Tektronix 2235A Instruction Manual page 119

Maintenance
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2235A
Instruction
2. Set the CH 1 and the CH 2VOLTSlDIV switches to the
same position. Note switch positions for reinstal-
lation reference; then remove the knobs by pulling
them straight out from the front panel.
3. Place the instrument on its side and unsolder the
resistors from the CH 1 and CH 2 input connectors.
4. Remove the two screws securing the Attenuator
circuit board to the subpanel (located underneath
the CH 1 and CH 2 input connectors).
5. Disconnect the following plugs from the Attenuator
board, noting locations and orientations for reinstal-
lation reference:
a. P9200, a 4-wire connector located in the cutout
at the rear edge of the top attenuator shield.
b. P9991, a 4-wire connector located at the center
rear edge of the board.
6. Disconnect the following plugs from the Main circuit
board, noting locations and orientations for reinstal-
lation reference:
a. P9108, a 3-wire connector located between the
crt and the power switch extension shaft (near
the center of the board).
b. P9103, a 3-wire connector located between the
rear of the attenuator assembly and the crt.
7. Loosen the screw at the front edge of the top
attenuator shield.
8.
.
Remove the remaining six screws securing the top
attenuator shield, noting screw lengths and
locations for reinstallation reference.
9. Slide the top attenuator shield to the rear until it
clears the screw at the front edge. Lift the shield out
of the instrument.
10. Remove the screw in the left rear corner of the
Attenuator board that secures the board to the bot-
tom shield assembly.
11. Pull the Attenuator board straight back from the front
of the instrument until the switch shafts are clear of
the Front Panel board and the two Input Coupling
switch shafts (located between the front panel and
the subpanel). Lift the Attenuator board out of the
instrument.
To reinstall the Attenuator circuit board, perform the
reverse of the preceding steps.
Timing Circuit Board
T o remove the Timing circuit board, perform the following
steps.
1. Use a 1116-inch hexagonal wrench to loosen the
set-screw of the SECIDIV Variable knob. Remove
the Variable knob.
2. Lock the A and B SECIDIV knobs together and note
the position for reinstallation reference. Use a
1116-inch hexagonal wrench to loosen the set
screws securing the B SECIDIV knob; pull off the
knob.
3. Use a 111 6-inch Hex-key wrench to loosen two set
screws securing the A SECIDIV dial to the shaft
assembly. Remove the dial.
4. Remove the following connectors from the Timing
circuit board.
a. P9705, an eight-wire connector located at the
rear of the Timing circuit board.
b. P9700, a 10-wire connector located on the right
edge of the Timing circuit board.
c. P9201, a 4-wire connector located at the left
rear corner of the Timing board.
5. Remove one screw at the rear of the Attenuator cir-
cuit board (securing both the Attenuator and theTim-
ing circuit boards to the Bottom shield).
6. Remove the remaining three screws securing the
Timing circuit board to the Bottom shield.
7. Pull the Timing board straight back from the front of
the instrument until switch shaft is clear of the Front-
Panel circuit board. Lift the board out of the
instrument.
To reinstall the Timing circuit board, perform the reverse
of the preceding steps.
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by ARTEK MEDLQ
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