Agilent Technologies PSA Series Service Manual page 157

To further isolate the failure in the remaining "minimum assemblies",
NOTE
measure the resistance (with the power turned off) from the power
supply test points on the digital IF extender board to ACOM on the
extender board. Make the measurements with the digital IF board
removed from the extender board.
Check for shorts (zero Ω) or very low resistance (approx. 1 Ω). If a short
or low resistance is measured, pull the remaining boards from the
instrument in the following order, and recheck the shorted test point
after each board is pulled. Note that the resistance will be different
from the table, but you should be able to tell if the shorted condition has
changed. First pull the A26 CPU assembly, and finally the A5 Power
Supply.
Chapter 7
Troubleshooting the Processor, Power Supply, and Display
Supply Approximate Resistance
+5.2 VDC
−5.2 VDC
+15 VDC
−15 VDC
+9 VDC
+32 VDC
Isolating an A5 Power Supply Problem
(Ω)
41
47
366
141
78
939
157