I posted this purchase in the "What have you bought recently" topic. Old VTVM, apparently complete:


I checked it over a bit, cleaned the switches (filthy!), vacuumed out the spiderwebs, made sure the tubes were well seated. Today I plugged it in, crossed my fingers and powered it up. Tubes lit up, seemed like it might be working: the zero adjustment moved the meter needle.
I couldn't tell if one of the tubes was lit (5692, a 6SN7 clone) because of the getter silver on top, so I took out, checked the heater: it was OK.
I wanted to see what voltage filter capacitor I'd need to replace the old one, so I measured the voltage across it: only a couple hundred mV. WTF???
It gets weirder: next time I put my DMM on the transformer secondary. It showed 560 volts!
So what the hell is going on here? It's a regular little 3-tube VTVM with a small power transformer, so I figured the HV would be in the 150-200 V range. Could the voltage shoot up that high if the rectifier was somehow open circuit? But even that doesn't make sense to me.
This isn't a serious project--yet. It'd be nice to get this working, but I already have 2 working VTVMs, so it's not urgent at all. But it bugs me and I'd like to solve the puzzle.
Analog VOM shows 580 VAC.