Thanks for the tip. I'll give him a call.
I'm certain it's the PCB set.
It was left on overnight by my son and his friend, for a total "on" time of about 18 hours.
It looked fine, and played fine, the morning after and then I turned it off.
Turned it on later in the day and it started collapsing in a cyclic pattern during a game.
It will sit on the test screens indefinately as long as they aren't the screens with the cross hatch pattern (which collapses) or the following self-test screens with the boxes that start off large and shrink down. The ones of those that do show up, just collapse to a quarter of the screen size.
There are no "hardware" or "mathbox" errors in test.
It used to do all the self-tests just fine.
During gameplay it might stop workng completely... I just played it through a few times on easy... the second time through the towers were all missing... there are 'artifacts' on the screen all the time.. the shots from the enemies in every stage are basically invisible... maybe a couple of red lines (instead of white).