Tektronix 2236, Instruction Manual

Page: 160 / 350

Maintenance— 2236 Service
4. Gently replace the Multimeter Control circuit board,
aligning the interconnecting pins with their respective sock­
ets (removed in step 3).
5. Replace the CTM bottom shield (see “CTM Bottom
Shield” removal procedure).
6. Reinstall three screws securing the CTM insulator
box to the CTM circuit board (removed in step 1).
NOTE
Inspect the conductive paint and plastic shield on the
inside of the cover for damage. At the circular pad and
edge check for continuity of the conductive paint, if
either the plastic shield or the conductive paint is dam­
aged, replace the complete plastic cover.
Cathode-Ray Tube
W A R N I N G
Use care when handling a crt. Breakage of the crt
may cause high-velocity scattering of glass fragments
(implosion). Protective clothing and safety glasses
should be worn. Avoid striking the crt on any object
which may cause it to crack or implode. When storing
a crt, either place it in a protective carton or set it face
down on a smooth surface in a protected location with
a soft mat under the faceplate.
To remove the crt, perform the following steps:
1. Lift up and secure the CTM circuit board (see “CTM
Circuit Board” removal procedure).
2. Disconnect four deflection-plate wires at the middle of
the crt neck and unplug the Trace Rotation connector
(P9006) from the Front-Panel circuit board (note the connec­
tion locations and wire colors for reinstallation reference).
W A R N I N G
J
The crt anode lead and the High-Voltage Multiplier
output lead retain a high-voltage charge after the in­
strument is turned off. To avoid electrical shock, dis­
connect the High-Voltage Multiplier lead from the crt
anode lead and ground both leads to the main instru­
ment chassis.
3. Unplug the crt anode lead connector from the High-
Voltage Multiplier lead located on left side of Power-Supply
shield and discharge it to the chassis.
4. Remove two front-panel screws that retain the plastic
crt frame and light filter to the front panel. Remove the crt
frame and light filter from the instrument.
5. Remove the crt socket cap from the rear of the crt
socket for reinstallation.
6. With the rear of the instrument facing you, place the
fingers of both hands over the front edge of the front
subpanel. Then, using both thumbs, press forward gently on
the crt funnel near the front of the crt. When the crt base
pins disengage from the socket, remove the crt and the crt
shield through the instrument front subpanel. Place the crt in
a safe place until it is ready to reinstall. If the plastic crt
comer pads fall out, save them for reinstallation.
To reinstall the crt, perform the following steps:
7. Reinstall any plastic crt corner pads that are out of
place. Insert the crt, crt shield, anode lead, and Trace Rota­
tion leads through the front-panel opening. Ensure all pins
are straight and that the indexing keys on the crt base,
socket, and shield are aligned. Make sure that the ground
clip makes contact only with the outside of the crt shield.
8. Push the crt base into the socket. Verify that the crt
base and socket are flush together as viewed from the rear
and that the crt is seated properly in the front-panel
opening.
9. Reinstall the crt socket cap to the rear of the crt
socket (removed in step 5).
10. Reinstall the crt frame and light filter; then secure
them with two front-panel screws (removed in step 4).
11. Reconnect the crt anode lead to the High-Voltage
Multiplier lead (disconnected in step 3).
12. Reconnect the four deflection-plate wires and the
Trace Rotation connector (disconnected in step 2).
13. Unlock the CTM circuit board and lower it into the
instrument (see “CTM Circuit Board” removal procedure).
6-28