What a lovely old meter! Japanese? As used by technicians during WW2? It's essentially a 1mA meter with series resistors selected by the voltage range switch, so that at the full scale voltage, 1mA of current flows thru the meter. As a result, it doesn't have a fixed input resistance like a modern digital meter. It has a sensitivity of 1000 ohms per volt. That is, the resistance on the 10V scale is 10K. On the 100V scale, 100K, etc. There were more expensive meters with 100uA movements, but they were too delicate for field work. Anyhow, there is usually a fuse inside the box, and that is usually why old VOMs don't work. Finding a fuse to fit a gadget from Japan 3/4 of a century ago may be impossible.
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As for the mic, tracing SMT circuits is not easy. I haven't seen an NT1A myself, so I'm looking at your photos and the circuit as found on the WWW. What to do when the culprit is found may be interesting. If the capsule is leaky, try cleaning around the edges? Add an input capacitor and another 1G resistor between the capsule and the FET? That way, a small leak at the capsule won't upset the circuit, but the mic won't be "as designed" any more, and the capsule may turn out to be noisy. If the culprit turns out to be a component on the PCB, obtaining a two-penny part and replacing it will be a nuisance, but the process is instructive.
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If the rest of y'all are getting bored, we can take this thread private.
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