[Techman]

Seeing this thread reminded me that I'd got a few Heathkit items like this. So I raked out a couple of old meters that I'd not looked at for a very long time. The one shown below I probably haven't looked inside for several decades. I couldn't remember if there were still batteries inside and nothing happened when I switched it on. When I opened it up there was just a very vintage HP11 fitted, I must have removed the PP3 at some time, probably because I'd found it had started to leak when last checked. I removed the HP11 (C cell), it measured just over half a volt...not bad for a cell that had probably been fitted sometime in the early 70s!

I fitted a couple of batteries and it didn't work. I carefully checked for meter continuity - don't just shove an ohm meter across these meters, as if it wasn't already open circuit, then it would soon become so! The meter was OK, but the unit as a whole still didn't show any signs of life. However, after checking round a few things it gradually came to life all by itself. It seems to work OK, but obviously needs a little calibration, which I didn't bother with due to the batteries I'd temporarily fitted not being new or up to full voltage. I put it back together, but decided not to refit that vintage HP11 cell!

The last picture below shows an older Heathkit VVM that I didn't power up, saving this one for another day. I've got yet another one that when I rediscovered it in the loft several years ago, I found a very badly corroded grid bias type battery inside that probably dated from the late 60s. - that meter was a bit of a mess, but fortunately just to the framework holding the battery.