Any tips/tricks for my first vintage tube amp repair?

jrblue

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From the OP, it's impossible to tell if you know what you're doing at all or are just stating stuff that is commonly, though not necessarily accurately, said about old tube amps. So it's hard to make suggestions, other than (1) follow all safety practices, fully; (2) do all basic inspection, servicing, troubleshooting, and testing before you jump into categorically stripping out original components that may be fine and better than anything you can replace them with, and (3) power up slowly with a variac to the correct voltage for the amp/year. BTW, "untested" commonly means "broken." It's how people commonly post stuff, covering their butts, in a manner that doesn't leave them open for returns and bad feedback when they ship something that's DOA. Obviously, most people are going to test something that will yield lots and lots more money if it works than if sold "untested." Much "untested" stuff is actually non-functioning, "ignorance is bliss" stuff. Of course, even dead equipment can be a good purchase depending on what's needed to repair it (and if it's not modded/messed up by the owner). Good luck with what, when working, is a good amp.
 

radiocaster

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What amps are you working on that, first, had that many electrolytic caps, and second, nearly all of them bad? This sounds fishy to me.
TWO amps. Sovtek. More than 25 years old. In some places there were two 220 microfarads in series, plus for the bias and heater circuits. I don't feel like looking at the schematics, but there were a lot.

Also I changed the filter caps on an Earth in the early/mid 90s. That amp was probably less than 20 years old, yet changing those fixed it, although I wasn't so systematic in my repairs back then, even though I had taken electronics classes.
 

King Fan

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This is gonna be an interesting thread, @BoomTexan . There are two distinct camps on amp restoration questions, and you're gonna hear pronouncements based on opinions. And a lot still depends on your goals, as @Lowerleftcoast says. I hear ya:

I'm not planning on doing it for a quick profit. I'm gonna try to get it as clean and nice as possible as a showcase project for my fledgling repair business,

I'm glad you're not doing it just to flip for $$$. But showcase what? Pure function and reliability, shiny, reliable, all-to-spec, high-grade, long-living modern parts? Or pure restoration that looks as vintage as possible? Or (likely) some hybrid? Reliable? Pro-looking? Optimal sound? The $1.50 cap or the $15 boutique cap? Another example: Replacing the cap cans will look way more vintage; separate caps may function even a bit better and make future repairs easier but look *way* wrong visually. As mentioned above, you can buy an ESR tester, but caps often fail even when ESR is intact.

FWIW in dozens of threads like this I see most of our smart experienced amp techs replace the electrolytics -- other than collector appeal, the 'mojo' of old caps is not sonic; at least a drifted old resistor may have drifted upwards to a nice-sounding value, but e-caps? Not so much.

Anyway, between the two opposite camps and the two opposite goals, you're playing 4-D chess (let's make the 4th dimension time -- time to next failure). Your move. :)
 




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