[Amps] Strange power supply

[Barrie Smith]

It's a bridge, with four "Silicon Alley" diode stacks.
----- Original Message ----- 
From: "Peter Voelpel" <df3kv at t-online.de>
To: "'Barrie Smith'" <barrie at centric.net>; <amps at contesting.com>
Sent: Wednesday, April 19, 2006 7:22 PM
Subject: RE: [Amps] Strange power supply


> Sounds that you lost a diode string.
> Is that a rectifier bridge or a doubler circuit?
>
>
> 73
> Peter
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Barrie Smith
> Sent: Donnerstag, 20. April 2006 02:52
> To: amps at contesting.com
> Subject: [Amps] Strange power supply
>
> I recently boxed-in my all-purpose power supply with thin panels of wood, 
> in
> order to protect the cats, and run my 432 amp.
>
> Just prior to the box-in, I ran my 8877 6M amp at 4200 volts idle, and 
> 3800
> volts at 1 amp load with no problems.
>
> Now, attached to my 432 amp (2 X 3CPX800), running 3000 volts idle, 
> results
> in 2000 volts under 1 amp load.
>
> I've run this amp on the same power supply in the past with no problems,
> although it's been awhile.
>
> I've taken the panels off, thinking that I've screwed something up, but 
> the
> results are the same.
>
> Under a 1 amp load I'm also hearing a (60 cycle?) loud hum, that increases
> in volume as the loading is increased.  I've never heard the hum in the
> past, even when running the 6M 8877 amp at above ratings.
>
> This is not a whimpy power supply.  It has a 2 amp, 5000 volt Peter Dahl
> transformer, with a 30 amp variac.
>
> Before I start throwing parts all over the room, does anyone have a clue 
> as
> to what I may have going on here?
>
> 73, Barrie, W7ALW
>
> I've cleaned the step-start relays, which are each 25 amp, and put contact
> cleaner on the variac.
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