80 Chapter 4 Assembly Level Troubleshooting
Refer to the Assemblies Removal/Installation Procedures in Chapter 3 of this
manual to replace a defective assembly.
Miscellaneous Failures The following failures are those that are not detected by either the self-tests
or the performance tests.
GPIB Failure (Self-Test passes)
This failure is normally caused by a defective GPIB Connector. Try cleaning
the connector. If still inoperative, try replacing the Outguard Controller (A5)
assembly. Go to the Assemblies Removal/Installation Procedures in
Chapter 3 of this manual to replace the assembly.
Ext Out Failure
This failure can be caused by a defective cable or an inoperative isolation
logic circuitry. Note that the Ext Out function can be disabled by the
"EXTOUT 0" command. Be sure the function is enabled before
troubleshooting the failure. To enable the function, reset the instrument.
To troubleshoot an Ext Out failure, do the following:
1. Use the Covers Removal/Installation Procedures in Chapter 3 of this
manual to remove the instrument's bottom cover.
2. Refer to Figure 29 to locate the Ext Out/Ext Trig cable plugged in on
the Outguard Power Supply (A6) assembly. Unplug the cable from
socket P301.
3. Connect an oscilloscope (a logic probe can also be used) to the Ext
Out connection on the Ext Out/Ext Trig connector (P301). The Ext
Out connection is on the connector's outside pin facing the inguard.
4. Turn the instrument on and wait until it completes its self-test. When
the instrument starts to trigger, a 1µS negative going pulse should be
detected by the oscilloscope (or logic probe) at each trigger.
5. If a pulse is detected, check the cable going to the Ext Out connector
on the rear panel.
6. If no pulse is detected, the isolation logic circuitry or the A/D
Converter and Inguard Logic (A3) assembly may be defective. Try
replacing the A/D Converter and Inguard Logic (A3) assembly first,
then, if still inoperative, try replacing the Outguard Power Supply
A5 03458-66515
214 Optional RAM 1 Low Outguard Controller A5 03458-66505
A5 03458-66515
Table 9. Self-Test Error Messages and Probable Causes
Error
Number
Error Message Probable Cause Ref
Desig
Assembly
Part Number
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