Old tube amp needs fixing. (With video)

jakeimnotshure (45)in #music • 7 years ago

I got this amp from an old lady who knew I liked amps and guitars and such. She said her father built it from nothing. He just knew how to do it. I don't know if he had formal training or not but the thing works!... Kinda.
The knobs aren't labeled but I'm pretty sure they are: input, tone, and output.

It's also hard to see the tube part number. Making it hard to replace them. Same for the transformers.
Here is why I said I dont think hes had formal training. The wiring underneath this is just a mess. I know capacitors need to be facing a certain way to not cause interference and noise. These look like they were slapped in however they could fit. Which might be its problem.
Ok here is a video I made to show how this thing sounds and what I mean when I said "kinda" works.
I'm running this through @johnbutler 's Marshall MC412A cabinet and with his De Armond guitar. I'm a drummer though so no solos lol

Thanks for stopping by
Steem on!
-Jake

#tube #amplifier #guitar #electronics

7 years ago in #music by jakeimnotshure (45)

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amberyooper (69) 7 years ago

To start with, the way it is wired is called"point to point" wiring. There's no circuit board, just parts soldered from one hookup point to another.
The fact that it works and makes sound means that both transformers are good.
It's possible that one or more of the can type capacitors are leaky, which means they aren't holding the amount of electrical charge that they should be holding.
Don't stick your hand in there while it's on, that thing probably runs somewhere in the 300-350 volt range.
I think the controls are volume, treble, bass, guessing from what it sounds like in the video when you mess with them. You probably have a weak or bad tube in it somewhere. The 2 metal covered tubes are probably preamp tubes, you can get glass tube replacements for them.
The tall glass tube next to the big transformer is a 5Y3, it's the rectifier tube, basically the high voltage diodes.
The power tubes look like 6K6s, if I read the numbers on the glass properly.
There's an octagon shaped mark on the side of each of the metal cased tubes, that has the tube number in it. All I can see in the pictures is 6S, it should be something like 6SN7 or 6SL7 or 6SK7. The glass tube with the brown plastic bottom, I can't tell what that is. It should have markings on the side of the glass, but sometimes they're on the top of the glass. It'll probably have a 6 followed by 1 or 2 letters and then a number.
I hope that helps you out somewhat.
Those old home made amps are fun to figure out.

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jakeimnotshure (45) 7 years ago

Thank you for the information. This is awesome! Ill have to do some more research. Any idea on how to test the caps?

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amberyooper (69) 7 years ago

Well, the easy way is with a capacitor tester, but you probably don't have one of those. Other than that, they're pretty hard to test.

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jakeimnotshure (45) 7 years ago

I should've figured that lol
Thank you for the help. I'm a small time audio engineer from MO. I went to school in nashville for audio. I love electronics and haven't had the time to get proper schooling for it but I'll take any help I can get. Thank you for commenting. Ill post more soon.

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amberyooper (69) 7 years ago

You're welcome!

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johnbutler (54) 7 years ago

Seriously though, we need to find a use for this lol. Hearing it through the my cab makes me want to do things with it... I never realized it could be so clear. I just had a weird thought, and it may sound stupid. Could the pulsing/whooshing sound have something to do with resistors (because homemade with no way to test what kind if load it can take?) Besides the odd arrangement underneath haha. Idk, the thought just occurred to me.

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