>
>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.
Wire-wound, high-ohm resistors are unreliable without corrosion and
without cracking due to frangible nature of the fine wire used in making
them, and due to frequent heat-cycling in ham radio service. MOF
resistors are more reliable.
>
>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......
>
Amen
>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?
"811s" are larger glass bottles. Real beer comes from Deutchland and the
Emerald Isle.
> (most of which would be better designated a 955!)
>
Chortle
>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!
>
Amen to that. A local repairman was recently killed when some schmuck
switched on the mains breaker while he was doing repairs. A shorting
device would have saved his life.
>
cheers, Peter
- R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|