Gas test - AVO VCM mk 1

[Robert Darwent]

In all the time I have owned and used my valve tester I dont beleive that I have performed a gas test on a valve. Does anyone know how to do this and at what point the gas button can pressed during the testing cycle?

I've an AVO VCM Mk.I too and I don't think I've ever pressed the 'Gas' test button on an actual valve I was testing either!

However, according to the Mk. I operating manual the instructions for carrying out the 'Gas' test are given on page 20, specifically paragraph 7 which states;

"7. Where a valve is suspected of passing too much grid current, a measure of the magnitude of grid current at the desired conditions of applied electrode voltage may be made after having measured the mutual conductance of the valve in question. After having set the valve up and backed off the anode current to zero as for mA/V test, the button maked 'Gas' should be pressed. Any grid current flowing will set up a DC grid voltage across the 100,000 ohm resistance introduced into circuit."

If you haven't got a copy of the op manual I can post a pdf copy to this thread if you like?

Regards