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

[mrid]

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.

[flank]

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

[Gearjoneser]

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.

[mrid]

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).