Quote:
Originally Posted by WME_bill
D75. Leakage across the high voltage terminals of the EHT transformer.
MotorBikeLes is quite right. There was some discussion about this fault in 2013 and also a bit earlier.
I posted the cure I have used since several times in April 2013 is to use a standoff insulator or a TV tuner ceramic feed through capacitor to make a new well insulated terminal. Reduces the risk of the wire breaking off as you try to re-insulate the paxolin panel. Search under Telequipment D83 EHT.
If you want to do it the hard way, a blob of Araldite will insulate quite well or I have also used Tensol 70, the perspex cement, even better.
You will soon be wanting to measure the high voltages. This keeps coming up. See postings of November 2011 (under D83) and more recently of October 2013 upon making a high voltage probe for EHT supplies, and is simple provided you re-calibrate each time.
wme_bill.
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Thank you, nice hint. I did not think of ceramic feed through capacitors. However, I am not sure if something like
this would work. At the soldering post which I observed arcing at, the coronary discharge jumped at least 1mm farther than the insulation distance of these capacitors. It may be that this was just possible due to surface creepage on the somewhat conductive surface of the old insulation lacquer. I found HV clearance computations on the web that suggest between 10mm and 15mm of clearance between 2.5kV conductors which could not be achieved just by using feed through capacitors or my ceramic sleeves. This is the reason, I am suspecting that I need some extra insulation lacquer. The issue with epoxy based two-component glues like Araldite (or something like UHU Endfest 300 here in Germany) is that I am not able to find specifications on their electrical insulation or moisture absorbance properties. This would be important, since once you put this stuff on, it cannot be removed anymore and could potentially ruin everything. The best solution would maybe an insulation lacquer that hardens into a brittle state, so it can be removed mechanically.
For measuring high voltages, I have acquired a HV-probe for 10MOhm DMMs.