PDP 11 gear finally moved

tony duell ard at p850ug1.demon.co.uk
Fri Jul 17 14:23:11 CDT 2015

> When I repaired my VT100s I had to replace all the electrolytic caps on the
> monitor control board to cure the screen wobble. Before doing so I had
> reformed them all and I had tested them all for ESR and they had all tested
> fine so I was unable to determine which of them was the bad one. Perhaps
> there is other more professional test equipment I could use that would have
> helped, I don't know. I did keep all the original caps though (somewhere).

Are you saying that if you put any of the original capacitors back (leaving new 
ones in all other locations) you get screen wobble. If so, I am not sure I 
believe you. It's been some years since I repaired a VT100, but from what I
remember there are plenty of capacitors that simply could not cause
screen wobble no matter what they were doing.

Or did you recap the board and find that it then worked. In which case (a)
perhaps only one of the capacitors was faulty or (b) it was actually a dry


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