HP 8753E - Remove the Assemblies

If the green LEDs are now on, the Al5 preregulator and A8 post regulator are
working properly and the trouble is excessive loading somewhere after the
motherboard connections at A8. Continue to “Remove the Assemblies”.
Remove the Assemblies
1. Switch off the analyzer.
2. Install A8. Remove the jumper from A8TP2 (AGND) to chassis ground.
3. Remove or disconnect all the assemblies listed below. (See Figure 5-5.)
Alwags suvitch ofl the anulgzer before removing or diswnnectircg an
ass&lg.
Al0 digital IF
All phase lock
Al2 reference
Al3 fractional-N analog
Al4 fractional-N digital
A19 graphics processor
4. Switch on the analyzer and observe the green LEDs on A8.
q If any of the green LEDs are off or flashing, it is not likely that any of
the assemblies listed above is causing the problem. Continue to “Briefly
Disable the Shutdown Circuitry“.
q If alI green LEDs are now on, one or more of the above assemblies may be
faulty. Continue to next step.
5. Switch off the analyzer.
6. Reinstall each assembly one at a time. Switch on the analyzer after each
assembly is instaIled. The assembly that causes the green LEDs to go off or
flash could be faulty.
Note
It is possible, however, that this condition is caused by the
A8 post regulator not supplying enough current. ‘Ib check
this, reinstall the assemblies in a different order to change the
loading. If the same assembly appears to be faulty, replace that
assembly. If a different assembly appears faulty, A8 is most
likely faulty (unless both of the other assemblies are faulty).
Power Supply Troubleshooting 5-15