[Coco] Screen roll on model 1

[rietveld rietveld]

Hi. Not coco but trs80 anyway

I am getting a constant vertical screen roll on my model1's original monitor. Thinking it was a problem with the monitor I just built one of Mav's composite cables. I am still getting the same vertical roll on an old Tandy vm2 as well as a newer flatscreen monitor using the comp in

It seems that the model 1 is the problem.    What should I be looking at?

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