[Craig Sawyers]

I bought mine from Gerry Horrox for a hundred quid with a know dead meter. But I found the AVO MkIV test meter (basically a VVM) had physically the same meter - and I was given it free. So I sacrificed it for the meter, swapped scales, and implemented the op-amp fix to compensate for the very different sensitivity meter.

Then I changed a resistor value so the default range is 100mA FSD with the current controls set to zero. So you get a value for the anode current with a specified grid voltage. Plus the opamp limits the voltage on the meter, so it overloads by an absolute maximum of a factor of two even if you get the settings entirely wrong.

So it is pretty bulletproof now and works perfectly.

But usually bidding goes potty for an AVO valve tester. I cannot get my head around the price people are prepared to pay for an operationally unknown tester.

I was lucky to be given my MkIII and MkII valve testers free. The MkIII needed a new Vg pot - fortunately linear in the III. And the MkII had a stuffed meter - but an electrically dead (but living meter) MkIV VVM has yielded yet another compatible movement, currently awaiting an op-amp fix.

Craig