Model 140A Section V
Paragraphs 5-28 to 5-38
5-28. If there is no high voltage output and none of c. Remove CRT bezel.
the filaments are lit, observe the waveform at the
d. Loosen clamp at socket of CRT.
collector of Q302 (blue wire). If an approximately
-1
30 kc 20-volt peak-to-peak sine wave appears for e. Remove socket of CRT by carefully prying
short intervals, the trouble is probably a defective loose.
component in the rectifier filter/divider networks.
f. Slide CRT forward out of instrument, keeping
If no waveform appears, use Table 5-5.
one hand on front face of CRT.
5-29. If the high voltage output is incorrect and
cannot be adjusted to the correct value, use Table 5-6. 5-36. To install CRT, reverse the above procedure.
Correct connection of leads at neck of CRT is shown
5-30. If the -2350 volt supply seems to be operating on the inside of bottom cover and in Figure 5-1.
properly, the +5 kv post-accelerator potential may
be checked by removing the left side instrument Note
cover and measuring the 5-kv voltage at the board
If a different CRT is installed, it will be
termination of the thick red lead.
necessary to: 1) Check trace alignment
with procedure given in Paragraph 3-7;
5-31. REPAIR AND REPLACEMENT.
2) Reset Geometry adjustment as described
5-32. AIR FILTER. in Paragraph 5-16; 3) Check plug-in cali-
bration.
5-33. Inspect the air filter at the rear of the instru-
ment and clean it before it becomes clogged enough
to restrict the flow of cooling air. To clean, remove
the filter from the instrument and wash it thoroughly
5-37. FAN MOTOR REMOVAL.
in warm water and detergent. Dry thoroughly and
coat with a filter adhesive such as Filter Coat No. 3 a. Disconnect the white-gray and white-green-gray
from Research Products Inc. This adhesive is wires from fan terminals at bottom of instrument.
available from heating supply stores or from your
Hewlett-? Ingineering Representative. b. Remove all four transistor heat sinks from the
fan assembly, and push out of the way.
5-34. REMOVAL OF CATHODE-RAY TUBE.
c. Remove the four nuts on rear panel which
5-35. It is recommended that a face mask or goggles
secure the fan assembly to instrument frame.
and gloves be used when it is necessary to handle
)
the CRT. To remove: d. Lift out fan assembly.
a. Disconnect post-accelerator lead. This can be e. Remove fan motor brackets.
done by lifting the edge of the rubber cap, and using
a screwdriver to compress the spring contact until
5-38. To install fan, reverse the above procedure.
it comes free.
When tightening the mounting nuts on the rear panel,
b. Disconnect leads at neck of CRT, taking care use long-nose pliers or similar tool to prevent
not to bend the pins. rubber shock mounts from twisting.
Table 5-5. Troubleshooting High Voltage Supply, No Voltage
1. Check Q302, L301, and the associated transformer primary for open circuits or shorts.
Replace any bad components.
Procedure I Indication 1 Conclusion
2. Remove the edge-on connector which goes to Rectifier (V302-V305) Proceed to step 3.
the emitter of Q301 (yellow wire). Connect filaments light.
this lead through a 2K resistor to -12.6 volts
Filaments don?t light. Proceed to step 4.
(any white-violet wire). I I
3. Replace edge-on connector, and change V301. I Filaments light. I Q301 was bad,
Filaments don?t light. Check biasing circuitry of
V301. Then check Q301 and
associated circuitry.
4. Check T301 and rectifier load circuit for Filaments light. Put capacitors back one at
opens or shorts. Then lift one lead of C313, a time until the bad one
C314, C315, C316, C317, C321, and turn causes filaments to go out.
instrument on again.
Filaments don?t light. Trouble probably with
transformer T301.
01638-1 5-7 |
ACEC
