This is really getting off topic, but if you would like to reduce the
zero drift of your VTVM - any make or model - change the tube to a
6FQ7. You will have to rewire the filament connection but that's
minor. The 6FQ7 is pin-for-pin replacement for the 12A* series and is
far more stable over time. It was designed as an RC type horizontal
oscillator in the old tube type TV sets and stability was a prime
consideration.
It is about a half inch taller than the 12A* tubes, so that may be a problem.
I've modded all my VTVMs with it and they work much better.
73, Bill W6WRT
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