TTB-9-2920-225-34-1 Regulator Check Out and Repair 100 Amp 2920-00-900-7993 Download
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TB 9-2920-225-34-1 Figure 1–1. 100 AMP regulator. 1-4. Removal and Installation. The regulator 1-5. Major Items Affected. Because of the nu- must be removed from the vehicle for testing and merous vehicles affected, a listing of the vehicles repair. The procedures given in this bulletin are will not be supplied. Check the regulator’s NSN for bench testing and repair only. Refer to the ap- (2920-00-900-7993) or part number (10947439) propriate vehicle manual for removal and instal- in section IV of your vehicle’s repair parts manual lation procedures for your particular vehicle. for applicability. Section II. FUNDAMENTALS OF SOLID STATE COMPONENT CHECKOUT AND REPAIR 1-6. Introduction. a. Checkout and repair of solid state voltage regulators involves techniques dif- ferent from those employed with mechanical volt- age regulators. b. Before attempting checkout and repair of solid state voltage regulators, follow the instruc- tions of paragraphs 1–7 and 1–8, 1-7. Meters. a. The type of meter used to check- out solid state components is critical and should be limited to quality meters such as the TS-352 or the Simpson 260 multimeters, or their equivalent. When using an ohmmeter with unknown technical specifications or characteristics, the following checks can be made to determine if the ohmmeter scales will cause damage to low power transistors. (1) Check the voltage across the ohmmeter leads as the ranges are switched. No scale should be used if the voltge exceeds 3 volts. (2) If the instrument is a combination volt- ohmmeter, the positive voltmeter lead may not be the positive ohmmeter lead. The polarity of the ohmmeter leads must be known. Polarity can be determined by connecting the ohmmeter to a voltmeter. If the voltmeter moves up scale the ohmmeter has the same polarity as the voltmeter. 1-2 If the voltmeter attempts to move down scale the ohmmeter leads have opposite polarity, e.g., TS– 352 multimeter. If necessary mark the ohmmeter leads positive and negative for reference. b. The ohmmeter readings obtained when check- ing semiconductor devices depends on the internal makeup of the meter, scale used, type of transistor and its temperature. Therefore, exact resistance readings are seldom given. Readings are usually referred to as low resistance, which is less than 20 ohms; and high resistance which is more than 200 ohms. Occasional failures may occur which can be detected by these tests. If readings obtained are doubtful or operation of the regulator is not proper, replace the transistors. 1-8. DOs AND DON’Ts For Circuit Repair. a. DO—When replacing solid state circuit boards, clip the connecting wires, leaving a small portion of wire with insulation to act as a refer- ence for connecting points on the replacement board. b. DON’T—Attempt to interchange circuit boards between regulator models. c. DO—Use high quality resin core solder of 60–40 tin lead composition.