Section III. RADIO INTERFERENCE SUPPRESSION

TM 10-3930-609-35

for voltage drop to zero after the battery switch is closed

2-9. Test of Fl Filter and SCR Firing Circuits.

is much less or greater than one second, adjust 1A

TIME trimpot to obtain approximately one second timer

Both the filter and SCR firing circuits contained in filter

action. A finer adjustment may be made later, if

F1 (fig. 2-2 and 2-3) can be tested with an ohmmeter. -

necessary, during a checkout of truck performance.

Disconnect battery and filter leads as required for the

tests.

Note

The timer controls the delay in the

a. Test of 5 REC Firing Circuit. Disconnect lead to

pick up of relay 1A, which cuts out

terminal 7 of F1. With ohmmeter set to RX100 range,

the SCR control system and applies

connect positive lead to terminal 8 and negative lead to

full battery voltage to the travel

terminal 7. The resistance reading should be between

motor for full-speed operation. This

1,700 and 2,100 ohms. With the leads reversed an

occurs when the accelerating control

infinity reading should be obtained.

is fully depressed to close switch

b. Test of 2 REC Firing Circuit. Disconnect lead to

ASA2. If the timer closes relay 1A

terminal 5 of F1. With ohmmeter set to RXi00 range,

too early, truck operation will be

connect positive lead to terminal 6 and negative lead to

jerky; if timer closes 1A too late,

terminal 5. The resistance reading should be between

truck operation will be sluggish.

1,170 and 1,430 ohms. With the leads reversed an

infinity reading should be obtained.

(4) If the timer does not operate at all, or

c. Test of Transformer Filter. Disconnect lead to

cannot be adjusted properly with the 1A TIME trimpot,

terminal 4 of F1. With ohmmeter set to RX100 range,

replace Card 1.

connect positive lead to terminal 6 and negative lead to

terminal 4. The resistance reading should be between

2,050 and 2,750 ohms. With the leads reversed an

infinity reading should be obtained.

d. Allowing for Meter and Reading Errors. If any

reading in the three preceding tests on F1 is definitely

outside the specified values, filter F1 should be

replaced.

Figure 2-6. Test circuit for times section of card 1.

Section III. RADIO INTERFERENCE SUPPRESSION

2-10. General

Refer to TM 11-483 for definitions, purposes, source and

methods used to obtain proper radio suppression.

2-11.

Testing of Radio Interference Suppression

Components

If the radio suppression component is suspected of

being defective, proceed as follows:

a. Disconnect leads 13A-1 and 84 from screw-type

terminals on component.

b. Take out two screws, flatwashers, and

lockwashers which secure component to master cylinder

support to remove component.

c. Check component on a capacitor tester for leak

and short. Replace component if defective.

Figure 2-7. Interference, suppre8sion component,

removal and installation.

2-11