The SCH-5000 is unique and not very similar to other "similar looking" HV
modules. It uses fused metal-oxide encapsulated (hermetically sealed)
rectifiers having a .060" circular die metallurgically bonded to solid silver
leads, and the leads are welded with the corners rounded (to prevent corona
inception) prior to vacuum potting with a very good thermally conductive epoxy,
Emerson-Cuming 2650FT. All the diodes are closely matched for breakdown
voltage prior to assembly and welding, and the finished assemblies are X-rayed.
The diodes themselves have very low leakage, way below specification (normal
spec was 1 uA at 5000V, but diodes were tested to be about one-tenth that) and
they're all high temp avalanche devices that can handle a lot of avalanche
energy if needed.
Ratings aren't particularly high, but "burned in" versions of exactly these
same assemblies are used in missile systems, jet engine exciters, and many
defense/aerospace applications all over the world since the 1970s. I wouldn't
compare them with much "off the shelf" stuff.
-WB2WIK
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Paul Christensen
Sent: Thursday, October 16, 2014 1:15 PM
To: Amplifier Mailing List
Subject: Re: [Amps] HV Diodes
Manfed,
Regarding Alpha, the 77Sx (dual 8877) uses a quad set of Semtech SCH5000
modules rated at only 5KV/0.5A. The current rating is increased to 1A with
forced-air cooling. I¹m sure these have failed owners at one time or another
but they seem to have held up well for most 77/70 amp owners. If mine ever
blow, they¹ll get upgraded to slightly better specs at that time but nothing
greater than the equivalent of six 1N5408 types per leg.
I¹m all for ³super-sizing² components, but not until a circuit¹s minimum
safe limits are calculated. Over-sizing for the sake of over-sizing
seems like a lazy way to impress friends!
Paul, W9AC
-----Original Message-----
From: Manfred Mornhinweg <manfred@ludens.cl>
Date: Thursday, October 16, 2014 at 3:47 PM
To: Amplifier Mailing List <amps@contesting.com>
Subject: Re: [Amps] HV Diodes
Carl,
> Suffice it to say that the real world of tube type ham amps uses the
1N5408
> almost universally no matter what the configuration.
Do the Alpha 8410, 9500, 8406, and the 89 belong into the real world of tube
type ham amps? I would say, they do. And they don't use the 1N5408 but instead
use a potted bridge rectifier, rated at 5kV peak inverse voltage and 2A total
forward current. I don't know with certainty what's inside it, but 4 strings of
5 each 1N4007 diodes would have exactly those ratings. Instead a bridge made
from 1N5408 diodes would have a rating of 6A total.
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