Fluke 8842a instruction manual Troubleshooting

Maintenance 6

TROUBLESHOOTING

If the display lights up, perform the self-test by pressing the SRQ button for 3 seconds. (Remember, the input terminals must be disconnected from the test leads during the self- tests. Otherwise, the 8842A may indicate errors are present.) The test numbers will appear consecutively. "ERROR" will appear on the display if a test should fail. The 8842A can be held in each of the test configurations by momentarily pressing the SRQ button. (Press any button to continue the tests.) With the description of the self-tests given below, it may be possible to isolate the failure. For reference, the states of various switches and logic lines are shown in Table 6-16 for each function, range, and reading rate.

If only one or a few failures appear in the self-tests, the problem is usually in the DC Scaling circuit. By carefully analyzing which failure(s) occurred, the fault can be located to within a few components. (Table 6-17 shows which components are exercised by each of the analog tests.) The heading DC Scaling Troubleshooting provides detailed instructions on locating and repairing DC Scaling circuit problems. However, before troubleshooting the DC Scaling circuit, all of the power supply levels should be measured to verify they are within the limits specified in Table 6-23 under Power Supply Troubleshooting, later in this section.

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