My Barco 708 video has been acting strange for a while now, and finallly it seems that the em focus has gone completely out. It was just suddenly out of focus, and the focus slowly varies. I have been biding my time looking for a good deal on tubes, so my current tubes are really high hour. I just thought that it was a result of the tubes.

I just occurred to me that it would be bad if I bought tubes and upon installing them the projector still didn't work. So, should I suspect another issue, or is this a typical situation with high hour tubes? Attached is a MS Paint rendering of the problems I had previously had, which got worse the higher resolution I sent to the projector.

Well the set does not have EM focusing, so that could be part of the problem..:D

If all tubes change equally in focus, you're looking at fluctuating HV, a bad quadrupler, bad focus block (just had one of those the other day on a 708), a bad CRT socket... but not bad tubes.