I forgot to ask
5) Does DCV work properly?
a) If you short the probes, do you get 0.000V?
b) If you measure a 9V battery, do you get roughly 9V?
5a) Yes.
5b) Yes. Compared to a cheap Mastercraft (Canadian Tire store house brand -- made somewhere in China) autoranging meter, the two agree within 0.005volts @ 1.5 VDC and within 0.03 volts at 31 VDC from my bench power supply. On a fresh 9v battery, they are within 0.02 volts. No difference if I swap the probes from one meter to the other or exchange + and -.
6) Does resistance work properly?
a) If you short the probes, do you get a stable and steady 0.2 ohms?
b) If you measure a 1k ohm resistor, do you get a stable and steady 1k ohm reading?
6a) No. That's the problem. At the moment shorting the probes starts off at about 24 ohms and slowly (over +/- 30 seconds) drops to stabilize at 19.4 ohms. Next time I turn it on, it might read 40 or 50 ohms. I've seen it read as high as 140 ohms with the leads shorted.
One other oddity: when it's behaving (ie: immediately after dissassembly) open leads will show "OL" on Mohm scale. When it's acting up, open leads will show a high, but not infinite, floating value (at the moment, floating from 48 to 54 Mohm).
6b) No. At the moment a 1 ohm resistor is reading 20.4 ohms, and again, it took about 30 seconds of slowly dropping to stabilize at that. (The cheap meter shows 1.1 ohms, rising from 0 within 2- 3 seconds.) A 1Kohm 1% resistor (1.000 Kohm on the cheap meter, 1.005Kohm on a Karl Heinze type component tester) reads 1.087Kohms when shorting the leads produces .091Kohms (manual range selected).
I'll try the alcohol bath. PTC? As in a thermistor?