4 Assembly Level Troubleshooting
122 Keysight 3458A Assembly-Level Repair Manual
Procedures in Chapter 3 of this manual to replace the (A5) Outguard Controller
assembly.
3 If after replacement of the (A5) Outguard Controller assembly the instrument is
still inoperative, the logic circuitry on the Outguard Power Supply (A6)
assembly may be causing the failure. Go to the Assemblies Removal/
Installation Procedures in Chapter 3 of this manual to replace the Outguard
Power Supply (A6) assembly.
Isolator failure
For isolation logic failures, the message “ISOLATOR FAILURE' will be displayed
after the power-on self-test is completed. The instrument then locks up and no
front panel/remote control is possible. Either the inguard or outguard isolation
logic can cause the failure. Do the following:
1 Use the Covers Removal/Installation procedures in Chapter 3 of this manual to
remove the instrument's bottom cover and bottom shield.
2 Turn the instrument on. Go to the Power Supplies troubleshooting procedures
in this chapter of the manual to check both the inguard and outguard power
supplies.
3 If the power supplies check good, the failure can either be on the Outguard
Power Supply (A6)assembly or the A/D Converter and Inguard Logic (A3)
assembly. These assemblies can cause the failure since the isolation logic
circuitry is on both assemblies and the self-test is unable to differentiate
between the failures on the two assemblies. In addition to these, the (A5)
Outguard Controller assembly could also cause the failure. However, most
failures will most be caused by the A3 or A6 assemblies.
4 Try replacing the Outguard Power Supply (A6) assembly first. Go to the
Assemblies Removal/Installation Procedures in Chapter 3 of this manual to
replace the assembly.
5 If after replacing the Outguard Power Supply (A6) assembly the test still fails,
try replacing the A/D Converter and Inguard Logic (A3) assembly. Go to the
Assemblies Removal/Installation Procedures in Chapter 3 of this manual to
replace the assembly.
6 If after replacing the Outguard Power Supply (A6) assembly the test still fails,
try replacing the (A5) Outguard Controller assembly. Go to the Assemblies
Removal/Installation Procedures in Chapter 3 of this manual to replace the
assembly.
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