"raypsi" wrote in message
...
I'm building a VTVM based on a BK Precision model 177I'm..

I have a 50uamp meter from a kirby flyback tester.

I'm gutting the kirby it has a 6w6gta tube I'm not going to use the 6w6.

Using a 12sn7gt dual triode instead of a 12au7 so I can make use of the
existing tube socket in the kirby.

and a string of resistors to get to 11meg ohms 1%


I'll read the control grid, screen grid and plate currents, and HV on the
15 volt scale only.

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.

tyvm in advance
de n8zu


You pay attention to what you are doing so that does not hapen.

One other way to protect meters is to place a pair of diodes back to back
across the meter. Not sure what the voltage would be across the meter in
what you are building. The diodes will conduct at about .6 volts if silicon
and .3 if germanium.