on what to do on how/what to check would be great.

attached is the schematic and a photo of the power section

J M Fahey

QuoteB52 AT100 worst amp ever
How would you know?
How many other amps have you owned?
Quote. Its basically a piece of junk.
QuoteIt was 800 new
Ah, now I see.
Anything below $8000 is cr*p. ;)
Quoteits a triple rectifier and sounded awesome
Quotethe power tubes are too hott to touch
They always are.
"Normal" glass envelope temperature up to 200ÂșC. Ouch!
Quote4 new Bugera (i know, JUNK) 6L6s
How would you know?
(It's getting repetitive).
OK, now you see that if you want to bash Bugera, there are 14759 Forums out there; if you want to repair it, stick to real-life problems.
Let's start from the beginning:
1) Does yours work/sound?
2) What do you hear that worries you?
3) What are you doing when that happens? Is it repeatable? Does it always happen when you do something specific?


Well, if you are just going to take every expression of frustration and turn it around to make me look like I know nothing, i'll just be moving on. I've played hundreds of amps, you don't need to own one do determine if it sounds good or not. I wouldn't believe you if you'd say you've never called something junk out of anger. It's a decent sounding amplifier but has given me a lot of trouble. If you would have read my post before bashing it you would realize that they are too hot to touch after six minutes of blazing blue. Yeah, that's normal operation huh? Also, after dealing with 20 or so Bugera heads at my Best friends shop, I've made my conclusion about them. How do you feel about Bugera Power tubes? Oh wait, I don't care, I don't doubt your credibility, i'm just trying to fix my B52. I can see that i'm not going to get help if you are the only person replying. Thanks a bunch! This site just lost a user.

J M Fahey

Hi bradtomko.
Why are you surprised by my answering in the exact same tone you were using?
Please re-read the title that you gave to your posting.
As you see, after bashing the bashing, if you get what I mean, I asked you to get to the point and asked you a few specific questions, to be able to start helping you.
In other forums, maybe they follow your line, and add to the B52/Bugera/Crate/whatever bashing.
Do you get useful advice there? Don't think so.
So I repeat my well-meaning offer:
QuoteLet's start from the beginning:
1) Does yours work/sound?
2) What do you hear that worries you?
3) What are you doing when that happens?
Is it repeatable?
Does it always happen when you do something specific?


So, for starters, you could pull off the tubes and check that the power supply is providing correct voltages and doesn't have any failed parts.

If those seem to be allright then you could try with new tubes and properly adjusted bias. Most likely you'll be needing them anyway, whether you find problems from the PS section or not. Also, make sure that the bias circuit within the rectifier selector switch is working correctly.

Not to mention, check out what these "repairs" actually were.

That should get you pretty far.