In article ,
raypsi wrote:

Only trouble I see is how does one protect the meter needle from bending?
If there is a plate current surge, a glitch resistor might save the rest of
the electronics but if the VTVM gets hit with 150vdc on the 15vdc scale It
will rap the needle a few times around the end post.

N8ZU-

Two thoughts:

1. The VTVM may work with a less sensitive meter movement. You could
connect a resistor in parallel to lower its sensitivity. Perhaps one
milliamp full scale would work?? (Another approach might be to use a
current sampling resistor in place of the meter. You would connect a
series resistor to the meter movement making it a voltmeter reading
voltage drop in the current sampling resistor.)

2. I think one side of the tube would go into saturation, and the other
side into cut-off at some point. Then meter current would be limited by
plate and cathode resistors. In other words, it is a non-linear circuit
when you over-drive it. You may not have as big a problem as you think.

Fred
K4DII