Mandobird pickup hum-Bad ground?

[Mandodork]

I've had a mandobird for quite some time with no issues. Plugged it in the other day and had loud hum from amp. Tried different cords and amps, no change.

Touched one of the screws on the back cover plate and the hum stopped. Looked inside and didn't see any obvious shorts.
Left the screw out and it's OK but wonder what the heck happened.

Only noteworthy change is it's been much more humid here lately.

Thoughts? Theories?
Thanks.

[rockies]

I always look for simplest first, it does sound like a ground problem, not a short but an open or poor connection. The most logical is the part that gets the most use and movement .. the output jack. Check it out for broken wire, loose nut etc etc. Inexpensive jacks sometimes the crimping that holds the threaded part on gets loose andcauses an open ground. If that is OK start checking grounding of all parts for loose nuuts, screws, solder connections. do it with guitar plugged in, you may move the part with the problem to show you where to look.
Dave

[mandroid]

Metal foil lined body cavity and the underside of the scratch plate?

[Mandodork]

Yes, the scratch plate is foil covered, but not the inside of cavity.
Still curious why touching/removing the one screw stopped the hum.

[rockies]

We should look at this logically ... mandobird worked properly, then something failed !causing a hum problem. Most lkely scenario is a ground connection failed. This probably caused a ground loop situation. Removing a screw probably removed another ground (possibly the foil ground) breaking the ground loop. Put the srew back inn, making it hum then search for the original ground failure, probably in the output jack as a start, then carefully check grounds in the control cavity, pots, pickups etc etc. It worked before so no use thinking about cavity shielding and stuff...it worked before so something failed. Good luck !!
Dave