20-02-2019, 10:55 PM
An AVO 8 in G.W.O is a perfectly good, if somewhat bulky & heavy, multimeter. All you have to remember is that on DC voltage ranges it's resistance is 20000 ohms per volt, which means that it loads the circuit under test more than a DMM, or, for that matter, a Valve Voltmeter, does. This means that the voltage read on an AVO (or any other Analog meter for that matter) will be lower than that shown on a DMM, most of which have i/p resistances of at least 10 Megohms. The readings published in the service data for your R66 were probably taken with an AVO 8 in any case - they may even have used an AVO 7 for this purpose back then, and, IIRC, the i/p resistance of the 7 on DC ranges was only 1000 ohms per volt. Besides all the foregoing, I'm temped to say 'what's wrong with a 20-year old DMM if it's in good working order. Until it developed a not-easily repairable fault, I was using a Fluke 77 which would have been getting on for that age when it failed.
