That is an easy assembly to fix yourself Kathy. However why did they blow?
The usual cause is old original and leaking filter caps. Another possibility
is a run away parasitic condition that exceeds the diode ratings before the
internal breakers pop.
For repair you can use 1N4007's or go a step up to 1N5408's which will
require the mounting holes to be drilled out a bit.
Those mounting style caps are no longer available except as high priced
speciality items. The common Snap-In cap in 105*C rating can be adapted with
a little work or if you are really creative you can restuff the old cans
with them.
Also replace those heat generating equalizer resistors with 100K 3-5W metal
oxide.
All done the PS will last another ~40 years and you can be proud of doing
it.
Carl
KM1H
----- Original Message -----
From: "Kathy Bookmiller" <wb2aio@yahoo.com>
To: <amps@contesting.com>
Sent: Thursday, March 24, 2011 11:46 AM
Subject: [Amps] SB 200 blown diodes in power supply
>I know many of you probably consider a SB200 as a driver for your real
>amps, but for us QRPers, it is as good as it gets:)
> I just blew a diode in HV chain. Now one friend I respect says I should
> put in the Harbough board, soft start, etc. Trouble is, that's money I
> don't wish to spend if I don't have to. Put in new board is easy to say
> when you have money, but us poor underpaid nurses....
> Taking a look at mine, I noticed there are 3 diodes already replaced in
> the two strings by placing them under neath or on the bottom of the board.
> When I first looked at it, I thought they had been vaporized:), so this
> isn't a new problem.
> I'm hoping to find something at Radio Shack I could use and just change
> out the newly blown diode, maybe even using the trick the previous owner
> employed of just putting in the new one underneath to save taking it apart
> to get at the top of the board.
> So was wondering what you guys think or your experiences with the SB200. I
> just acquired it last summer and otherwise has worked really well when
> I've needed it.
> 73,
> Kathy, RN
>
>
>
>
>
>
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