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Re: [Amps] GS35b FWB issue]

To: amps <>
Subject: Re: [Amps] GS35b FWB issue]
From: Ron Youvan <>
Date: Mon, 11 Jul 2011 14:39:59 -0400
List-post: <">>
Steve Thompson wrote:

>> I have checked everything else in the PS, and the common
>> denominator seems to be the cap bank.  Am I missing something?

> Fuses between the transformer secondary and the bridge :-)

> To kill diodes in that way, you've got to be looking at something
> approaching a short - it's hard to see how loose screws would
> cause that. Open cct bleeder resistor(s) might, if one cap arcing
> led to over voltage on another and so on.

> Another thing to check is the insulation between secondary and
> core on the transformer. If one end arcs to the core you can end
> up with one leg of the bridge 'shorting' out the secondary. If
> that's  happening, then I think your damaged diodes will always be
> in the legs feeding the -ve end of the caps.

   I have been puzzling over this, I think it is either something that is not 
on the schematic (like 
a terminal strip or mounting screw arcing) or the secondary winding is arcing 
to something, you need 
to "hi-pot" the transformer's secondary winding to the frame and the primary 
winding/s for 10 or 12 
kV before you cook more diodes.
    Ron  KA4INM - A city is a large community where people
                  are lonesome together -- Herbert Prochnow
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