Quote:
Originally Posted by David G4EBT
... Yes, they say it's 'metal loaded' but it depends on one's definition of 'loaded'.
Before ever I used if for such purposes as re-fixing valve bases and re-stuffing capacitors, I applied 'Super Steel' to a strip of glass 50mm long x 15mm wide, then tested it on my Victor V60B insulation tester at 1,000V ...
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Thanks for that. It's interesting (and also good to see the trouble being taken to check before getting started
). Clearly there isn't enough metal in that stuff to make a continuous conductive path through it. So that just leaves the question of breakdown strength. Since the croc clips aren't at the ends of the glass perhaps the 1000V was applied over 33mm (makes the sums easy
) ? That would put the test field at 30V/mm, which the glue withstands.
I rooted out an old IO base and sacrificed a bit of mm graph paper and I reckon that the peened-over metal on adjacent pins is about 3mm apart. In a cathode-biased EL34 the adjacent anode and heater pins, or screen grid and control grid pins might (worst case, I admit) be 450V apart. The field would then be 150V/mm. If you still have the bit of epoxy-coated glass it would be interesting to know whether it's fine with a 1000V test and the croc clips 7mm apart. It would also be interesting to know whether temperature changes anything, but now this is becoming a student project
!
EDIT: What made me think of this was a post on here a few years back from someone who had tried a metal-loaded epoxy as a base glue and found that he was getting a breakdown problem. I can remember who it was (at least his real name, if not his current username) but I can't track down the post right now.
Cheers,
GJ