Section VI. TROUBLESHOOTING AND PARTS REPLACEMENT

C1, TM 11-6625-646-15

SECTION VI

TROUBLESHOOTING AND PARTS REPLACEMENT

6-5. Parts Replacement

6-1. Troubleshooting Procedures

6-2. General

6-6. Test set components are accessible when the

During

troubleshooting,

observe

the

following

panel-chassis is removed from its case. Except for

precautions and procedures:

items in paragraphs 6-7 through 6-11, all components

can be replaced without special instructions.

a. Perform continuity checks with all electrical

power OFF.

6-7. Replacement of Air Pump Assembly

b. Unless otherwise specified, measure voltages to

(fig. 6-5)

ground (chassis) with a 20,000-ohm-per-volt multimeter.

Replace the air pump assembly as follows:

c. When unsoldering and removing parts such as

a. Remove the panel-chassis from its case.

meters or rotary switches, note carefully the position of

b. Disconnect the plumbing and the electrical wires

the connecting wires. Tag each wire before unsoldering.

from the pump.

d. When replacing components, installed on the

c. Remove the defective pump.

underside of the test set chassis, be careful not to

loosen wires or damage adjacent components.

d. Refer to TM 11-6625-614-45 for repair of the air

pump assembly.

e. Solder connections carefully; poorly soldered

connections can result in intermittent operation.

e. Install the replacement pump.

f. When soldering wires to the test meters, use a

f. Comment the plumbing to the pump. Connect

heat sink and a soldering iron with a rating of not more

the electrical wires.

than 40 watts.

g. Check pump operation to ensure it is functioning

g. When removing or installing a printed-wiring

properly.

card, be careful not to damage components on the card

h. Reinstall the panel-chassis in the case.

or those on adjacent cards.

6-8. Replacement of Regulator Valves

6-3. Test Equipment Required

Replace the regulator valve as follows:

Refer to paragraph 7-3.

a. Remove the control knob from the valve shaft.

b. Remove the panel-chassis from its case.

6-4. Troubleshooting Tables

c. Remove the bottom pan from the chassis.

Three troubleshooting tables are included to enable the

d. Disconnect the plumbing from the valve.

electronic technician to locate and correct trouble in the

test set. Table 6-1 covers all the test meter circuits.

e. Remove the attaching hardware from the valve

Table 6-2 covers the internal and external card test

and withdraw the valve from the chassis. Discard the

circuits.

Table 6-3 covers the miscellaneous test

faulty valve and gasket; retain the hardware.

circuits. Use the schematic diagrams (figs. 1-2 through

1-7), and the wiring diagrams (figs. 6-1 through 6-4), as

aids during troubleshooting.