Tube Works Real Tube Schematic

[Blues Lyne]

This isn't really build question. I've got a real tube that makes no sound on or off except for a loud dreadful buzzy hum.  Really loud.  I suspected a ground problem.  When I conected the leads of my multimeter between the grounded lugs on the input and output jacks the hum stopped.  I connected a wire between the two and have sound now, but since there was never a wire connecting the two, the problem must be elsewhere, so I thought if I could find a schematic I could maybe fix the real problem rather than just riggin' it to work.  Any suggestions where to look would also be appreciated.

Thanks,

Blues

[Peter Snowberg]

Welcome to the forum Blues.

I suspect that you did have a ground problem but it's now fixed.

Sometimes makers go the cheap route and leave off gorund wires that should be there, relying on chassis ground instead. This is really bad in the case of aluminum because it has microscopic coating of aluminum oxide on the surface from moisture in the air. All it takes is a little oxidation and/or a nut to loosen up and suddenly you have buzz and no effect.

[puretube]

have you changed anything related to the mechanical parts of the chassis?
(like different in/out jacks?)...
or moved the circuit out of the box?

[Blues Lyne]

Thanks for the replies.  At first I thought the jacks were grounding via the chasis, but this doesn't appear to be the case.  The chasis is painted and neither jack shows continuity to the chasis when tested with my meter.  I haven't changed anything structurally.  I put a different tube in it, but that was long (years) before this problem started.