ADM 3a with no horizontal scan

Seth Morabito lists at
Thu Apr 7 21:50:58 CDT 2016

Hey folks,

I've been on a tear trying to resurrect old projects here, and next on
the list is an ADM 3a.

This particular 3a has no horizontal scan. None at all. I just get a
vertical line down the center of the screen. First thing I checked was
the horizontal deflector on the yoke, which seems secure.

Before I go diving into the schematics, I figured I'd ask here: Is
this a common failure mode? Has anyone else experienced no horizontal
scan on a 3a? Any tips on where to look first?

Seth Morabito
seth at

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