CHAPTER 3. DIRECT SUPPORT MAINTENANCE

TM 11-6760-238-34

CHAPTER 3

DIRECT SUPPORT MAINTENANCE

Section I. DIRECT SUPPORT TROUBLESHOOTING

troubles is started with the troubleshooting procedures

WARNING

provided in Operator's and Organizational Maintenance

When troubleshooting or making repairs

Manual, TM 11-6760-238-12.

on Test Set, Control Panel, Focal Plane

c. Localization Checks. After the trouble has been

Shutter LS-78A, be extremely careful.

sectionalized, perform operational check (para 3-5) of

Use insulated test probes when making

the shutter test set. The operation check serves as a

the required voltage measurements.

check of the localization technique In addition,

Always disconnect the power cord from

assemblies or subassemblies, in some cases parts, can

the test panel before touching any of the

be localized within the shutter test set by the methods

internal parts Ground all points of high

listed (1) through (3) below.

potential to ensure any residual voltages

(1) Visual inspection. The purpose of visual

are removed. Make certain that you are

inspection is to locate faults without testing or measuring

not

grounded

when

making

circuits or components. All visual signs should be

measurements or adjustments inside the

analyzed to help locate the fault to a' particular

test set.

Do not deviate from

subchassis, stage, or part. Mechanical faults are most

recommended procedural steps.

often localized through visual inspection

3-1. General Instructions

(2) Pluck-out parts. Defective pluck-out

Troubleshooting at the direct support

parts will be the cause of many troubles. Remove and

maintenance level includes all the techniques outlined for

test all pluck-out parts suspected of being faulty.

organizational maintenance and any special or additional

Replace each defective part with an identical part known

techniques required to isolate a defective part. The

to be good.

maintenance procedures are not complete in themselves

(3) Troubleshooting table. The malfunctions

but supplement the procedures outlined in

listed in the troubleshooting table (para 3-6) will aid

Operator's and Organizational Maintenance Manual (TM

localizing trouble to a component part, subassembly, or

11-6760-238-12).

assembly.

b. Troubleshooting may be performed while the

d. Isolation Checks. Isolation checks for individual

test panel is operating or if necessary, after the

assemblies and subassemblies will not be performed at

equipment (or parts of it) has been removed from

the direct support maintenance level. Defective parts

service. When trouble occurs, certain observations and

can be isolated by the methods listed in (1) through (2)

measurements can be made that will help to determine

below.

the source of trouble Usually, when troubleshooting is

(1) Voltage and resistance measurements.

performed while the shutter test set is operating, it is

This equipment is transistorized. Observe all cautions

done at the organizational level (TM 11-6760-238-12).

given to prevent transistor damage. Make voltage and

3-2. Organization of Direct Support

resistance measurements in this equipment only as

Troubleshooting Procedures

specified in table 3-2. Use resistor and capacitor color

General.

Three steps are used in

codes (FO-8) to find value of components.

troubleshooting equipment. They are. Sectionalization,

(2) Intermittent troubles. In all tests, the

localization, and isolation.

Sectionalization means

possibility of intermittent troubles should not be

tracing the fault to the major unit. Refer to TM 11-6760-

overlooked. If present, this type of trouble often may be

238-12 for sectionalization procedures. Localization

made evident by tapping or jarring the front panel.

means tracing the fault to the defective section or stage

Check the wiring and connections to the assemblies and

within an assembly or subassembly. Isolation means

subassemblies of the shutter test set.

tracing the fault to the defective part. Some faults can

often be isolated by sight, touch, or hearing The majority

3-3. Test Equipment and Tools Required

of faults, however, must be isolated by detailed electrical,

Table 3-1 below lists the tools and test equipment

mechanical, and electronic checks.

required for troubleshooting and repair of the test panel

b. Sectionalization Checks. Sectionalization of

3-1