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Rectifier tube keeps blowing

I have a cheap Chinese tube amp. It uses a 274B rectifier tube from Valve Art. Once during listening, the rectifier tube blew and so did the fuse. I replaced the fuse and replaced the rectifier with another 274B from Valve Art. Then, days later, I turned the amp on and same thing happened at power up. Fuse blew, rectifier went. I changed the fuse again and added my third (and last) rectifier tube. Every time I turn the amp on now, I take a deep breath and turn my head. What the hell is going on here? I think a rectifier turns AC to DC (dangerous). If the rectifier goes, than damage could occur to the transformers,tubes or the whole amp could take a dump. I just put some great KT77's in here and I don't want anything bad to happen. Is it the Valve Art tube? Is it shoddy workmanship in a cheap Chinese amp? Help.
devilboy
xti16
1,495 posts
 
My first guess would be a bad cap in the filter section of the power supply. You seem to have an over current condition. Second guess would be a bad driver tube then maybe an output tube. I would have it checked out by a good tech. There are many more components than what I mentioned that could be the culprit. May even be a cold solder joint. All guesses.
detredwings
162 posts
 
The previous response is correct. You have an over current condition. Since you keep putting tubes in it, my guess is you don't have any experience with this kind of thing? Power supplies can be dangerous and if you don't know what your doing I would suggest you take it to someone who does. I'm only suggesting this because the high voltage stuff can hurt you.

P.S. don't waste any more tubes until the problem is fixed.
rrog
1,958 posts
 
How do you know the rectifier tubes are blowing and not just the fuse? Are you using slow blow fuses?
atmasphere's avatar
atmasphere
7,068 posts
 
I would not be surprised to find a bad filter capacitor in the power supply of this amp.

However, you did offer a clue to an alternative explanation:

You just installed a new set of 6550s in the amp. Did the rectifier by any change begin blowing after that? Are the 6550s properly biased? If not, this could pose a problem for the rectifier, *if* the power supply or the power supply design is somehow marginal.

IME the Chinese stuff is cheaper but you pay for it in service headaches.
trelja
3,215 posts
 
Detredwings gives the best advice, "Power supplies can be dangerous and if you don't know what your doing I would suggest you take it to someone who does. I'm only suggesting this because the high voltage stuff can hurt you."

As upset as you are, consider it a blessing that the rectifier and fuse are blowing before something more serious occurs.

If the filter caps do check out OK, look around for a heavy duty short somewhere in the power supply. After that, I'd be suspicious of the power transformer.
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