Cossor 1044K Valve Voltmeter.

[Yorkie]

Just a small snippet of trivia - but relevant to this thread.

Many, many years ago (early 1970's) I had a good friend who was a highly skilled and, it must be said, a very gifted electronics engineer. He designed a whole raft of electronic equipment for his own hobby use and some of it was quite impressive too. Anyway, the only multimeter he ever owned & used was a Heathtkit VTVM. I'll never forget the way he used to gently tap the meter transparent plastic cover now and again, because the needle would occasionally stick!   I never did discover if he cleared that minor, but irritating, fault.

Al.

I had one for a number of years, with the same apparently defective meter. I was lucky enough to get a brand new boxed meter movement for just £3.00 at a rally at which Heahtkit UK spares were being sold off. I fitted the new movement and it had exactly the same problem. I later discovered that it wasn't the meter itself, but the clear plastic front that was the culprit. Static built up and caused the meter needle to freeze. Take the front off and all was well. I used to just wet my finger and thumb and put them on the dial and to the case, and it removed the static. It was most likely that tapping the plastic cover would have the same effect in removing the static.

A valve Voltmeter, with an input impedance of several MegOhms, is far superior to an AVO, which - though better made - at 20,000 OPV, is no better in terms of accuracy than many cheapo analogue meters which generally have 20,000 OPV input (assuming it's stated, which it often isn't). Fine, if users know the limitations and in what circumstances the AVO will load the circuit under test, but I suspect that many don't. Extremely well made, designed and built, jolly expensive in their day, and the standard instrument quoted on many radio and TV service sheets. Nice to have on display on the shelf, but of limited use on the workbench IMHO. AVOs and DAC90As deserve each other, but time has moved on. Certain names - AVO, Fluke and TEK come to mind - seem to create in the minds of some, an almost evangelical appeal. Avo is to multimeters what Thermos is to vacuum flasks, and Hoover is to vacuum cleaners. All have become genenric terms.