Tektronix 455, Instruction Manual, Page: 84 / 246

Maintenance—4 5 5 /A 2 /B 2
A and B Timing Switch Board Removal
To remove switch assembly:
1. Set A and B T IM E /D IV knobs to .2 ps.
2. Remove VAR and A and B T IM E /D IV knobs using
hex wrench.
3. Remove the tw o screws and hex nuts holding switch
board assembly to Horizontal board, see Fig. 5-11.
4. Unplug switch board assembly from Sweep board.
D o n o t touch sw itch contacts; they can be easily
damaged o r contam inated. I f cleaning is neces­
sary, use a s o ft camel-hair brush and iso p ro p yl
alcohol. A d o th w ith a lco h ol m ay be used on
board contacts.
To reassemble Timing Switch board:
1. Sandwich the switch mechanism between A and B
Timing boards as shown; A board at fro n t (shaft end) and
B board at rear. Install plastic mounting clip in place
between boards.
To separate A and B tim ing boards (Fig. 5-11).
1. Remove VAR control shaft at coupling using hex
wrench.
2. Remove fo u r screws holding A and B Timing Switch
boards together. Separate boards, being careful not to
lose plastic mounting clip.
2. Secure the boards w ith fo ur screws as shown. Make
sure locator keys are seated in boards before tightening
screws.
3. Install VAR control shaft.
4. Plug Timing board assembly onto Sweep board. Be
careful not to bend pins.
Fig. 5-11. A and B timing switch disassembly.
5-12
REV. A, OCT 1975