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Thread: How long does an amp stay electified and dangerous after switch-off?

  1. #1
    Neophyte surfaday's Avatar
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    How long does an amp stay electified and dangerous after switch-off?

    Hi All,

    I just got my first tube amp, a Vox AC4TV. I'm happy with the sound but I should belong to tinkerer's anonymous - I just want to get in there and swap tubes.

    From my noob research, it appears Vox amps are known for inconvenient tube access. And indeed, the chassis needs to be removed for me to get at the tubes.

    Also, I have read everywhere that you need to be careful what you touch in there or electrocution will be the result. (The info is mixed on death or just pissing your pants, but either way is doesn't sound like fun nor do I want to find out the hard way).

    So my question is: does the electrical charge eventually bleed off and go away after unplugging an amp? If so, how long before it would be safe to go in there? And, exactly what am I watching out for?

    Thanks for the help!

    Walt

  2. #2
    Axellent Member pictoratus's Avatar
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    This doesn't answer your question directly but is a good place to start.

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  3. #3
    Neophyte surfaday's Avatar
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    Thanks for the great safety tip article. That alone might make me wait a while and re-contemplate what I am planning.

  4. #4
    Neophyte surfaday's Avatar
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    Just changed the tubes in my Fender Champ 600. Why can't they all be like that? Oh well.

  5. #5
    AT Member Petawatt12's Avatar
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    Some amps have bleeders for the caps, but most don't like Fenders. They'll stay electrified for a long time. BE CAREFUL!!!
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  6. #6
    Neophyte surfaday's Avatar
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    Well I did it! And I'm still here! Whew. Left it unplugged overnight, for whatever that was worth. Still didn't take any chances and took my time and was very careful.

    On another note: I found that Eurotubes is located less than 30 minutes from me! What a great bunch of guys. I went and picked up a couple of JJ tubes and love them! And no waiting or cost for shipping! Woo hoo! Going to switch out my Fender Champ 600 to JJ's too next week. At least those are on the outside.

    Thanks for the input everyone.

    Walter

  7. #7
    Axellent Member Jammin'John's Avatar
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    I grab a wire with alligator clips.
    I clip one end to the chassis and I touch each filter cap to drain them.
    I then get out my VOM and make sure there is no juice lingering.

    JJ

  8. #8
    Axetastic etechstan's Avatar
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    Last year I got zapped by a 480v RF amplifier that I did not give enough time to discharge. All I remember is a bright flash and severe pain in my right arm. I know it had lost some power before I got zapped but I really learned a lesson. The warning label on the amp states to wait three minutes and I do so, then I take a screwdriver and jumper and short it to the chassis just to make sure there is no charge.
    I don't play guitar because I'm good at it, I play because it's fun!!

  9. #9
    Axeaholic Hu Duck Xing's Avatar
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    Ah! Fun with caps! I used to work for a small company that made disco equipment. One was a super strobe light that used the landing strobe from a 747. They would easily light up a few city blocks. I used to build them ten at a time, and there was a bleeder circuit. Well, I forgot to put it in one of them. I finished the assembly, and went to move it off the bench. Without the cabinet installed, the two easiest handles to grab were the TWO 660 VOLT, OIL-FILLED CAN CAPS! Every muscle in my body violently straightened out, throwing me across the room. The steel chassis hit the wall so hard, it was bent into a V shape! Had a headache for a day. That's about it. I also stuck my fingers into a wall socket, when I was 3.
    Ya can't pick up a turd by the clean end

  10. #10
    Axe-honerated zontar's Avatar
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    Quote Originally Posted by Hu Duck Xing View Post
    Ah! Fun with caps! I used to work for a small company that made disco equipment. One was a super strobe light that used the landing strobe from a 747. They would easily light up a few city blocks. I used to build them ten at a time, and there was a bleeder circuit. Well, I forgot to put it in one of them. I finished the assembly, and went to move it off the bench. Without the cabinet installed, the two easiest handles to grab were the TWO 660 VOLT, OIL-FILLED CAN CAPS! Every muscle in my body violently straightened out, throwing me across the room. The steel chassis hit the wall so hard, it was bent into a V shape! Had a headache for a day. That's about it. I also stuck my fingers into a wall socket, when I was 3.
    Glad to hear you survived...
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