All paragraph references in the troubleshooting chart (fig. 2-4) are for TM 11-6740-281-12. The paragraph
references do not match with this lesson although all the material is covered.
4.
Sectionalization
a. General electrical checks.
(1) Perform continuity tests of the suspected circuit wiring. If an electrical wire is open or two or
more wires are shorted, refer the printer to the next higher level of maintenance.
(2) Check the motors for open or shorted windings. If a motor is found to be defective, refer the
defective motor to the next higher category of maintenance.
(3) Check the lighted pushbuttons, switches, lamps, and relay coils for open or shorted
conditions. Replace lighted pushbuttons, switches, and lamps. If a relay is found to be defective, refer to a
higher category of maintenance.
b. Short circuit.
(1) DISCONNECT THE POWER CABLE FROM THE SOURCE.
(2) Remove the cover from the top of the control unit by removing 11 screws and washers from
the top and 5 screws and washers from the rear of the cover.
(3) Disconnect the power cable from pins 1 and 2 at terminal board TB1.
(4) Measure the resistance between the leads of the power cable. It should read infinite.
(5) Measure the resistance between terminal board pins 1 and 2 with the power cable
disconnected and with the POWER pushbutton set to OFF. It should read infinity. If a short is indicated,
wires attached to the terminal board are shorted. If defective wiring is causing the short circuit, refer the
trouble to the next level of maintenance.
(6) Reconnect the power cable to the terminal board, replace the control unit cover and secure
with 16 screws and washers.
c. Open circuit.
(1) DISCONNECT THE POWER CABLE FROM THE SOURCE.
(2) Remove the cover from the top of the control unit by removing 11 screws and washers from
the top and five screws and washers from the rear of the cover.
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