I'm back - typing one handed, not plastered, possibly a fracture, possibly torn
tendons. Most of the last two weeks has been spent in a drug induced haze, so I
guess I could have made as much sense as usual here. Awaiting a date from
hospital for an MRI scan - wonder if there's any useful bits spare in the
machine!
I've had the ticking electrolytics and the only answer was replacement.
Wirewound resistors can be unreliable in the high values if they crack the
coating, or can suffer corrosion.
Years ago, I worked at a company called Labgear, who at one time made ham gear.
They also made their own wirewound resistors, and had gone for cement coating.
They found that the ham gear ones were unreliable, but the ones used in
commercial 24/7 applications weren't, and the problem was that the cement
coating allowed moisture in, and they got electrolysis. The commercial ones were
constantly warm enough that the moisture didn't get in......
Not sure what Rich means by a 'six pack of 811's'. Is that real beer as opposed
to the usual US stuff that's an 807? (most of which would be better designated a
955!)
I don't know of anyone electrocuted by not having bleeders, although there was a
case many years back of a big (multi MVA 275kV) xfmr having charge left in the
windings after switch off which threw someone across the shop and killed them.
Strangely, that was alleged to have the been the transformer involved in the
Hixon rail crash in the 1960's. Still like 'safety' bleeders as well, but don't
rely on them. Incidentally, I just splashed out on a professional 40kV DC probe
so I can measure HV rather than guessing...........seems worth it from a safety
viewpoint, somehow. A clip lead across the HV during work is a good idea - just
don't forget to remove it afterwards!
73
Peter G3RZP
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