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My Amp doesn't work upside-down???

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  • My Amp doesn't work upside-down???

    So, I'm checking the bias of my JCM 800 (getting it ready for a friend to buy), and notice that I don't get any sound out of the unit when it's upside-down. Yes, the speaker connection is solid! Without changing a thing, I get sound by turning the amp right-side up. What's going on??? Is some loose connection shorting out? To add to the mystery, when I probe pin 8 on a power tube socket, it seems as if I don't get a reading for the plate voltage. I've probed it before and it should be ~480v.

  • #2
    Re: My Amp doesn't work upside-down???

    i think it must be something is loose and shorting out the circuit and coming in contact with somethin else when your flip it upside down
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    Fender Telecaster 1962 Reissue MIJ
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    • #3
      Re: My Amp doesn't work upside-down???

      Don't tell your friend. He'll probably never turn it on, upsidedown. I dunno. I can only think it's a power, input, or speaker connection that gets broken from gravity pulling a wire the opposite direction. I had a problem with an old Marshall shorting out intermittently. It turned out to be bare wire too close to the chassis, and the wire kept arcing current against the chassis.
      Originally posted by Boogie Bill
      I've got 60 guitars...but 49 trumpets is just...INSANITY! WTF!

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      • #4
        Re: My Amp doesn't work upside-down???

        I should mention that I think I have a phase inverter socket on the way out...(bent pin contact).

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