Tektronix 442, Инструкция по эксплуатации

Страница: 91 / 170

Maintenance—442 Service
3. Remove the High Voltage Caution shield (four
Phillips-head screws) from the Interface board.
W A R N I N G
I
The crt anode and the output terminal of high-
voltage multiplier U460 may retain a 10,000 volt
charge after the instrument is turned off. To avoid
electrical shock, ground both the output terminal of
U460 and the crt high-voltage anode lead to chassis
ground.
4. Ground the U460 high voltage multiplier output
terminal and the crt anode lead to chassis
ground. Disconnect the anode lead from the
U460 output terminal. Dress the anode lead so it
will clear all chassis parts and can be removed
along with the crt and shield assembly in the
following steps.
NOTE
In the following steps 5 through 8, make a note of all
wire color codes, connection location and connec­
tor orientation, for re-assembly reference.
5. Disconnect the horizontal deflection plate pin
connectors from the crt neck pins.
6. Disconnect both ends of the vertical deflection
plate lead pin connectors (from the crt neck pins
and from the Interface board at P I38 and P148).
7. Disconnect P470 (four pins, two separate 2-pin
plugs) from the Interface board.
8. Disconnect P2332 from the A14 Horizontal Out­
put board (the A14 board will be removed from
the instrument along with the crt and shield
assembly in the following steps).
9. Remove the three screws that secure the delay
line tie-down straps to the rear crt bracket (see
Figure 5-8). Lay the delay line so it will clear the
crt shield.
10. Remove the four screws that secure the rear crt
bracket to the chassis near the crt base.
11. Support the crt shield assembly while removing
the two screws that secure the crt front support
plastic mounting bracket to the inside of the 442
front panel casting. These two screws are the
ones closest to the bottom of the crt graticule.
The two screws nearest the top of the crt graticule
may be left in place.
12. Slide the plastic support bracket slightly in the
direction of the bottom of the crt graticule to
releasethe plastic support bracketfromthelipon
the metal clip (bracket) near the top of the crt
graticule.
13. Slide the crt shield assembly toward the back of
the 442; then tilt the neck support bracket toward
the bottom of the 442 and tilt the crt faceplate end
of the shield toward the top of the 442. Next, slide
the entire crt and shield assembly away from the
442 chassis in the direction of the bottom of the
instrument.
14. Carefully slide the crt and anode lead forward out
of the shield. Note orientation of the anode lead
(top right corner) and ground spring contact
(bottom front) for re-assembly reference.
15. To re-install the crt in the shield assembly,
carefully slide the crt and anode lead into the
shield and guide the crt so the base passes freely
through the trace rotation coil.
16. To re-install the crt and shield assembly in the
442, reverse the order of the foregoing steps.
Before using any test equipment to make meas­
urements
on static-sensitive components or
assemblies, be certain that any voltage or current
supplied by the test equipment does not exceed the
limits of the component to be tested.
5-22
REV A MAY 1980