This morning when I came in I found the HAM2/3 ISIs tripped.  I have tracked this down to what I believe to be a DAC communication problem in the front end.

While the models show output on their DACs, the IOP shows no corresponding DAC output on the same channels.  There are no error flag whatesoever to indicate that there might be a problem.  None of the watchdogs on this machine are currently tripped.

The image below show the DAC_MONITOR screens for H1IOPSEIH23, which shows zero on all outputs, and H1ISIHAM3, which shows and output of -958 counts on CH 8.