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Positional Hum/Color Drift

On Thursday, May 30, 1996, I upload a message concerning our positional hum

Thanks for the many good suggestions and the quickness of response.

The problem is not fully resolved as we are currently in process of repairing
the original electrical installation of our video equipment, as the ground of
the system has too much current in it.

Yes, the problem seems to be a ground loop (or loops), in the electrical supply
system to our Rank and other areas.  Work is in progress.  Thanks again to all.

At the same time I have been looking for the cause of color drift.
(Rank MKIIIC enhanced/Renasance 888/DUI/DigitalVision system.)  Seems the LP X
FP and LP2 X FP2 waveforms from the shading waveform generator board are AC
coupled and the DC change during a pan and/or zoom cause a color drift via the
Festival board.  Also a slow color drift is seemingly caused by the burn cell
output not being perfectly constant.  The waveform generator problem I have
resolved by DC coupling the two waveforms butI do not know what to do about the
burn cell problem. (Seems that the original equipment burn cell power supply is
at fault but a couple hours looking at it makes me think it is working as well
as it can.)

Any help on this would be appreciated !  Thanks !

--- End of forwarded message from a.burnham at genie.com