Assembly Level Troubleshooting 4
Keysight 3458A Assembly-Level Repair Manual 121
3458A inoperative with blank display
A blank display can indicate two things: either the instrument is completely
inoperative or the display is defective. Do the following:
1 Turn the instrument on. The instrument should beep once and then go through
its power-on self-test. During this time, you should hear some relays
switching. When completed, the instrument will beep once again. This
indicates that the instrument has completed its power-on self-test.
2 If the above power-on self-test sequence takes place (i.e., a beep is output and
the relays switch), the Display Logic (A7) assembly is most likely defective. Go
to the Assemblies Removal/Installation Procedures in Chapter 3 of this manual
to replace the Display Logic (A7) assembly.
3 If the power-on self-test sequence does not take place, first check for a
defective outguard power supply. Go to the Power Supplies troubleshooting
procedures in this chapter of the manual to check the supplies.
4 If the outguard power supplies are defective, go to the Assemblies Removal/
Installation Procedures in Chapter 3 of this manual to replace the Outguard
Power Supply (A6) assembly.
5 If the outguard power supplies check good, the Outguard Controller (A5)
assembly may be defective. Go to the Assemblies Removal/Installation
Procedures in Chapter 3 of this manual to replace the Outguard Controller (A5)
assembly.
6 If after replacement of the Outguard Controller (A5) 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.
3458A inoperative with unintelligible messages in display
This normally indicates that the Display Logic is probably working but that the
Outguard Logic may be inoperative. Do the following:
1 First check for a defective outguard power supply. Go to the Power Supplies
troubleshooting procedures in this section of the manual to check the supplies.
2 If the outguard power supplies check good, the Outguard Controller (A5)
assembly may be defective. Go to the Assemblies Removal/Installation
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