Ice-Tea

All as you describe. Also: Measured the (new) switch. Center lug is connected to both outer lugs in the center position. So: switch is good. Volume pots work respectively on rythem and treble settings of the switch. Both pickups work on their respective switch positions. Doesn't leave a lot of unknowns, does it? I'll take her to the lab tomorrow and hook her up to an oscilloscope and see what happens.

Short youtube vid capturing behaviour Note1: no, I haven't checked if the switch is upside down, so that's a 50% chance for you Note2: yes, my friend is a leftie. No, I'm not the friend in question.

Thanks for the (mostly) kind pointers Yeah, I was missing the pickup from my mental image. In addition, I must have had the selector switch in the mid position for some of these measurements. When disconnecting the switch from the rest I get readings between zero (makes sense) to 140k or so (makes sense) to 13.8k (ie the pickup dc resistance. So far so good. The reason I'm poking around in the first place is because the selector switch doesn't function the way I thought or think it should. Ie: when the selector switch is on rythem the neck volume control knob controls the volume (bridge does nothing). When the selector switch is on treble the bridge volume control know works (neck does nothing). But in the middle position I was expecting both to work but only the bridge pickup and its volume control work. So I obviously figured bad switch and replaced it but it's still the same.

Hello all, Long time amateur guitartis and long time not so amateur electronics engineer here but to be honnest I'm a bit lost with a Les Paul a friend gave to me to check out. It does some weird things with the volume pots. When measuring resistance between the signal from the pickup and the connection to the switch on the pots, it would go from zero to, say, 150k and then hover there or even go down again (rather than to make it to 500k as I was expecting. I first thought it would simply be a bad pot but it does so on both. I've learned to be suspicious of such things. If one thing seemingly broke then that's a good explanation. If two things seemingly brake you're probably at fault. So, did I miss something obvious?