30 May
2008
30 May
'08
7:48 a.m.
Hi
First, I agree with Tony, the transformer is most likelty OK. Your
earlier description wouldn't be enough to say it was good or bad.
Measuring things on the primary side with a scope would be difficult
without using an isolation trasnsformer. The point in the circuit
that you'd need to use as ground reference has about 150-170
volts DC on it. If you connected the scope ground to this point
you'd really blow things without using an isolation transformer.
Next is that T3 is a pulse transformer and not an 60Hz AC transformer.
The input is from the regulator chip, pins 8 and 11. One should
see a 50-150KHz pulse on these pins.
This would be the first place I'd look.
Dwight
From: javickers at solutionengineers.com
To: cctalk at classiccmp.org
Date: Thu, 29 May 2008 20:56:53 +0100
Subject: RE: Transformer repairs
Dwight Elvey wrote:
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Hi Ade
If it is a switcher, it sounds like you don't understand how
these work.
You're right, I don't; although I'm getting a better idea.
Please send a pointer to the schematic you
located. We can
then talk about failures in switchers.
The schematic is available in this document:
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/sx-64/sx64sc
hematics.zip
(that's a 19.7mb download)
The PSU info starts on P25 of the PDF, and the schematic is on P28 (2nd to
last).
OK, let's talk failures ;) If you've got any links which give a sensible
description of how a switcher works, I'd be most grateful.
Cheers,
Ade.
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