Great, my VT52 is shot.

Jon Elson elson at
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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