Another co-incidence you mentioning VTVMs David. Very recently I had a full uphill struggle with a Hewlett-Packard VTVM model 400H; dates from 1961. The fault was that the needle was extremely unstable: either no deflection at all or banging hard against the end stop - with occasional fleeting pauses at all points in between. One very strange symptom was that the entire chassis was 'hot': just a touch on any part of the metalwork - no matter how gentle the touch - and off it would go. (Yes, the mains earthing was 100% intact - as was the 'cold' end of the input wiring - which was joined direct to chassis.) A 'scope on it showed that it wasn't going unstable - which looked favourite; the fault was partly due to badly seating valves. So I replaced two valve sockets which effected some improvement - but it soon became apparent that all of the eight sockets (B7G and one B9A) would have to be replaced as well! 
And they were riveted to the chassis. At that point, after having changed several R and C, and having spent several days on it (I don't give in easily) - I called "time up": it simply wasn't any more effort. I only started to look at it because it had been hanging around in my 'to do' pile for about 4 years and was getting in the way. And I was unlikely to ever seriously use it: I use a 'scope for such measurement. So it was dismantled for salvage spares - which included a very nice mains transformer and a 2 uF 400-v non-polarised capacitor that I know I'll need to repair my HP 1715A 'scope! 
Having said all that, one day I might just get around to designing and building my own VTVM based on F.E.T.s.: a much smaller unit, battery-powered and much more versatile - and stable. When - and if I do - the GVR will be the first to see it! But don't hold your breath folks!
Al.
And they were riveted to the chassis. At that point, after having changed several R and C, and having spent several days on it (I don't give in easily) - I called "time up": it simply wasn't any more effort. I only started to look at it because it had been hanging around in my 'to do' pile for about 4 years and was getting in the way. And I was unlikely to ever seriously use it: I use a 'scope for such measurement. So it was dismantled for salvage spares - which included a very nice mains transformer and a 2 uF 400-v non-polarised capacitor that I know I'll need to repair my HP 1715A 'scope! Having said all that, one day I might just get around to designing and building my own VTVM based on F.E.T.s.: a much smaller unit, battery-powered and much more versatile - and stable. When - and if I do - the GVR will be the first to see it! But don't hold your breath folks!
Al.
