Agilent Technologies 8753ES Option 011 Service Manual page 205

Briefly Disable the Shutdown Circuitry
In this step, you shutdown the protective circuitry for a short time, and the supplies are
forced on (including shorted supplies) with a 100% duty cycle.
CAUTION Damage to components or to circuit traces may occur if A8TP4 (SDIS) is
shorted to chassis ground for more than a few seconds while supplies are
shorted.
1. Switch off the analyzer.
2. Connect A8TP4 (SDIS) to chassis ground with a jumper wire.
3. Switch on the analyzer and note the signal mnemonics and test points of any LEDs that
are off. Immediately remove the jumper wire.
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.
them from most to least accessible.
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
Replacement and Post-Repair Procedures."
• Refer to
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
Chapter 5
Table 5-4 shows the best order in which to remove them, sorting
Table 5-4
Chapter 13 , "Replaceable Parts,"
Power Supply Troubleshooting
If the Green LEDs of the A8 Are Not All ON
also lists any associated assemblies that
Chapter 14 , "Assembly
to identify specific cables and
5-15