[The Philpott]

Hi Roger, I am not a guru but i have kicked 3 Model 8's (Mk III) and 2 Model 9's (Mk II) into a reliable state.

The circuit diagram for the Model 8 Mk II or III is to be seen everywhere (there is one on this website, and also probably one on richardsradios, if you don't have the original paper working instructions to refer to)

I am assuming you have a Mk I, II or III, and if so:

The circuit diagram gives you the leaf switch position protocols, and errant clearances (or blackening of the silver) in these switches is a common problem...This is most likely what has happened to your meter. It is sometimes necessary to tweak (ie bend!) one or more of the leaves to return the switch stack to life. (If AVO kept in a box for many years with rubber test leads in a warm environment sulphur can blacken the contacts, for example)

There is also a rotor (with cam lobes) on the back of both rotary selectors, these rotors have occasionally been known to come loose, which then puts the operating cams out of phase with the leaf switches. Doesn't usually happen unless there has been arcing, causing the sliding contacts to jam.

(I assume you mean with a D cell you get Ohms and Ohms divided by 100 to function?)

Please bear in mind i know nothing about Model 8 Mk IV and onwards- and some or all of the above may not apply to them!

Dave P