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'64 Vox AC30

Discussion in 'Amp Tech Center' started by corliss1, Oct 21, 2020.

  1. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Fiiiiiiiiiine :D

    The front - some serious mojo

    1.JPG

    Back - also serious mojo

    IMG_5345.JPG

    So British

    IMG_5346.JPG

    Someone thought they had a good idea back in the day...

    IMG_5347.JPG
    Do...do I see this actually had a service done? That can't be right........(notice extra tube for the tob boost circuit inside the amp there)

    IMG_5348.JPG

    Numbers


    IMG_5349.JPG


    Has the correct multi-tap PT:


    IMG_5350.JPG

    So if you've never ripped apart a Vox before, the first thing you have to do is unscrew the speaker wires from this little terminal board.

    IMG_5351.JPG


    After that, you'll quickly realize that nothing is holding these amps together. They sit on a piece of plywood that is attached to.............nothing. It sits in rails on each side and just holds the chassis up. Here we can see it starting to slide out.

    IMG_5352.JPG

    Back with original speakers:

    IMG_5353.JPG
     
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    The customer complaint - "Just got it today. Had it shipped. Hums, and isn't very loud."

    Well, that doesn't sound like an AC30. We'll make it loud, and teach it some words so it doesn't hum anymore. (not even sorry about that joke)


    Speaker close up:

    IMG_5354.JPG


    First sign this could get interesting - looks like some shipping damage. Remember how I said that plywood isn't attached? What most likely happened is that the plywood slammed into the back panel, and popped this nut insert loose, breaking away some wood in the process. No big deal - we'll epoxy it in later on when I get to that point.


    IMG_5355.JPG

    Only logo left on it:


    IMG_5358.JPG


    Guts removed:


    IMG_5359.JPG

    More evidence of actually being serviced:


    IMG_5360.JPG

    Let's flip it over and get that plywood off to see the guts. That middle screw is also holding on the top boost board bracket.


    IMG_5361.JPG


    More servicing. It's not the prettiest solder work, but it's all solid.

    IMG_5362.JPG

    Man, these resistors look cooked (file this away for later...)

    IMG_5363.JPG


    More cooked evidence:


    IMG_5364.JPG
     
  3. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Too cool, subscribed. :cool:
     
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  4. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Alright, so it's serviced pretty recently and doesn't need a cap job. Let's fire it up and see what happens. We'll grab a scrap piece of wire and hook it up to that terminal block so we can connect some speakers:

    IMG_5365.JPG

    And then we'll plug it in........oh, no we won't. It's still British...

    IMG_5366.JPG

    Made it more American, then we plug it in, and we get this:

    IMG_5367.JPG

    That's certainly not ideal. Half the power supply is redplating and that would definitely cause quiet and hum. And certainly could cause those cooked resistors.

    So...where do those connections go. Oh, to this broken wire that feeds half the power supply:

    IMG_5368.JPG


    So here's what happened. The previous service, which also included a replaced tube socket, seemed to shorten that wire. The wire was so tight it was pulling on the board, and broke. I couldn't reuse the old wire since it was so short, and even shorter after breaking, so I replaced the wire. That allowed the amp to actually function, but those super cooked resistors needed to go too. There were also 50% off spec.

    Clean that hole:

    IMG_5369.JPG


    New wire that actually wraps around the hole:


    IMG_5370.JPG

    Shiny new 1.5K resistors. Reused the original spaghetti except on one that was torn:


    IMG_5372.JPG


    So cooked:


    IMG_5371.JPG


    Nice pretty solder now:


    IMG_5373.JPG

    So that's where we're at. Gonna talk to the customer, probably recommend new tubes since I'm guessing those cooked like that for a while (and you can see the one side is burned more for sure) and then it'll be back to its home!

    As usual, these amps sound fantastic. Has all the "chime" and other Vox-y buzzwords attributed to this model. The trem is fun, footswitch is there and works.
     
    JamesAM, Piotr, Jon Snell and 2 others like this.
  5. CV Jee Beez

    CV Jee Beez Tele-Holic

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    Looks similar to my old '64. It was a copper panel with integrated top boost. Always good to see the Wima caps.
     
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  6. tubegeek

    tubegeek Friend of Leo's

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    @corliss1 nice guts! How much of the vintage value did you destroy by replacing the magic mojo original wire, d'ya s'pose?
     
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  7. Mr. Lumbergh

    Mr. Lumbergh Poster Extraordinaire

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    Noice. Sweet amp.
    My favorite sound in the world is a Tele or Gretsch running through a splitter into a Twin and an AC.
     
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  8. tubegeek

    tubegeek Friend of Leo's

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    They're little windows! Into a 4th dimension!
     
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  9. elpico

    elpico Tele-Afflicted

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    Wima still make excellent caps. I don't see them around here, probably because they're all radial format these days, but they're quite popular in other areas of the audio electronics world. Nelson Pass uses them a lot in his builds for example.
     
    CV Jee Beez likes this.
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