Show me your Variac

Discussion in 'The Workbench' started by Rotorcraft230, Jun 27, 2020.

  1. Rotorcraft230

    Rotorcraft230 Well-Known Member Premium Member

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    DE941B72-9FD9-489E-9F07-85D272958CEE.jpeg I finally bought a Variac. A bit unusual with the black wrinkle finish. Works great all original and a great price. Paid 75 bucks shipped. Anybody know what year it may have come from?

    show me yours

    Mark
     
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  2. Biddlin

    Biddlin Well-Known Member

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    I'd have to ask my proctologist for the Xrays.
     
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  3. Exotic

    Exotic Well-Known Member

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    well ,tell us how u do? can u turn the variac way down and blast the amp ,and presto u sound like eddie van halen on vh1? album?
     
  4. Rotorcraft230

    Rotorcraft230 Well-Known Member Premium Member

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    Na it’s for building and repairing amps.
    In suppose you can use it for that, like the EVH thing
     
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  5. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Yours looks vintage. I got a used one recently but opted to get one with a 3-prong plug and receptacle. And, no, not using to sound like Eddie. I’m using mine to bring my builds up to power slowly. It cost $110 off the bay.

    upload_2020-6-27_16-36-22.jpeg
     
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  6. Rotorcraft230

    Rotorcraft230 Well-Known Member Premium Member

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    8F237776-195B-47D8-B57C-DBBCD8F27005.jpeg
    Nice, kinda hate to mod it but I think I should. 3 prong power chord and I’ve already made this to adapt for the output. Just need a longer screw and a spacer to attach the alligator clip to
     
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  7. william vogel

    william vogel Active Member

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    I don’t know 100% if this is true but I read that the first time EVH plugged in his Marshall, it went up in smoke. He got a variac to lower the voltage. Is it possible it was a 100 volt model?
     
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  8. South Park

    South Park Well-Known Member

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    It’s a beater got it a the dump 42DB36B3-07C3-4AB3-BB94-088A4E2AA2EC.jpeg
     
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  9. Chris-in-LA

    Chris-in-LA Well-Known Member

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    I heard Ed do an interview recently and he said he bought his first Marshall, tried to make it work, but had it on the 240v setting. That experience got him thinking that he could experiment with different voltages for his amp and that led him to getting the variac. Don’t know if he blew it up or not.

    I think this was the interview, either way it was interesting.

     
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  10. Sapient

    Sapient Well-Known Member

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    The crunch I get out of my PLEXIs is outstanding now. Finally ..more control. :yesway:



    [​IMG]
     
  11. william vogel

    william vogel Active Member

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    I read that he was working in a club and they had an old plexi in the back line. They never used it and ed talked them into paying him with the amp for his hours worked. When he finally got it, he took it home and plugged it in. Smoke Cloud!!
    Could have had bad caps but this was the whole variac thing. I’m just wondering if it was a 100 volt and he had to use the variac to get the amp happy. Ed’s ego gets in the way of the truth. He let Dave talk him into lying about the variac and I just wonder if there’s more to the story. I’ve variaced down to 90 volts and loose to much of the amp from 120 volts. 90 into 100 seems about the right ratio for 120 into a 100 volt design.
     
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  12. junk notes

    junk notes Well-Known Member

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    I am hoping to use variac's to get these tones with the SV20 soon. EVH had great results. At least through his PLexi's. Especially 12301

     
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  13. Seanxk

    Seanxk Well-Known Member

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    Out of interest, what Amp rating is it.
     
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  14. Rotorcraft230

    Rotorcraft230 Well-Known Member Premium Member

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    amp rating is 7.5. Plenty for what I want to use it for
    Edit. These Powerstats made by Superior Electric are built like tanks, that’s why there are a lot of them still out there I think mine is from the 50s. It weight probably 12 pounds.
     
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  15. Rotorcraft230

    Rotorcraft230 Well-Known Member Premium Member

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    They started making then in 1938
     
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  16. junk notes

    junk notes Well-Known Member

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    Sure. Listen to what I posted and then decide.
     
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  17. Chris-in-LA

    Chris-in-LA Well-Known Member

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    I’ve heard people say that if you let an amp sit for a long time you should bring it up slowly. I would assume that could be another use for a variac. But, how slow is slowly?
     
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  18. South Park

    South Park Well-Known Member

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    What you are doing is resetting the filter caps to a certain voltage . It is what a lot of raideo repair techs do to really old stuff. You ramp it up 50 volts a hour . What is nice to do with a Variac is power up a new build on low voltage to test amp draw . The transformers don’t care just don’t run the tubes on low voltage
     
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  19. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Quick question, no tubes but what about a tube rectifier? I assume that you will not send any b+ to the filter caps without a rectifier.
     
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  20. neikeel

    neikeel Well-Known Member

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    The easiest way with a tube rectifier is not to use the variac. take a 2w 100k resistor and clip it across the terminals if the stand by switch. All tubes out except rectifier.
    Switch amp on (but not the St by). Now all the HT is going through the amp and the 100k limits the current. As the caps reform the voltage on the caps goes up snd the voltage drop across the 100k goes down. It will start at 200v plus, drop to 70v After a few mins and, depending on the condition of the caps, dropping slowly over a few hours. Good caps will be down below 2vdc within 4-6 hours. Satisfactory, but not perfect, under 10vdc.
     
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