Eht Bleed Assembly - IBM 3279 2A Maintenance Information

CRT Neck with Convergence
Assembly
CRT Neck
Deflection Coils Deflection Coils
Coil Centers
within 2mm
of center line
Figure 4-8. Convergence/Purity Coil Assembly
4.8.4 EHT Bleed Assembly
4.8.4.1 Removal
1. Switch power off and remove the mainline
power cable from the power socket.
2. Remove the power supply card (section 4.5.2),
analog card (section 4.5.4), and amplifier card
(section 4.8.1)
DANGER
Do not let onytlling fall on tile tube neck.
3. Loosen the two screws holding the bleed
assembly/amplifier card bracket in the top of
the box, and remove the assembly.
DANGER
TIle CRT retaim a capacitive charge after tile
EHT lead "... bun discolllll!Cled
(step
4). It must
be discharged to g,..,.,nd witll a suitably i,.,talled
lead befon tile CRT is handled or tile EHT lead
is ncolllll!CleJ. EllfNn that
tile
discharge lead is
COIUINIed to gl'Ollnd BEFORE tONClling it onto
tile CRT colllll!ClOl'.
4. Supporting the bleed assembly, unplug the EBT
cable from the top of the CRT. Lift the rubber
cap at the edge to break the airlock, grasp the
cap finnly, rock it to one side, and lift.
3279 MIM
I
nterelectrode
gap
Angular Alignment
:=:
~
Tolerance ± 5°
5. Disconnect the ground connector at the prime
power box (see Figure 6-5).
6. Withdraw the bleed assembly/bracket, remove
two securing screws, and take the bleed
assembly from the bracket.
4.8.4.2 Replacemeot
1. Mount the bleed assembly on the bleed
assembly/amplifier card bracket and secure it
using the two screws removed in step 6 of
section 4.8.4.1.
2. Connect the bleed assembly ground cable to the
prime power box.
3. Connect the EHT cable to the CRT.
4. Attach the bracket to the display and tighten
the two screws loosened in step 3 of section
4.8.4.1.
5. Reinstall the analog card (see section 4.5.4).
CAUllON
Verify tbat all grouod .. ires are recoooected
secorely. Refer to Figure 6-5 for grouoding
details.
6. Reinstall the power supply card and the
amplifier card and make all connections.
7. Ensure that all ground connections are replaced.
Chapter 4. Removal and Replacement Procedures 4-9