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I have this tube amplifier that I picked up at a garage sale, it even came with the original speakers. After I cleaned it up and made sure all the connections were good, I plugged it in, and it worked beautifully. So I was happy...till about 2 months later (present time)
It's a Panasonic M.F.B. Stereo Amp, Model EA-801. (I used Google for over an hour, and couldn't find one shred of info on it) It uses a couple of 12AX7's for the preamplifier and tone controls, plus one more, (for a high gain phono preamp would be my guess) there are a pair of 6AN8's used for the motional feedback system (damping and low frequency cut-off) Then there are 4 EL84's, 2 for each channel, for a push-pull output stage.
I noticed today that my left channel completely vanished, I poked around at it for a bit, and noticed if I move a 1M ohm resistor just right it works. A soon as I let go it cuts out again, so it's time to rebuild it a little. I also noticed that some of the oil caps are starting to leak pretty bad, like almost dripping out...Oh yeah, and just about everything in this amp is made by Matsushita (known today as Panasonic)
I am not sure what type of capacitors I should replace the old ones with Here's a pic of one of the oil capacitors: Think they are polyester, or polypropylene?
There are also 2 thin black rectangular capacitors in the input area that are rated at 50V and 3.3nF, any guesses? I'd guess ceramic, but not sure, I'm unable to get a good pic, that's why there isn't one...
I also want to replace all the resistors with new ones, but I'm unsure about the power ratings Here's a pic of the 2 different sizes: (any idea of the power ratings?)
Hopefully my questions are clear and some of you can help me out...
Well it's broke now, I threw the parts back in it and plugged it in and it wouldn't work...I smacked it pretty hard and one of the tubes gave a big internal spark and now i get a huge 60Hz buzz on the output x.x Eh, I wanted to get matched tubes anyway
Registered Member #5436
Joined: Sun Jun 24 2012, 01:44AM
Location:
Posts: 39
Hello,
You must replace all the paper wax and oil caps. They will explode and destroy the tubes. The tube hat arced is most likely the rectifier, and the arcing is caused by over current draw by leaky electrolyte capacitors. They also must be replaced.
The tube that arced was one of the EL84's, the rectifier tube is brand new, and is working as it should. I do plan on replacing all of the caps, I just don't know if I should use polyester or polypropylene oil caps...any ideas?
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Tube Amplifier Rebuild Questions
