🚀 go-pugleaf

I have a Mac 512 upgraded to a Plus at home that had a similar problem.
First the screen had the "shimmies" a.k.a. waviness that came and went at
random intervals.  Later the screen degraded to a single bright vertical
line running the full height of the screen and blackness elsewhere.
Fortunately, there were several messages on the net which described the
problem and offered potential fixes.

It turned out that a solder joint on the Molex-type plastic contector that
connects the analog (vertical) board to the CRT yoke had failed.  Reheating
the joint solved the problem completely (not even any shimmies!) but I had
a relapse about a month later.  The same joint was at fault and so a quick
fix got me back on my feet.  Recently the screen sometimes momentarily
displays a bright horizontal line that is often associated with an audible
pop.  I think that the Molex connector itself is failing but I haven't
gotten around to replacing it yet.

Hope this helps.

Caveat: I'm mostly a software person ... definitely not an EE!

Dave Sappington
Inst. for Parallel Computation
U. of Virginia
des7f@virginia.edu