Section IV. OPERATIONAL CHECKOUT - TM-55-4920-425-13-P0015

TM 55-4920-425-13&P

3-7. Cleaning. The only internal cleaning required is cleaning of the slip rings (refer to fig 3-2). The slip rings should

be thoroughly cleaned with cleaning solvent (Item 2, Table 1-1) and wiped dry with clean cloths. Remove dirt from

exterior surfaces with mild detergent and hot water solution. Rinse thoroughly until all traces of detergent are removed

Dry with compressed air or a clean cloth.

Section IV. OPERATIONAL CHECKOUT

3-8. Performance Checks.

a. Rotation Direction. Check to see that the table rotates in the clockwise direction when the rotation switch

indicates CW. Check also to see that the table rotates in the counter-clockwise direction when the switch indicates CCW.

b. Vibrator Operation. Turn VIBRATOR switch to the ON position and check to see that the vibrator motor is

running. Vibration may be felt on any part of the table or cradle.

c. Rate of Turn. Check rate of turn for each setting of the DEG/SEG switch with the aid of a stop watch while

observing the table scale at the table index.

d. Electrical Transfer Circuit. With an ohm meter or continuity tester, check for continuity between corresponding

pin numbers of connectors on the rim of the table and matching connectors on the rear plate of the cradle (refer to fig. 3-

3). Each of the fourteen circuits should be checked. With the CLUTCH switch in the OFF position, the table may be

rotated to check continuity around each section of the slip ring. If discontinuity occurs, refer to Table 3-1.

e. Rate Of Turn. Should the rate of turn (in any one of the selected speeds) not meet specifications, it may be

adjusted in the following manner. Tilt the cradle to its 90 degree position and remove the base cover as in paragraph 3-

4. With a 7/16 open end or box wrench, loosen the hex locking nut on the proper potentiometer (refer to fig 3-4) and

adjust the speed with a screwdriver until it is correct. Make sure the speed control on the front panel is set to the speed

to be adjusted and the table is running in either direction. At a speed of 20 degrees per second the table should make

exactly one revolution in 18 seconds. At a speed of 15 degrees per second the table should make one revolution 24

seconds and at a speed of 10 degrees per second the table should make one revolution in 36 seconds. After the speed

is set properly, lock the position by tightening the potentiometer lock nut while holding the shaft with the screwdriver.

Recheck the speed after tightening the lock nut to make sure it has not shifted during the tightening operation.

f. Low Voltage Relays. The low voltage relay (refer to fig 3-4) provides an automatic power cutoff to the instrument

if the line voltage drops below 108 volts. This protects the instrument as well as any other unit connected to the same

power source through the instrument. The two knobs at one end of the relay adjust the cut-off voltage and the differential

between off and on. They are properly set at the factory and need no further adjustment.

3-9. Troubleshooting . Most troubles or failures may be tracked to a defective part or to an improper adjustment.

Refer to Table 3-1 and Figure 3-5 for other troubles.

Section V. REPAIR AND REPLACEMENT OF AUTHORIZED PARTS

3-10. Disassembly. The instrument may be easily disassembled by standard methods and without the use of special

tools. Refer to Figures 3-7, 3-8, and 3-9. Inspection of components may be done with disassembly. Figures 3-4 and 3-6

shows the interior views of the instrument.

3-11. Cradle Assembly. (Fig 3-7).

a. Remove line cord from power source and from rear connector on the base. Remove motor cable from the

connector on rear of cradle and from the connector on the rear of the base.

b. With the cradle in its upright position (table horizontal), remove eight screws and cradle front cover (39)

c. Using a 5/64 hex key wrench remove screws (46, 49, 52, 55, 58) and lock washer (47, 50, 53, 56, 59) from the

five connectors (57, 54, 51, 48, 45) on the cradle rear cover. Do not stretch, break, or damage attached electrical wiring.

d. Remove eight screws (61) and cradle rear cover (60).

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