Defeated by a Commodore 1950 Monitor

Sean Caron scaron at
Tue Dec 2 13:58:12 CST 2014

On Tue, Dec 2, 2014 at 2:33 PM, Mark J. Blair <nf6x at> wrote:
> Yes, and it's a big part of the reason that I haven't been motivated to
> get much experience fixing monitors so far! I had previous bad experience
> trying to fix a 19" Hitachi monitor for my Sun 3/60 20ish years ago
> (thought I had it narrowed down to a $70 transistor; replacement blew, too;
> ended up taking it to a shop and paying real money for somebody with a clue
> to fix it).
> I did have much better experience with a DEC VR201 recently. Its circuitry
> was a lot easier to get to for maintenance, and it had a simple failure
> mode: Blew its fuse immediately. So I powered it through a current-limited
> supply and started looking for hot spots with my IR thermometer. Hottest
> spot was a diode feeding power to a subcircuit, and second-hottest spot was
> a capacitor from that power rail to ground. Replaced the cap, monitor
> became happy.
When I was in high school and was just coming up in the field, I had the
opportunity to work at a local computer repair shop in the area that
maintained the ability to do board-level repair (ca. late 90s). There was a
guy there who was just brilliant at repairing monitors... I imagine he had
been doing it for a while so he probably had a good idea of all the tricks
of the trade and things to look out for but I was always impressed... I
felt like there was maybe a bit of art to the whole process. I don't recall
there ever being a monitor he couldn't fix given parts availability and the
budget for T&M.

Certainly watching him do it emboldened me, LOL. I remember taking on a
totally generic 15" VGA display from a trash heap some time ago and I got
lucky... easy fix... cold solder joint or a burnt out resistor or something
that you could just pick up visually. Sometimes it turns out to be easy
stuff! Too bad not in this case!

I have a Sony GDM17 that's been sitting torn apart on my bench forever that
needs a new cable spliced onto it, and one of my NeXT Megapixel Color
Displays has pooped out on me so that will have to go under the knife
someday. Not to mention my VT100! Yikes. I definitely enjoy the discussion
of diagnosis & repair of the analog side of things. Many things to learn!



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