TM 11-6625-2735-14-1
Vertical Mode-Gain Switch Board Removal. The Ver-
tical Mode-Gain Switch board and the Channel 1 and
Channel 2 attenuators are removed as a unit.
1. Remove the Vertical Preamp circuit-board as outlin-
ed previously.
2. Remove the two UNCAL light lenses (VAR
VOLTS/DIV UNCAL). Pry them away from front panel with
a fingernail and pull them straight out
3. Remove the VAR and VOLTS/DIV knobs. Set these
knobs fully clockwise and loosen their setscrews. This
requires a 1/16-inch Allen wrench.
4. Remove the AC-G ND-DC switch knobs by pulling
the knobs away from the switch, using a tight finger-grip.
5. Remove both attenuator shields, using a small
Phillips screwdriver (each is held with five screws and
washers),
6. Disconnect four ribbon-cables from the Vertical
Mode-Gain Switch board and confirm the number of wires
in each cable with its plug number in the following list.
Note the locations of cables to facilitate correct reinstalla-
tion.
a. Disconnect a five-wire cable from the Main Interface
board at P300.
b. Disconnect a one-wire cable from the Main inter-
face board at P128.
c. Disconnect two three-wire cables from the
VOLTS/DIV sensitivity indicator-lights at P310 and P320.
7. Unsolder the braid connecting the CH 2 attenuator
to the Main Interface, at the Main Interface board.
8. Remove the four nuts that secure the attenuators to
the front casting and remove the two screws that mount
the board to two posts on the main chassis.
9. Remove the Vertical Mode-Gain Switch circuit-
board and attenuator assembly from the instrument, using
care to prevent damage to any of the components as the
board is removed.
To install the Vertical Mode-Gain Switch circuit-board
and attenuator assembly, reverse the removal procedure.
To align the VERT MODE switch pushbuttons, hold the
assembly in place with a slight forward pressure and use a
small tool to reach through the front panel to align the
buttons. Do not tighten the circuit-board securing screws
until the securing nuts at the front of the attenuator
chassis are tight and the circuit board is aligned properly.
Trigger Generator and Z-Axis Logic Board Removal.
Remove the board as follows:
1. 475 DM 43 and DM 40 only—Disconnect three
ribbon-cables from the DM 43 or DM 40 Main circuit
board. Remove two screws from the rear of the main
circuit-board chassis and separate the board chassis from
the instrument chassis.
2. Remove the LOW LINE, READY, and TRIG light
lenses. Pry them away from the front panel with a
fingernail and pull them straight out.
3. Remove the POWER extension shaft from the
power-switch plastic actuator. Use a small flat-blade
screwdriver to pry apart the coupling of the shaft and
actuator, using caution to prevent damage to the coupling.
4. Disconnect four ribbon-cables from the board as
directed in the following list.
a. Disconnect a four-wire cable near Q752 at the top of
the board (cable from B TRIGGER LEVEL control).
b. Disconnect a four-wire cable near J706, located two
inches below the cable previously removed (cable from A
TRIGGER LEVEL control).
c. Disconnect one-wire cable near the left end of J3 at
the bottom of the board.
d. Disconnect a five-wire cable from P644 at the
bottom, back of the board (cable from A TRIG HOLDOFF
control).
5. Disconnect eight coaxial cables from the front and
back sides of the board and confirm color coding of each
cable with its jack number in the following list. Record any
exceptions to this procedure for reference when
reassembling.
a. Cable to J704 is white with a blue stripe.
b. Cable to J702 is white with a green stripe.
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