Had to power up the ESD HV supplies this morning for testing the charge on the optic.  Once again one of the supplies would not stay on.  As it ran through diagnostics during start up it would trip off.  We replaced this unit.  The next problem was the DAC cable was on the wrong connection on the AI board.  This probably happened during Power board check a few weeks ago.  After this was fixed had to unplug and plug back in DAC cable at ESD to clear error there.  This has been seen in the past and resembles a blown chassis by railing outputs at 430Vdc.  The system was then restarted and appears to be working