CHAPTER 3. DIRECT SUPPORT MAINTENANCE

TM 11-5820-509-35

CHAPTER 3

DIRECT SUPPORT MAINTENANCE

Section I GENERAL TROUBLE SHOOTING TECHNIQUES

c. Sectionalizing. The AN/PRC-47 consists of a

WARNING

receiver-transmitter, storage batteries, antenna systems,

handset, headset, telegraph key. loudspeaker, and

Avoid contact with the high-voltage

interconnecting cables.

In all probability the

circuits and the antenna terminal of

organizational level will have eliminated most of the

the radio transmitter-receiver while

accessory items as possible trouble sources and the

performing

trouble

isolation

receiver-transmitter will remain for the direct support

procedures:

personal injury may

maintenance technician. Substitution of a suspected

result.

accessory item or a receiver-transmitter subassembly

(module} with one of known integrity will often eliminate

3-1. Scope

a tedious series of detailed checks and measurements.

a. General.

The troubleshooting procedures

The operational tests described in the intermediate

outlined in this section are to be performed at the direct

preventive maintenance checks and services portion of

support (DS) maintenance level.

Complete

TM 11-5820-509-12 will aid the maintenance technician

troubleshooting procedures for the radio set beginning at

to sectionalize the source of trouble at this maintenance

the operational level which are described in TM 11-

level.

5820-509-12.

The operational tests listed in the

preventive maintenance checks and service charts

d. Localizing.

Once the trouble has been

enable the organizational maintenance technician to

sectionalized to a functional unit or group of circuits, the

sectionalize some types of malfunction to specific

next step is to localize it to a specific circuit within this

functional units of the radio set. Additional test facilties

area. In the case of the receiver-transmitter, the steps

and special maintenance equipment are available at the

required to isolate the malfunction are relatively difficult

direct support level that provide more conclusive test

because of the complexity and interdependency of the

results for sectionalizing the problem within a unit.

circuits involved. These steps are supplemented by the

Once the trouble has been sectionalized, the functional

following general procedures.

nature of the problem (whether audio, control, etc) will

enable the maintenance technician to further isolate the

malfunction to a particular circuit or component. When

(1) Observation. Observation involves a thorough

the sectionalizing test results indicate a malfunction

understanding of the receiver-transmitter, circuits and

within the receiver-transmitter subassembly, the delayed

may include such subjects as whether the fault occurs

trouble-iso1ation procedures shown in Section II should

only during the transmit mode, whether the problem

be observed.

occurs only at certain frequencies, or whether the

problem occurs only in the voice mode.

b. Organization. The first step in servicing a

defective radio set is to sectionalize the fault to a

(2) Troubleshooting Chart.

The troubleshooting

specific unit or section of the equipment. In complex

charts contained in Section II assist the technician in

equipments consisting of more than one functional unit

performing bench tests on the radio.

The

or inter-related circuitry, the fault must first be isolated

instrumentation used for the bench tests assists the

to a specific unit or group of circuits within a functional

technician in performing operational evaluation of the

unit. Once this has been accomplished, isolation to a

equipment without providing cumbersome antennas and

specific circuit and then to a component level may be

difficult test setups.

pursued. It is seldom possible to observe a symptom,

diagnose the cause, and immediately locate the

(3) Special Tests.

Special tests including

defective part unless a part shows obvious physical

resistance and continuity measurements, signal tracing

damage.

Generally it is necessary to perform a

techniques and signal waveform displays

sequence of operational checks, observations, and

measurements before the problem components are

isolated. This sequence of steps is called sectionalizing,

localizing, and fault isolation.

3-1