Section V Model 140A
Paragraphs 5-39 to 5-42
Table 5-6. Troubleshooting High-Voltage Supply, Incorrect Voltage
Procedure Effect Conclusion
~~~ ~~~
1 1. Remove Nuvistor V301 from its socket. Output drops to zero. Proceed to step 2..
Output remains at an 1 Q301 shorted
incorrect value.
2. Replace V301 in its socket, and lift one Output drops. Trouble probably in the
end of R301. resistor divider network
R311, R325, R326, R327,
R328, R329, R318, and
R319
Output remains at an V301 bad.
incorrect value.
5-39. REMOVAL OF HIGH-VOLTAGE ASSEMBLY. DISCONNECT
POST-ACCELERATOR
a. Disconnect the six leads identified in Figure 5-3.
b. Disconnect post-accelerator lead as described
in Paragraph 5-35a. R
c. Remove the four screws identified in Figure 5-3. S 9
d. Tip assembly away from left side of instrument
and lift out from top.
5-40. To install high-voltage assembly, reverse the
above procedure.
5-41. SERVICING ETCHED CIRCUIT BOARDS.
5-42. Etched circuit boards used in the Model 140A
have components on one side of the board witha
plated conductive layer of metal through component
holes. @ Service Note M-20D also contains useful
information on etched circuit repair. The impor- WHT-RED -YEL
tant steps and considerations are:
a. Use a low heat (37 to 47.5 watts, less than 800°F
idling temperature), slightly bent chisel tip (1/16 to
1/8 inch diameter) soldering iron, and a small dia-
meter, high tin content solder. If a rosin solder is
used, clean the area thoroughly after soldering.
b. Components may be removed by placing the
soldering iron on the component lead on either side 140A-0-1
of the board, and pulling up on the lead. If heat is Figure 5-3. Removal of High-
applied to the component side of the board, greater
care is required to avoid damage to the component Deck Assembly
(especially true for diodes). If heat damage may
occur, grip the lead with a pair of pliers to provide from the board. A conductor may be cemented back
a heat sink between the soldering iron and component.
in place with a quick-drying acetate base cement (use
c. If a component is obviously damaged or faulty, sparingly) having good issulating properties. Another
clip the leads close to the component and thenun- method for repair is to solder a section of good con-
solder the leads from the board. ducting wire along the damaged area.
d. Large components such as potentiometers and f. Clear the solder from the circuit board hole
tube sockets may be removed by rotating the soldering before inserting a new component lead. Heat the
iron from lead to lead and apply steady pressure to solder in the hole, remove the iron, and quickly
lift the part free (the alternative is to clip the leads insert a pointed non-metallic object, such as a
of a damaged part). toothpick.
e. Since the conductor part of the etched circuit g. Shape the new component leads and clip to
board is a metal plated surface, covered with solder, proper length. Insert the leads in the holes and apply
use care to avoid overheating and lifting the conductor heat and solder, preferably on the conductor side.
5-8 01638-1 |
ACEC
