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Ampeg V4B blowing fuses

Discussion in 'Amps and Cabs [BG]' started by ashbory, Jul 25, 2001.

  1. Can anyone with some experience in these things help me.

    Heres what happened...
    I turned it on, it made a horrible noise. I turned it off.
    Turned it on again, no horrible noise, power tubes were glowing normally, took it out of standby and the fuse blew.
    After that it blows fuses as soon as I turn it on, even with the standby on.
    I opened it up and the capacitor that connects to the ground switch has popped. I am not sure if this is the cause or an effect of the problem. I have not been able to find a replacement part in the local electronics stores either, (its 600V, .047uF).
    I also noticed the wiring in the AC plug was coming apart and I have replaced the plug.
    Other than this the amp has worked fine for quite a while.
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Perhaps the one of the diodes that convert AC into DC has blown, and now the amp gets AC. That may account for the noise and probably for the blowing fuse too.
    Take it to a repairman that has experience with tube amps.

    I had something like that with my V-4B too, it was one diode after all.
  3. save some money and make a splitter box yerself! sheesh, 295DM for one! arrgghh!!

    just call me number 8 wire man!
  4. Arrrrggghhhh! Wrong thread!

    What I meant to say was...

    does that capacitor over the polarity actually do anything? mine's disconnected as well...
  5. and please don't poke around in it if you aren't 100% sure what you're doing, there's some seriously high current running through these things, even when unplugged. But that's probably a "duh".
  6. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    How can there be any current when it's unplugged? :confused:
  7. oo0o00o0oo


    Apr 30, 2000
    The big caps in tube amps have a residual charge. The filter caps I think...could be wrong tho.
  8. I know! :eek: I am in my second stage of Electronic Engineering and only now am i learning why! I mean many of us sparkies learnt the hard way aye!

    So too, don't place your fingers across the active and neutral pins on your mains plug. I've had the caps in power supplies discharge through my finger. Don't ask how it just did! Pheew!


  9. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    Eeee...thanks for the input. I didn't realize that there was still juice in there, even with the thing unplugged. Of course, I have been told I was nuts for grabbing the plug wires in my car when it was running, to see that they were all seated properly. :D

    By the way, I actually laughed out loud at the Gor-Gor reference.
  10. THIS, is why we need to keep posting the warning on these boards. Some kid's gonna buy a vintage tube amp and really hurt himself someday - God forbid. While we're on the subject, the same goes for TVs, and other (insert here) electronics.

    Maybe "current" isn't the right sparky term, but just know there's still "juice" in there.....


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