Agilent Technologies 4395A, Service Manual

Page: 211 / 343

FIND OUT WHY THE A50 SHUTDO WN LED IS OFF
Use this pro cedure when the fan is rotating. If the fan is not rotating, see the FIND OUT
WHY THE F AN IS NOT R OT A TING .
If the fan is rotating and the A50 SHUTDO WN LED is o, the problem may b e in the A50
DC-DC Con v erter and an y of assem blies obtaining the p o w er from +5 VD supply and the
higher p o w er supplies.
1. Disconnect the Cable from the A1J10
T urn the analyzer p o w er o. Disconnect the cable from A1J10. T urn the analyzer p o w er on.
If the A50 SHUTDO WN LED go es on, replace the A1 CPU.
If the A50 SHUTDO WN LED is still o, the A1 CPU is v eried. T urn the analyzer p o w er
o and reconnect the cable to the A1J10. Con tinue with the next R emove Assemblies .
2. Remo v e Assemblies
a. T urn the analyzer p o w er o.
b. Remo v e the assem blies, A2, A3, A5, A7, A8 and A51.
c. T urn the analyzer p o w er on.
If the A50 SHUTDO WN LED is still o, insp ect the A20 motherb oard for soldering
bridges and shorted traces on the F AN PO WER and the F AN LOCK signal paths.
If the A50 SHUTDO WN LED go es on, the A20 motherb oard are v eried. Con tinue with
the next step.
d. Reinstall eac h assem bly one at a time. T urn the analyzer p o w er on after eac h is installed.
The assem bly that causes the A50 SHUTDO WN LED to go o is the most probable faulty
assem bly . Replace the assem bly . If no assem bly makes the A50 SHUTDO WN LED o,
con tinue with the next Disc onne ct the Cable fr om the A9J2 .
3. Disconnect the Cable from the A9J2
T urn the analyzer p o w er o and reinstall all of assem blies. Disconnect the cable from the
A9J2 and turn the analyzer p o w er on. The lo cation of the A9J2 is sho wn in the Figure 7-5 .
If the A50 SHUTDO WN LED go es o, the A9 is faulty . Replace the A9 assem bly .
P o w er Supply Troubleshooting 7-7