HP 54520 Series Service Manual page 111

CAUTION
CAUTION
Chapter 6: Replacing Assemblies
To remove and replace the CRT monitor assembly
To remove and replace the CRT monitor assembly
The sweep board, CRT, and CRT yoke are all parts of one HP part number. They have been
adjusted as a unit and should be replaced as a unit, rather than individually. Do not remove
the yoke from the CRT. When necessary, refer to other removal procedures.
Remove the following assemblies:
e Rear panel
e@ Power supply
@ Main assembly
Discharge the post accelerator lead to the CRT mounting band only. Components will be
damaged if the post accelerator is discharged to other areas.
Discharge the CRT.
a Connect a jumper lead between the CRT mounting band CRT and a screwdriver shaft.
b Discharge the CRT.
Place the grounded screwdriver under the rubber cap of the post-accelerator lead and
momentarily touch the screwdriver to the metal clip of the lead.
Always discharge the CRT before handling. The CRT may charge up by itself even while dis-
connected. To keep it from charging, use a jumper to short the CRT post-accelerator terminal
to the CRT mounting band. Failure to discharge the CRT can result in electrical shock.
Disconnect the post-accelerator lead from the CRT by firmly squeezing the rubber
cap until the metal clip disengages from the CRT.
Detach the following cables at the sweep board or CRT.
e Intensity cable
e Monitor sweep drive ribbon cable
e CRT yoke cable and base cable
Slide the sweep board up and out of the cabinet slot.
When installing the sweep board, it may be necessary to press on the center of the outer
shield of the sweep board to allow the board to clear the cabinet support rib.
Carefully place the instrument in the front-panel-down position.
Remove the three nuts that secure the CRT to the front panel.
Remove the washer on the stud at the center of the instrument.
Remove the sweep board ground bracket.
Remove the pan-head screw that secures the CRT to the front panel.
Remove the CRT.
Reinstall the CRT with the post-accelerator terminal toward the middle of the instrument.
To install the CRT monitor assembly, reverse this procedure.
After replacing the CRT monitor assembly, and only if necessary, perform the CRT monitor
assembly adjustment procedures in chapter 4, "Calibrating and Adjusting."
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