[R-390] Panel meters again

[Drew P. via R-390]

Tisha wrote:
 [snipped]

"... if you know the internal resistance of the existing panel meter you could
make a little circuit that has the same shunt resistance, tap either side
of a resistor in series and run that into an op-amp, zero and span that to
your hearts content and drive a different meter. (even, Gasp! a digital
meter <joke>). Add a little bit of capacitance to the op-amp circuit, make
the thing smooth out the values, etc...

You could steal power from the 6.3 VAC filament supply, run it to a little
rectifier/regulator and mount that on the same board. Maybe even add a
little internal meter LED light. (or a red flashy LED in the corner to show
on peaks, that would be neat)."

[snipped]
 
"Thinking of a DIP-8 Op-amp package, three lead regulator, tiny little
bridge rectifier, a few resistors and caps, two small pots for scaling,
yea, that would be neat. It could be mounted on a breadboard the size of a
50 cent piece."

Someone here did just that some years ago...might check the "Pearls of Wisdom".  IIRC, it was Les Locklear. My preference goes for Dave Wise's modification, not as versatile, but certainly much less work.

Drew