HP 85020A Operating And Service Manual page 59

Model 85020A/B
Service
Replacement of the Al Bridge Microcircuit Assembly
The bridge microcircuit assembly Al, illustrated in Figure 8-6,
includes input port connector Jl and test port, connector J2 and
reference termination ATI. This assembly may be replaced on an
exchange basis at considerable cost savings. Refer to Section VI
of this manual for the part numbers for new and exchange
assemblies. Since the instrument serial number label must be
removed for access to the bridge assembly, each replacement bridge
assembly is supplied with a replacement blank serial number label.
The instrument serial number should be typed on this label, which
is then applied to the instrument following bridge assembly
replacement.
CAUTION
The 85020A/B Directional Bridge
microcircuit is 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.
Do not attempt to disassemble or repair
the bridge microcircuit assembly Al,
including connectors Jl and J2 and
reference termination ATI* Do not remove
or loosen any screws on this assembly. Any
attempt to perform any disassembly or
repair not clearly outlined in this
section will automatically void the
warranty.
To remove the bridge microcircuit assembly Al, proceed as follows:
1. Type the serial number of the 85020A/B Directional Bridge on
the rear-panel label supplied with the new or replacement
bridqe assembly.
2. Remove the two screws holding the port cover (the test port
end plate).
3. Remove the port cover.
4. Slide the top dress cover out of the grey 85020A/B Bridge
frame.
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