Assembly Level Troubleshooting 4
Keysight 3458A Assembly-Level Repair Manual 135
7 If the power supply voltages are now good, the Outguard Controller (A5)
assembly is defective. Go to the Assemblies Removal/Installation Procedures
in Chapter 3 of this manual to replace the assembly.
8 If the voltage is still low, the Outguard Power Supply (A6) assembly is
defective. Go to the Assemblies Removal/Installation Procedures in Chapter 3
of this manual to replace the assembly.
Inguard power supplies troubleshooting
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, if not previously
removed.
2 Refer to Figure 4-3. With the test digital multimeter, check for
+5 V (±0.13 V), +18 V (±1.8 V), and - 18 V (±1.8 V) at the test points shown in
the figure.
3 If all voltages are good, the power supply assembly is good.
4 If a voltage is high, the Inguard Power Supply (A4) assembly is defective. Go to
the Assemblies Removal/Installation Procedures in Chapter 3 of this manual to
replace the assembly.
5 If a voltage is low, other assemblies in the inguard may be loading down the
power supply. Continue with the next step.
6 Refer to Figure 4-3 to locate the gray 20-pin cable that connects the Inguard
Power Supply (A4) assembly to the DC Circuitry (A1) assembly. Unplug the
cable at the power supply assembly.
7 If the power supply voltage that was low is now good, the DC Circuitry (A1)
assembly is defective. Go to the Assemblies Removal/Installation Procedures
in Chapter 3 of this manual to replace the assembly.
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