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8751A power on error seems to be in error

Question asked by gstanley001 on Aug 23, 2015
I have an 8751A S/N 3315J01210 w opt 2 that reports a power on error and fails tests 16,17 and 18.  The latter 3 tests are Rch, Ach and Bch ADC & Post Regulator tests respectively.  The reports point to A40 and the +18 as being at issue.  However all of the regulated supplies and their semi-regulated input supplies are well in spec per an 8753 service manual.  Also none of the UC2834s are signalling fault/overload.  All supplies seem to be well in spec and free of AC ripple or noise.  As a network analyzer nothing seems to be wrong other than the apparently erroneous error reports.

I suspect that the problem may be on the CPU board A1 but do not have any service information/schematic  for the board or even a service note to decode the LEDs on the board.  Could you point me to good service information for this unit such as manual 08751-90031.  This manual does not seem to be available in the field despite it being shown in the catalogs as option 915.