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Output transformer varnish (?) cleaning

Discussion in 'Shock Brother's DIY Amps' started by Tom Kamphuys, Jun 25, 2020.

  1. Tom Kamphuys

    Tom Kamphuys Tele-Holic

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    I've received the output transformer for my jcm800 6V6 build. It has some kind of varnish (?) on it that is not evenly applied.

    IMG_20200625_092639064.jpg

    What is that stuff? What is its purpose? Can I clean it? If yes, with what? If I choose to paint it, what paint/spray should I use?
     
  2. LetItGrowTone

    LetItGrowTone Tele-Meister

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    Makes it look legit. See, the side isn't smooth either. I'd leave it alone. :)
     
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  3. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    ^^^ for sure. What gets me is when the caramel or licorice goop from inside a transformer runs all down the leads. But I've learned to live with what I can't easily scrape off. The electrons will never know. :)
     
  4. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    It is probably epoxy or polyurethane potting leftovers.

    I would only consider painting the transformer if it were to be exposed for show type build.
     
  5. schmee

    schmee Doctor of Teleocity

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    By the way, I walked past your car yesterday, I think there's a pebble in the tread of the right front tire. Better take care of that..... :lol:
     
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  6. Peegoo

    Peegoo Poster Extraordinaire

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    OUCH! Tough crowd :twisted:


    Yeah, absolutely nothing to worry about. Some folks have really messed up transformers by trying to 'clean them up'.

    One of the worst things a person can do is clean off surface rust from a transformer's laminated plates. The plates are insulated from one another by a varnish; if you wire brush or sand on them to remove rust, it can create an electrical connection between the plates and the transformer will lose power as a result. Best thing is to apply a light coat of Rustoleum in your favorite color, and call it good.
     
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  7. Tom Kamphuys

    Tom Kamphuys Tele-Holic

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    You seem to know me quite well. I have to admit I've actually done that. :oops:
     
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  8. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Another vote for "looks good, leave it"
     
  9. tdoty

    tdoty Tele-Meister

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    From my transformer production days.......You can scrape it off ( a brass putty knife should work nicely). If it is hard and chips, it is likely "bake varnish"; nasty stuff that has to be baked to cure it. If it is somewhat soft and gummy, it is probably air dry varnish; a rather self-explanatory name. Epoxy varnishes tend to be black-ish.

    The Ampeg SVT transformers were done in "Permafill", a nasty concoction with silica flour and numerous chemicals that got baked after vacuum potting. We used leftover Permafill to patch holes in the concrete.

    Some customers (OEM level) were picky about appearances and scraping off excess varnish was part of the final step. We would wrap the lead wires in plastic (for air dry) or foil (for bake varnish, etc.) and scrape off excess that got on the leads with a dull paring knife. Other customers just wanted the lowest price and they got what they got; we didn't put a lot of excess labor into those.

    The uneven application is because the transformers are dipped and the excess runs off. Its purpose is to act as an added layer of electrical insulation. The varnish application process is known as potting, same as wax dipping pickup coils. I think it serves a similar purpose to potting, as well, by keeping the windings attached to each other and filling up the empty space in the coil, the steel, and the covers. I am not sure, however, that there is such a thing as a microphonic transformer. Some old, old transformers are wax dipped instead of varnished.

    Yes, I'm still a bit of a transformer nerd.
     
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  10. LightWeight

    LightWeight TDPRI Member Silver Supporter

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    Tom, I'm with you, this is our hobby, not our vocation. When I spend my time building something I try to make it look like I paid attention to details. That's what makes it "Hand Crafted" as opposed to the mass-produced stuff where the bottom line is most important. I received two "Classic Tone" transformers with the same thick caramel-colored varnish drips on the sides and I'm not sure what I'll do about it. I may just let it go, but I may also scrape sand and spray with clear varnish. Details make the difference.
    All the best.
     
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  11. Dacious

    Dacious Poster Extraordinaire

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    That's how Schumacher makes them. Anyone deducting points for this from your build - tell 'em get on the Macintosh Audio Self-Pleasurer's Forum.....
     
  12. Mongo Park

    Mongo Park Tele-Afflicted

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    This seems to show two camps here. Can’t stand to see a hair out off place and it’s all about the tone focus.
    More of a observation of human nature. If I can build it better than I can buy it I am in but lean more to the side of it is all about the tone. I use a lot of reclaimed transformers and I do clean the dust and Years of sticky cigarette smoke off them. So I can see both sides So smoke em if you got em, it’s all good as long as we are having fun, but good advice don’t mess with the innerds if you don’t know what they do. Once the box is closed up and I am enjoying the tone I forget about the few uglies inside the box.
     
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  13. tubegeek

    tubegeek Friend of Leo's

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    Not kidding about the "Perma," huh?
    Not microphonic (input transducer) - they can be an OUTPUT transducer though for sure. The laminations will "sing" because of magnetostriction.

    Usually not a very big deal - even unpotted, the lams are held awfully tight by a c channel or bolts. But it IS a thing.

    Transformer nerds are a very good batch of nerds!
     
  14. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Setup up your amp outside the chassis into a dummy load. Run signal in. Crank the volume all the way. Listen. You'll hear sound coming from the guts itself, and that is often a transformer "singing"
     
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  15. tubegeek

    tubegeek Friend of Leo's

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    And it NEVER knows the lyrics to the second verse!
     
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