Working voltage for MOX HV resistors

[ohohyodafarted]

Originally Posted by dtvmcdonald

My CT100 has those spiral IRC resistors. I measured them, as well as
the same kind of resistors in all my HV probes. ALL were still
within 1% of the rated value. I useed large numbers back in the 60's and 70s
for science stuff, and they never failed or drifted.

Obviously, too much voltage could overheat them, or
one could arc to the chassis ... and this could destroy them.

I agree, and in fact I found evidence of where there was indeed arc over to the chassis on the set I am working on.

Additionally one also needs to consider how old these resistors are, and what kind of environmental factors they may been subjected to over 60 plus years. Just because these types of HV resistors were reliable when new, does not necessarily hold after many years of potential adverse environmental factors.

There is also a fair amount of surface corrosion on the chassis of this set, indicating that it was in a humid or damp environment at some point.