Switching supply expertise?

From: Dave Dunfield <dave04a_at_dunfield.com>
Date: Sun May 30 17:36:10 2004

At 21:04 30/05/2004 +0100, you wrote:
>> SMPS are always a pain to troubleshoot, and I've always opted to find a
>> replacement. In this case that isn't probably feasible so ---
>They are a pain to troubleshoot, but they're also a part of the classic
>computer, and thus should be repaired and preserved. Why do people seem
>to think that 'classic computer' == 'CPU only'?

Agreed - I could easily put in a PC supply, and I even have a couple from
"slimline" PC's which would probably fit the box - however I want the machine
to be as original as possible.

>> I'd buckshot the components in the switch driver, such as the IC. Sounds
>In a supply of this age, I would not be suprised if the chopper driver
>was discrete transsitors.

It is - the only IC is the Opto-isolator.

Anyway - I found the problem - It was a shorted capacitor on the primary side
of the transformer - what threw me off was it was NOT one of the electrolytics...
There's another one beside it which is just like it, so I think I will replace

Supply works fine now - and so does the entire machine.

(Joy at getting an old Apple clone working somewhat overshadowed by the fact
 that I finally found a Kaypro today!)

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.
Received on Sun May 30 2004 - 17:36:10 BST

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