Chapter 5 5-15
Power Supply Troubleshooting
If the Green LEDs of the A8 Are Not All ON
4. Refer to the block diagram at the end of this chapter and do the following:
• Note the mnemonics of any additional signals that may connect to any A8 test point
that showed a fault in the previous step.
• Cross-reference all assemblies that use the power supplies whose A8 LEDs went out
when A8TP4 (SDIS) was connected to chassis ground.
• Make a list of these assemblies.
• Delete the following assemblies from your list as they have already been verified
earlier in this section.
A10 digital IF
A11 phase lock
A12 reference
A13 fractional-N analog
A14 fractional-N digital
A19 graphics processor
5. Switch off the analyzer.
6. Of those assemblies that are left on the list, remove or disconnect them from the
analyzer one at a time. Table 5-4 shows the best order in which to remove them, sorting
them from most to least accessible. Table 5-4 also lists any associated assemblies that
are supplied by the assembly that is being removed. After each assembly is removed or
disconnected, switch on the analyzer and observe the LEDs.
CAUTION
• Always switch off the analyzer before removing or disconnecting
assemblies.
• When extensive disassembly is required, refer to Chapter 14 , “Assembly
Replacement and Post-Repair Procedures.”
• Refer to Chapter 13 , “Replaceable Parts,” to identify specific cables and
assemblies that are not shown in this chapter.
• If all the LEDs light, the assembly (or one receiving power from it) that allows them to
light is faulty.
• If the LEDs are still not on steadily, continue to “Inspect the Motherboard” on
page 5-16.
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