80 34980A Service Guide
4 Troubleshooting and Diagnostics
Troubleshooting and Diagnostics
This chapter provides basic instructions to isolate a problem.
Troubleshooting Hints
This section provides a brief checklist of common failures. Before troubleshooting the
instrument, be sure the failure is in the instrument rather than any external connections.
Unit seems inoperative
1 Verify the ac power cord is connected to the instrument.
2 Press the front panel power switch.
3 Listen for the fan (on the right side of the instrument) to isolate a problem with the
front panel.
4 Remove all plug-in modules to verify a module is not causing the failure.
5 Verify the power supply as described on page 81.
Isolating to an assembly
1 Remove all plug-in modules from the mainframe.
2 Remove any connections to the Analog Bus.
3 Turn on power and listen for the beep and fan operation. The fan operates from the
main power supply.
4 Isolate the internal DMM by removing it from the instrument. The instrument should
turn on and pass self-test without the internal DMM installed. Disassembly
procedures begin on page 117.
Unit fails self-test
1 Check the display for the power on self test results.
2 Remove all plug-in modules from the mainframe and any connections to the Analog
Bus. Run the self-test again. A passing self-test indicates a problem with a plug-in
module. Replace the plug-in modules one at a time to isolate the failing module.
3 If the self test still fails, remove the internal DMM from the instrument. The
instrument should turn on and pass self-test without the internal DMM installed.
Disassembly procedures begin on page 117.
4 Self-test errors are described beginning on page 84.
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