Switching supply expertise?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun May 30 19:33:59 2004

> >> 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.

What, not even a TL431 in the secondary-side regulator? That does suprise me.

>
> Anyway - I found the problem - It was a shorted capacitor on the primary side

Well done!

> 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
> both.

Maybe part of the snubber network on the primary of the chopper
transformer. In which case, check the associated diodes too.

>
> 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!)

I really must find a CP/M luggable sometime....

-tony
Received on Sun May 30 2004 - 19:33:59 BST