So I bought a high voltage probe on ebay, RCA brand, and I noticed that when I took it apart it smelled kinda funky. I believe it is made in the 1950's but there is no model number or anything like that.
I don't think that PCB's smell bad, but the bad smell made me feel kinda anxious. How safe are plastics from the 1950's? How about the wire on this probe?
Should I just avoid this 1950's shit?
This probe has some soft plastics in it, as I understand it hard plastics are OK but soft plastics = bad. Should I just take the 1 gigaohm resistor and toss it?
My heathkit HV probe has no soft plastics in it..
The "hard plastics OK,soft plastics,bad" rule is not very useful.
PTFE is a "soft" plastic,as is Nylon,& both have good insulating properties (although Nylon isn't too happy with RF).
All the EHT probes I have seen from the 1950s/60s use a large conical shaped moulding made of hard Polystyrene,with a metal tip on one end,a high voltage 1000M Ohm resistor inside this cone,which then connects to the lead to the meter.
Hard Polystyrene has good insulating properties,& maintains them over a very long time,if it is not exposed
to ultra-violet light,weathering,etc.
I've never seen one of the high value resistors with anything wrong with it except physical damage.
In service,these probes may only clock up a few hours a year,so they are not in service continually,as is usually the case with resistors changing in value.
Another point is that the probe may not have been designed for use with the kind of meter you have.
For instance,at my old work,we had some Electrostatic voltmeters which used very similar probes,but may have had very different input impedances to a modern DMM.
If it is useable,I would sooner trust an old unit made by a reputable company in Australia,the USA,the UK.or Germany,etc,than some crud modern thing made in the PRC.
These were not cheap units originally,& would,in most cases been "babied" throughout their service life with the original company.