Section II. FUNDAMENTALS OF SOLID STATE COMPONENT CHECKOUT AND REPAIR

TB 9-2920-225-34-1

100 AMP regulator.

Figure 11.

1-4. Removal and Installation. The regulator

1-5. Major Items Affected. Because of the nu-

merous vehicles affected, a listing of the vehicles

must be removed from the vehicle for testing and

repair. The procedures given in this bulletin are

will not be supplied. Check the regulator's NSN

(2920-00-900-7993) or part number (10947439)

for bench testing and repair only. Refer to the ap-

in section IV of your vehicle's repair parts manual

propriate vehicle manual for removal and instal-

for applicability.

lation procedures for your particular vehicle.

Section II. FUNDAMENTALS OF SOLID STATE COMPONENT CHECKOUT AND REPAIR

If the voltmeter attempts to move down scale the

1-6. Introduction. a. Checkout and repair of solid

ohmmeter leads have opposite polarity, e.g., TS

state voltage regulators involves techniques dif-

352 multimeter. If necessary mark the ohmmeter

ferent from those employed with mechanical volt-

leads positive and negative for reference.

age regulators.

b. The ohmmeter readings obtained when check-

b. Before attempting checkout and repair of

ing semiconductor devices depends on the internal

solid state voltage regulators, follow the instruc-

makeup of the meter, scale used, type of transistor

tions of paragraphs 17 and 18,

and its temperature. Therefore, exact resistance

1-7. Meters. a. The type of meter used to check-

readings are seldom given. Readings are usually

out solid state components is critical and should

referred to as low resistance, which is less than 20

be limited to quality meters such as the TS-352 or

ohms; and high resistance which is more than 200

the Simpson 260 multimeters, or their equivalent.

ohms. Occasional failures may occur which can

When using an ohmmeter with unknown technical

be detected by these tests. If readings obtained are

specifications or characteristics, the following

doubtful or operation of the regulator is not

checks can be made to determine if the ohmmeter

proper, replace the transistors.

scales will cause damage to low power transistors.

1-8. DOs AND DON'Ts For Circuit Repair.

(1) Check the voltage across the ohmmeter

a. DO--When replacing solid state circuit

leads as the ranges are switched. No scale should

boards, clip the connecting wires, leaving a small

be used if the voltge exceeds 3 volts.

portion of wire with insulation to act as a refer-

(2) If the instrument is a combination volt-

ence for connecting points on the replacement

ohmmeter, the positive voltmeter lead may not

board.

be the positive ohmmeter lead. The polarity of the

b. DON'T--Attempt to interchange circuit

ohmmeter leads must be known. Polarity can be

boards between regulator models.

determined by connecting the ohmmeter to a

c. DO--Use high quality resin core solder of

voltmeter. If the voltmeter moves up scale the

6040 tin lead composition.

ohmmeter has the same polarity as the voltmeter.

1-2