Great, my VT52 is shot.
elson at pico-systems.com
Sun Apr 19 10:22:31 CDT 2020
After looking at the video, and Mattis' description of the
sweep method, I'm guessing a counter
in the chain has gone bad. Assuming this uses a 5 x 7
character matrix, then there would be probably
a divide by 6 for the scan across each character plus space
between, then a counter for the number
of characters per line, a counter for the 8 or 9 raster scan
lines for each row, and then a counter
for the number of rows. At least one of those counters
might be counting too fast. Does the vertical just give one
reset pulse, or does it give a pulse to bump the trace down
the screen one scan line at a
time? Also, a cap in the vertical sweep circuit may have
gone bad, causing the vertical to move too
fast, as evidenced by sloping lines on the screen.
Just guessing from a distance.
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