Commodore Superpet video problem -- ideas? - test-drb@ccmp.vtda.org

1 Feb 2013

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  From: Robert Ferguson <rob at bitscience.ca>
 Subject: Commodore Superpet video problem -- ideas?
 To: cctech at classiccmp.org
 Date: Thursday, January 31, 2013, 3:07 PM

 Hi folks,

 I'm having intermittent problems with my Superpet. It will
 run fine for some time, but then will "glitch" for a couple
 of seconds (including video distortion), and then hang. 

 Having done a bit of digging, I suspect that the flyback
 transformer is arcing internally. The video board is the one
 in this schematic (http://zimmers.net/anonftp/pub/cbm/s...032/321448.gif).

 I can hear the arcing sound from area of the transformer
 when the glitch occurs, and I see no obvious external
 indications of anything sparking or shorting. I have looked
 at the voltages at the various test points noted on the
 video board schematic during normal operation, and they all
 appear OK.
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 Thanks for any help anyone can provide.

 Rob Ferguson

I would say to use an oscilloscope to monitor the circuit *driving* the flyback
transformer. I had an issue on a Compucolor II where this signal would periodically
glitch, which changed the frequency, and cause the flyback to over-voltage and spark every
time. The signal would glitch whether the flyback was plugged in or not.