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i may have mentioned that the switch on my late 70s MXR Distortion + had died and i would have to replace it. i got the switch a couple of weeks ago but hadn't had time to deal with it till now. after replacing the switch i was still having problems with the signal cutting in and out, so i went back under the hood and discovered that the white wire (there's 5 wires that connect to the one end of the circuit board) had come loose from the circuit board. after fixing that, things seem to work normally, except that if it's plugged into my amp and i unplug the input plug it buzzes loudly. it's less loud when the pedal is switched off, but always present; it goes away as soon as the plug is back in the input jack. i'm stumped. anyone have any idea what's wrong? as far as i can see all the other wiring is intact; the switch connections, white wire connection to the circuit board, and trace leading from the terminal i soldered the white wire to all appear to be OK on visual examination; and the fact that it works perfectly with both jacks plugged in would seem to indicate that the basic functionality is OK. i suppose i can live with it since it's always on my board...it's never left since i first started doing boards. but i feel weird about it, and worry that it might unexpectedly crap out. why would it buzz only when there's nothing plugged into the input jack? n.b. it's plugged into a 9V wall wart and is the only device running off that supply for test purposes, and i just changed the 9V battery connector-to-9V power cable adapter for a brand new one so it's not a power supply issue. no, i don't have a 9V battery, but i doubt that would make a difference.

Is the input jack that is causing a (presumably) lifted ground buzz a TRS jack that is designed to cut ground when unplugged to save on battery life? My hunch is some ground reference fuckery at play, as you say - not an issue while in use.

If you find yourself in that operational condition often, you could look into a normalling TRS that will shunt signal input to ground when the plug is pulled, but that's probably overkill.

it probably is, since it's old enough to completely pre-date any usage of AC-to-9V power supplies. from my research it was probably made around 1978, and i bought a replacement bottom plate and filed a rounded notch into one side to give the adapter connected to the battery connector a path out of the box. so maybe if i feel like being anal about it i'll try and figure it out. i'm probably not going to get into changing jacks unless i absolutely have to...i don't like soldering in general and am very nervous about doing it on circuit boards, specially this one which is textured cardboard rather than a normal modern board. and the D+ has been the first stage post-tuner on every board i've ever used so it's probably OK as-is. thanks for the input!

My hail-Mary thought would be to take steel wool/a Scotch Brite pad/an emery board to the walls of the pedal facing the jacks and the part of the jacks facing the pedal and tighten the nuts very firmly when reassembling it. Might help.