HP 3457A Service Manual page 141

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3457A Replaceable Parts
6-21. Top Cover Removal
6-22. No prior disassembly of the instrument is required to remove the Top Cover. Remove the Top Cover
as follows:
a. Remove the power cord and all external input connections from the HP 3457A.
b. Turn the unit upside down and loosen the six screws in the bottom cover. (These are captive screws.
It is not necessary to remove them completely).
c. Return the unit to an upright position and remove the top cover.
d. To replace the top cover, reverse the order of steps a through c.
6-23. Display Assembly Removal
6-24. The Top Cover must be removed prior to removing the Display Assembly, Remove the Display
Assembly as follows:
a, Remove the Top Cover as described in paragraph 6-21.
b. Disconnect the plug on the back of the Display Assembly.
The pins of the plug connected to the display assembly are quite fragile.
Disconnect the plug by pulling on the ribbon cable rather than the plug itself. *
c. Remove the two screws attaching the Display Assembly to the Front Panel.
d, Remove the Display Assembly from the Front Panel.
e. To replace the Display Assembly, reverse the order of steps a through d.
6-25. Digital (A1 or A11) Assembly Removal
6-26. It will be necessary to remove the Top Cover prior to removing the Digital Assembly. To remove the
Digital Assembly:
a. Remove the Top Cover as described in paragraph 6-21.
b. Remove the four screws holding the shield to the Digital Assembly and remove the shield.
c. Remove the power switch pushrod. Grasp the pushrod firmly near the power switch and pull it off
the power switch shaft.
d. Disconnect connectors P501 (Use the white pull strap), P502, P701 and P702 from the Digital
Assembly.
e. Remove the two screws attaching the HPIB Connector/Heat Sink bracket to the rear panel.