Tektronix 2235A Instruction Manual page 121

Maintenance
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2235A
Instruction
T o reinstall the Front Panel circuit board, perform the
reverse of the preceding steps.
Main Circuit Board
All components on the Main circuit board are accessible
either directly or by removing the crt, the Bottom shield,
Attenuator, Timing circuit-board module, or the Power-
Supply shield. Removal of the Main circuit board is
required only when it is necessary to replace the board
with a new one.
T o remove the Main circuit board, perform the following
steps:
1. Remove the power-supply shields (see Power Sup-
ply Shields removal procedure).
2. Remove the Alt Sweep circuit board (see Alt Sweep
Circuit Board removal procedure).
3. Disconnect the following connectors from the Main
circuit board, noting locations and orientations for
reinstallation reference:
a. P9870B, a 4-wire connector (5-wire body)
located at the left edge of the board in front of
the delay line.
b. P9108, a 4-wire connector located near the
center of the board between the crt shield and
the power-switch extension shaft.
c. P9103, a 4-wire connector located between the
left rear corner of the attenuator shield and the
crt shield.
d. P9884, a 2-wire connector located at the front
edge of the board between the attenuator shield
and the crt.
e. P9644, a 3-wire connector located at the right
edge of the board to the rear of the Timing circuit
board.
f. P9882, a 2-wire connector located at the front
edge of the board, below the crt (accessible
from the bottom side of the instrument).
4. Disconnect P9991, a 4-wire connector located at
the center rear edge of the Attenuator circuit board.
5. Disconnect the following connectors from the
Timing circuit board:
a. P9705, an 8-wire connector located at the rear
of the board.
b. P9700, a 10-wire connector located at the right
side of the board.
6. Disconnect the four deflection leads from the crt
neckpins, noting locations and orientations for
reinstallation reference.
7. Unsolder the delay-line wires from the Main circuit
board, noting wire colors and locations for reinstal-
lation reference. (One end of the delay line is
soldered to the component side of the Main board
and the other end is soldered to the opposite side.
8. Unsolder the rear-panel EXT Z AXIS connector wire
from the Main circuit board.
9. Unsolderthe five crt base pin wires (W9870) from the
Main board. The wires are located adjacent to the
High Voltage Multiplier (U975) in the Power Supply
section.
10. Unsolder the following Line Filter wires from the
Main circuit board:
a. The gray-black-yellow wire from the solder pad
labeled W9040.
b. The gray-brown-white wire from the solder pad
labeled W91090.
11. Remove the FOCUS control knob assembly by
pulling it straight out from the front panel.
12. Remove the POWER switch extension-shaft
assembly as follows:
a. Press in the POWER button to the ON position.
b. Insert a scriber (or similar tool) into the notch
between the end of the switch shaft and the end
of the extension shaft and gently pry the con-
nection apart.
c. Push the extension shaft forward, then side-
ways, to clear the switch shaft.
d. Pull the extension shaft back and out of the
instrument.
13. Remove the two screws that secure the power-
supply transistor heat sink assembly to the right side
of the chassis.
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ARTEK MEDU
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