UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Comark Early 1905 Insulation Meter Checks

Bazz4CQJ · 23rd Jan 2019, 12:29 am

Many thanks for that Jim. I'll try and find a few minutes to plot the numbers.

As the owner of an Avo VCM which has one dodgy 50uA meter (needs a corrective op-amp to drive it), it does seem as if Comark used some better quality meters, as they seem to be surviving better than many of the Avo ones.

Is the use of the usual pair of "side by side" silicon signal diodes (or maybe Schotky's?) across the meter likely to offer useful protection?

I don't use my 1905 very often, but it is one of those instruments which (having paid 50p or £1 for it at a rally) I feel is very nice to have around. I also have an old analogue Comark thermocouple meter (similar size and style) which has proved very reliable and useful, and that too was picked up at a rally for next to nothing.

B

23rd Jan 2019, 12:29 am	#13
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	Re: Comark Early 1905 Insulation Meter Checks Many thanks for that Jim. I'll try and find a few minutes to plot the numbers. As the owner of an Avo VCM which has one dodgy 50uA meter (needs a corrective op-amp to drive it), it does seem as if Comark used some better quality meters, as they seem to be surviving better than many of the Avo ones. Is the use of the usual pair of "side by side" silicon signal diodes (or maybe Schotky's?) across the meter likely to offer useful protection? I don't use my 1905 very often, but it is one of those instruments which (having paid 50p or £1 for it at a rally) I feel is very nice to have around. I also have an old analogue Comark thermocouple meter (similar size and style) which has proved very reliable and useful, and that too was picked up at a rally for next to nothing. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.