Briefly Disable The Shutdown Circuitry - Agilent Technologies 8719ET Service Manual

8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers

Briefly Disable the Shutdown Circuitry

In this step, you shutdown and disable the protective circuitry for a short time, forcing on
the supplies (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. Connect A8TP4 (SDIS) to chassis ground with a jumper wire.
2. Switch on the analyzer and note the test points of any LEDs that are off. Immediately
remove the jumper wire.
3. 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.
Digital IF (A10)
Phase lock (A11)
Reference (A12)
Fractional-N analog (A13)
Fractional-N digital (A14)
Display (A18)
Display Interface (A22)
4. Switch off the analyzer.
NOTE Always switch off the analyzer before removing or disconnecting assemblies.
To identify specific cables and assemblies that are not shown in this chapter,
refer to
When extensive disassembly is required, refer to
Replacement and Post-Repair Procedures."
Service Guide
Chapter 13 , "Replaceable Parts."
If the Green LEDs of the Post Regulator (A8) Are Not All ON
Chapter 14 , "Assembly
Power Supply Troubleshooting
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