Uh, sri but the "tropenfest" is actually a hamfest located in the tropics (or
within an "en" of the trop--ics).
Charles Harpole k4vud@hotmail.com
> From: la7sl@norgespost.no
> To: amps@contesting.com
> Date: Mon, 8 Feb 2010 13:52:36 +0100
> Subject: [Amps] best choice HV caps..if you can find them
>
> The best choice you can make when it comes to HV filter caps
> are the MP types. These are made from either metalized paper (old types)
> or some sort of metalized plastic foil stacked or rolled up to proper size.
> These units are not small ! But they are (most of them ) self repairing !
> This means that if you get an internal breakdown/flashthrough they will just
> burn away part of the metalization around the burnt hole in the foil on the
> next
> restart. The result is a capacitor with a very slight capacity reduction.
> To do this you need a transformer/ rectifier combination with a low internal
> resistance to be abble to supply the necessary "burn" current. Most good
> PSU designs will handle this. (disengage soft start in this case..)
> In service the stored energy in the cap is usually sufficient to do the
> "burn" immediately
> on fault...and all you will notice is a little power " glitch" unless you
> have very fast
> protection circuits.
> I have two of these units marked "Bosch MP " in an old homebrew amp i made
> here a long time ago.
> They are 4500V 8uF units. Cylindrical metal cans abt. 12 inces long and 4
> inches in dia !!!
> Fitted with HV ceramic connectors. Also marked "tropenfest" ---meaning rated
> for
> tropical conditions in temp and humidity.... They are virtually
> indestructible !
> If you ever come across something like this : Grab them and keep them !! They
> are pure gold for
> any HV PSU builder !
> Peter
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