Tektronix 442, Instruction Manual

Page: 90 / 170

Maintenance—442 Service
3. Unsolder or unplug all cables and wires that
connect from the Trigger board to other
assemblies (note locations for re-assembly
reference).
4. Disconnect fixed connector P2100ontheTrigger
board from J2100 on the Horizontal board by
carefully lifting the Trigger board away from the
Horizontal board; then lift the Trigger board
toward the back of the 442 so the switch knobs
clear the front panel openings.
5. To re-install the Trigger board and HOLD OFF
control, reverse the order of the foregoing steps.
A12 Horizontal Board Removal
To remove the Horizontal board from the 442, first
move the Interface board to the access position (see A1
Interface Board Removal). Then remove the Trigger
Switch board from the 442 (see A11 Trigger Switch Board
Removal). With that accomplished, proceed as follows:
1. Use a 1/16” Allen wrench to remove the SEC/DIV
and SEC/DIV VAR knobs. Disconnect the LEVEL
and Horizontal POSITION shaft/knobassemblies
from the potentiometer shafts and remove the
shaft/knob assemblies out through the front
panel openings.
2. Disconnect all single and multi-pin connectors
from either the Horizontal board or the board
where the connector attaches (depending on
which end has soldered connections). Note the
location of these connections for re-assembly
reference.
3. Remove the six Phillips-head screws that secure
the Horizontal board to the 442 chassis (see Fig­
ure 5-9).
4. Guide the Horizontal board away from the front
panel and chassis so the control buttons and
shafts clear the front panel openings.
5. To re-install the Horizontal board, reverse the
order of the foregoing steps.
A13 Timing Board (SEC/DIV Switch) Removal
The Timing board is plugged into two connectors on
the A12 Horizontal board. To remove the Timing board,
first move the Interface board to the access position (see
A1 Interface Board Removal), then proceed as follows:
1. Disconnect the Horizontal POSITIONshaft/knob
assembly from the potentiometer shaft and pull
the assembly far enough out through the front
panel opening to clear the hole in the Timing
board.
2. Use an Allen wrench to disconnect the SEC/DIV
VAR shaft from the coupling that fastens it to the
potentiometer and pull the SEC/DIV VAR knobto
remove the shaft out from the SEC/DIV shaft.
3. Use a 1/16" Allen wrench to remove the SEC/DIV
knob.
4. Lift the Timing board away from the Horizontal
board and toward the back of the 442 so it
disconnects from the two connectors and the
SEC/DIV shaft clears the front panel opening.
5. To re-install the Timing board, reverse the order
of the foregoing steps.
Cathode Ray Tube (crt) Removal
W A R N I N G
I
Use care when handling a cathode ray tube. Protec­
tive clothing and safety glasses should be worn.
Avoid striking the cathode ray tube on any object
that could cause it to crack or implode. When storing
a cathode ray tube, place it in a protective carton or
set it face down on a smooth surface in a protective
location with a soft mat under the faceplate to
protect it from scratches.
To remove the crt, temporarily reassemble the rear
cabinet frame and four feet to the rear panel with the
Phillips-head foot securing screws. Position the 442 with
the crt faceplate facing upward and the chassis supported
by the rear feet. Rotate the instrument as required in the
following steps and proceed as follows:
1. Move the Interface board to the access position
(see A1 Interface Board Removal).
2. Disconnect the socket from the crt base.
REV A MAY 1980
5-21