2. Service
Pre-Troubleshooting Information
29
1 VISUAL INSPECTION. Visually inspect the interior of the
instrument for any signs of abnormal internally generated heat,
such as discolored printed circuit boards or components,
damaged insulation, or evidence of arcing. Determine and remedy
the cause of any such condition.
2 GROUND CONTINUITY TEST. Plug the power cord into the rear-
panel power receptacle. (DO NOT connect the instrument to ac
power at this time.) Using a suitable ohmmeter, check resistance
from the instrument's metallic connection (such as the rear panel
or BNC ground collar) to the ground pin on the power cord plug.
The reading must be less than 1. Flex the power cord while
making this measurement to determine whether intermittent
discontinuities exist.
3 Check any indicated front or rear panel ground terminals marked,
using the above procedure.
4 INSULATION RESISTANCE TEST. Tie the line and neutral pins of
the power cord plug together. Measure the resistance from the
instrument enclosure (chassis) to the line and neutral pins of the
power cord plug. The minimum acceptable resistance is 2 M.
Replace any component that results in a failure.
5 LINE FILTER/CABLE ASSEMBLY CHECK. Check the line fuse
and voltage selector card in the rear panel line filter/cable
assembly to verify that the instrument is properly set for the ac-
power source to be applied.
Product Performance Checks
After replacement of any assembly or module, perform the Operational
Verification Test in Chapter 1, “Performance Test,” of this manual.
Service Accessories
Service accessories for troubleshooting the 5071A are available from
Symmetricom. Table 2-1 lists the items in the 5071A Service Accessories Kit.
The list includes the name, the part number, and a brief description and use
of each item.
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