Chapter 7. DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE INSTRUCTIONS

TM 32-5895-227-14&P

CHAPTER 7

DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE INSTRUCTIONS

Section I. GENERAL

Equipment

Manuals

7-1 SCOPE. Direct support and general support

maintenance consists of sectionalizing, localizing, and

Teletypewriter Set AN/TGC-14

TM 11-5815-206-12

isolating equipment faults, malfunctions, and problems,

and making the necessary repairs based on the findings.

7-2 FUNCTIONAL DIAGRAMS. Location diagrams

General techniques are provided, followed by

troubleshooting charts for specific equipment in the

show the components that are used to perform a

baseline configuration. Equipment covered in other

particular function. Wiring diagrams show the electrical

manuals is listed below.

function of the components in the system. These

diagrams are integrated with and referenced in the

Equipment

Manuals

troubleshooting procedures.

Radio Receiver R-390A/URR

TM 11-5820-358-35

Antenna Coupler CU-872A/U

NAVSHIPS 94490

Section II. TOOLS AND EQUIPMENT

d. The equipment power supply normally used is

7-3 TEST EQUIPMENT. Test equipment required for

recommended as the source of power when servicing

troubleshooting is listed below.

transistorized equipment. Observe polarity. Polarity

reversal may damage the transistors as well as

Equipment

NSN

electrolytic capacitors in the circuit. If a different power

Multimeter AN/USM-223

6625-00-999-7465

supply is used in place of the power supply normally

Audio Signal Generator

6625-00-788-9672

used with the equipment, it must have good voltage

AN/USM-205

regulation and low ac ripple.

Good regulation is

Oscilloscope (Tektronix 321A)

important because the output voltage of a poorly

regulated supply may exceed the maximum voltage

7-4 PRECAUTIONS.

Observe the following

rating of the transistors in the equipment being tested.

precautions:

A power supply that has poor ac filtering will create a

a. The AN/MSQ-71 equipment contains transistor

false indication of poor filtering in the equipment being

circuits. If any equipment item does not have an

tested.

isolation transformer in its power supply circuit, connect

e. The transistorized equipment must be turned

one in the power input circuit.

off before switching the power supply on or off. The

b. Never connect test equipment (other than

transient voltages, created by turning the test power

suitable multimeters and VTVM's) outputs directly to a

supply on and off, may exceed the maximum rating of

transistor circuit. Use a coupling capacitor.

the transistors. Also, be cert: tat' a normal load is

c. Make test equipment connections with care so

connected to the transistorized equipment before

that shorts will not be caused by exposed test equipment

applying power.

connectors. Tape or sleeve (spaghetti) test probes or

clips, as necessary, to make contact with the circuit

under test.

Section III. TROUBLESHOOTING AND MAINTENANCE OF THE AN/MSQ-71

resistors or arcing and shorted transformers, can often

7-5 GENERAL. The first step in servicing a defective

be located by sight, smell, or hearing. Most faults,

system is to sectionalize the fault, tracing the fault to a

however, must be isolated by checking voltages and

major component. The second step is to localize the

resistances.

fault, tracing the fault to a defective part responsible for

the abnormal condition. Some faults, such as burnt-out

7-1