Troubleshooting Procedures - HP 85020A Operating And Service Manual

Model 8 5020A/B
Service
TROUBLESHOOTING PROCEDURES
If a problem persists following the Operator's Check in Section
III and the Performance Tests in Section IV, perform the
troubleshooting procedures outlined below to isolate the cause and
correct the problem. Refer to the troubleshooting flow diagram in
Figure 8-4. Instructions for repair or replacement of defective
components are provided following the troubleshootina procedures.
CAUTION
The 85020A/B Directional Bridges contain
microcircuits that are highly sensitive to
electrostatic discharge (ESD). For service
purposes, a work station equipped with an
anti-static surface must be used and a
grounded wrist strap must be worn. Never
touch the center contacts of the
connectors with the fingers. Ground the
leads of the digital multimeter by
touching them to the grounded instrument
chassis before making measurements.
Internal Access
To obtain access to the interior of the 85020A/B for
troubleshooting and repair purposes, proceed as follows:
1. Remove the two screws holding the port cover (the test port
end plate).
2. Remove the port cover.
3. Slide the top dress cover out of the grey bridge housing. The
interior of the 85020A/B is now accessible.
Cable Continuity Check
1. Use a digital multimeter (DMM) to check the continuity of
power cable W1 from the connector pins to the wire connections
inside the bridge housing. Table 8-1 lists the W1 connector
pins and the corresponding wires.
2. If there are discontinuities in any of the wires replace cable
Wl, following the instructions outlined under Repair and
Replacement Procedures. Repeat the performance tests in
Section IV.
8-7