On Sat, 20 Feb 1999 22:47:52 -0800 Rich Measures <email@example.com>
>>On Sat, 20 Feb 1999 05:43:15 -0800 Rich Measures <firstname.lastname@example.org>
>>>> Last time I did this I used a piece of an old
>>>>fiberglass fishing rod (the large end) and ran
>>>>it through the resistors leaving about 3/4" extending
>>>>on each end and then clamped the ends onto standoffs.
>>>> On just about every alpha 77 I've worked on I've found
>>>>some arc damage from the bleeders to the mounting bolts,
>>>>don't like that method.
>>>Ä Good point. Through-bolt mtg. also blocks cooling air.
>>Not if done by the mfgs book.
>? Through-bolts require some sort of shouldered insulating washer at
>each end. this tends to block air from moving through the inside.
Yes of course but if run at or below rated wattage it will survive.
>>>100k wirewound resistors are known to have a high failure rate.
>? Virtually all of the open failures I have seen or heard about have
>been in high-values. Perhaps because the wire used is extremely fine.
Which is why 100K is the suggested max in any literature I have seen for
bleeders. It also helps to not try and run them at the absolute limit
just to save a few bucks.
I run a pair of 100K 200W in my 2M 4KV supply, runs cool.
>>>If I wanted a Reliable bleeder for a 4kV C-filter supply, I would
>8 to 10
>>>Matsushita/Panasonic 100k-ohm, 3w MOF resistors on a piece of
>>>perfboard and be done with it.
>>Absolute YUK ! 800K to 1M bleders..no way Jose.
>? What is to be gained by using a 200k-ohm bleeder on a C-filter,
Quicker HV bleed down time, less chance of a recharge. All my concerns
are safety related and for others not well versed in PS issues.
A string of 3W does not offer much of a voltage breakdown safety margin.
Matsushita not a common distributor item and similar wattage Panasonic,
etc are only 350V. Going to a 1KV rated Philips AC-03 resistor gives a
comfortable safety margin if such a string is preferred.
73 Carl KM1H
>R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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