Switch Maintenance; Repair And Replacement - HP 1331A Operating And Service Manual

Service
cleaner or with a mild soap and water solution .
Excess grease can be removed with a degreaser s uch
as M-180 FREON T F DEGREASER produced by
Miller-Stevenson Company.
8-22. Corroded spots a re best removed with soap
and water. Stubborn residues can be removed with a
fine a brasive. When using abrasives, be careful that
fine particules do not fall into the instrument. Such
areas s hould be protected from further corrosion by
a n a pplication of a s ilicone resin such as GE DRI-
FILM 88.
8-23. SWITCH MAINTENANCE.
8-24. The push button switches used in this instru-
ment have been designed for long, trouble-free
service. In the event tha t one of these switches
becomes defective, replacement ra ther than repa ir is
recommended.
8-25. REPAIR AND REPLACEMENT.
8-26. The following paragraphs provide procedures
for replacement of assemblies, s ubassemblies, a nd
components. Special servicing instructions for the
etched circuit boards a re provided in paragra ph
8-32. Section VI provides a detai led parts lists for
use in ordering replacement parts.
8-27. CRT REMOVAL AND INSTALLATION.
WARN ING '
To prevent persona l injury, wear a face
mas k or goggles when h a ndling the CRT.
Wear protective gloves and handle the
CRT carefully.
8-28. To remove the CRT, proceed as follows:
a . Remove top, bottom, a nd both side covers.
b. Remove two screws in left frame MP4 holding
high voltage power s upply board A3.
c. Disengage high voltage power supply board
from its socket (not necessary to remove board entire-
ly).
d. Reach under high voltage power supply
board a nd remove wires from CRT neck pins.
e. Remove contrast screen MP3! by pulling up-
wards.
f.
Remove CRT b ezel MP23 by removing four
screws.
g. Remove CRT socket cover MP17 by removing
four screws.
8-2
Model 1331A
h . Loosen CRT base cla mp screw on CRT
s hield s upport MP19.
i. Remove two screws in right frame MP5
holding low voltage rectifier board A2.
j. Slide low voltage rectifier board toward top
of ins trument (not n ecessary to remove board entire-
ly).
k. Remove collimator lead from CRT by
gras ping center of dot fastener with long nose
pliers and pulling directly a way from CRT.
I. Remove two screws holding flex lead con-
nector A 7Pl.
m. Remove fiber board a nd 3 rubber gaskets
from flex lead connector A 7Pl.
WARNING
I
Both the CRT post accelerator and the
high voltage tripler can retain a poten-
tia lly dangerous charge. Discharge both
to chassis before ha ndling.
n . Remove flex lead from flex lead connector.
~
Attempting to remove the CRT socket at
an angle can break the CRT base and
keyway.
o. Gently pry CRT socket from CRT base.
p. Grasp CRT flex lea d with one hand and place
fingers of other h and against base of CRT.
q. Apply steady forward pressure to base of CRT
while guiding flex lead through large circular hole in
CRT s hield.
r . When face of CRT is clear of front panel,
grasp CRT at edges of face and pull forward until
CRT is clear of front panel.
8-29.
To install CRT, reverse removal procedure.
Observe the following precautions:
a. Before tightening CRT hase cla mp screw
on CRT s hield support MP19, en sure that CRT
graticule is square with front pa nel.
b. Before installing wires on CRT neck pins,
ens ure that neck pins are accuately centered in
s lot in CRT shield. To center, loosen two nuts holding
C RT s hield support MP19 to CRT shield and move
shield forward or backward until pins are centered.
Tighten nuts.