IBM 3277 Troubleshooting Manual page 70

Display station models 1 and 2
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The yoke and shield assemblies are removd<l with the CRT.
To remove the CRT from the display station, proceed as
follows:
Model 1
1. Disconnect power cord at display station (under front
cover).
2. Remove left, right, and top covers (5.3.1.1).
3. Remove mask/bezel assembly by loosening the two
captive knurled head screws that hold assembly to
frame.
4. Carefully disconnect CRT anode lead. Static charge
may be present.
5. Using an insulated jumper wire, momentarily ground
CRT anode terminal to discharge static charge.
6. Disconnect yoke cable from analog card, and discon-
nect ground wire(s) from yoke shield.
7. Remove cone shield from base area of CRT:
a.
Loosen cone shield retaining shoulder screw.
b.
Rotate cone counterclockwise until locking tabs
disengage.
c.
Pull cone straight back and clear of CRT neck.
8. Remove socket from base of CRT.
9. Open new CRT carton and place pad on firm surface
close to display station so that a safe place is available
when old CRT is removed.
CAUTION
The following steps free the CR
r
trom its mounting.
The tube weighs about 4 pounds. Protect and support
CRT from excessive pressures that could cause damage
to the CRT or other components.
10. Remove top two CRT holding nuts, and remove
grounding spring.
11. Loosen the bottom two holding nuts.
12. Connect lifting strap (PN 2565197) to top CRT
mounting ears.
(It
may be necessary to slide CRT off
the threaded studs and tilt it forward to attach strap to
mounting ears.)
13. Remove bottom two holding nuts.
14. Carefully slide CRT and yoke assembly toward front of
display station and clear of unit.
15. Place CRT face down on pad.
16. Note approximate orientation of yoke with reference
to CRT.
17. Loosen yoke and shield retaining clamp and carefully
slide assembly off CRT neck.
18. Install yoke and shield assembly on new CRT in
location noted in step 16.
19. Install new CRT in reverse order, ensuring that CRT
grou nding spring (step 10) and yoke
sh
ield grou
nd
wire(s) (step 8) are reconnected.
20. Perform all Model 1 display image adjustments (5.2.1
through 5.2.1.6).
5-12
Model
2
1. Disconnect power cord at display station (under front
cover).
2. Remove left, right, and top covers (5.3.1.2).
3. Remove Contrast and Brightness control knobs.
4. Mark position of power control actuator assembly on
left side rail.
5. Remove the two power control actuator mounting
screws. (One screw attaches assembly to side rail; the
other attaches to front frame.)
6. Remove power control actuator assembly to expose
lower left CRT holding nut.
7. On units with security keylock optional feature:
a.
Mark location of keylock assembly mounting
bracket on front frame.
b.
Remove screws holding bracket to frame.
c.
Place keylock assembly aside to expose lower right
CRT holding nut.
8. Carefully disconnect CRT anode lead. Static charge
may
be
present.
9. Using an insulated jumper wire, momentarily ground
CRT anode terminal to discharge static charge.
10. Disconnect yoke cable from analog card, and discon-
nect ground wire(s) from yoke shield.
11. Remove socket from base of CRT.
12. Remove cone shield from base area of CRT:
a.
Loosen cone shield retaining shoulder screw.
b.
Rotate cone counterclockwise until locking tabs
disengage.
c.
Pull cone straight back and clear of CRT neck.
13. Open new CRT carton and place pad on firm surface
close to display station so that a safe place is available
when old CRT is removed.
CAUTION
The following steps free the CRT from its mounting.
The tube weighs about 16 pounds. Protect and support
CRT from excessive pressures that could cause damage·
to the CRT or other components.
14. Remove top two CRT holding nuts, and remove
grounding spring.
15. Loosen bottom two holding nuts.
16. Connect lifting strap (PN 2565197) to top CRT
mounting ears.
17. Remove bottom two holding nuts.
18. Carefully slide CRT and yoke assembly toward rear of
display station and clear of unit.
19. Place CRT face down on pad.
20. Note approximate orientation of yoke with reference
to CRT.

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