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Here's how I did it

Posted by Triode_Kingdom on December 2, 2024 at 10:51:12:

I used a 1mA meter with a shunt for full scale deflection of 100mA. The small shunt resistance diverts nearly all the cathode current around the meter. I also fused the cathode and added a Zener to prevent cathode voltage from going too high if the fuse opens.

In my case, the meter measured 90Ω. The formula for the shunt is:
Shunt R = Meter R divided by (n - 1) where n is the multiplier.
Note that high sensitivity meters can be damaged if you attempt to measure them directly with a VOM or DMM. For example, my DMM outputs about 0.5V on the "non-diode" scales. That would result in an over-current of more than 5mA with the panel meter I used. Here's how it needs to be done:

To answer your question more directly, the meter is mounted on the front panel in my monos, and I leave it active all the time. It's reassuring to know the output stage is operating as intended. :)