TM5-6115-585-34NAVFAC P-8-623-34TO-35C2-3-455-2TM-05684C/05685B-34CHAPTER 8MAINTENANCE OF GENERATOR ASSEMBLYSection I. DESCRIPTION AND FUNCTION8-1.GENERAL.Refer to Operator and Organizational MaintenanceManual for description and function of the generator.Section II. MAINTENANCE8-2. GENERATORMAINTENANCE.a. Test (On Equipment) (see figure 8-1) On generators equippedwith the Acoustic Suppression Kit (ASK), the ASK cover assemblymust be removed for inspection and repair and replaced after comple-tion of task. Refer to Operator and Organizational MaintenanceManual for removal and installation of ASK cover assembly.(1) Isolate the trouble to generator or regulator. Disconnectthe voltage regulator at the exciter (wires P67C16 at TB3-5 andP60E16 at TB3-6). Connect a 12 volt battery in place of theregulator with the (+) terminal to TB3-6 and (-) terminal to TB3-5.Run the engine with the battery in place of the voltage regulator. Ifthere is output now, the voltage regulator is bad. If there is nooutput, the main alternator is bad.(2) Check generator operation. Run the set withoutan external load, if the engine appears to be loaded(dark smoke apparent) the generator may have a wind-ing short to ground. If the engine does not seem to beloaded, there may be open windings.(3) Testing Diodes (see figure 8-1). A shorted oropen diode in the rotating rectifier assembly cancause bad generator operation. This is evident byfailure of the generator terminal voltage to build upto rated value or a terminal voltage that is too low.When these symptoms are noticed, and the more ob-vious sources of trouble, (1) and (2) above have beeneliminated, check the individual diodes of the rotatingrectifier assembly as follows:(a) Loosen four screws (5) and rotate bellcover (7) until it can be removed over screw heads.(b) Disconnect each diode (42) by removingnuts and washers (40 and 41).(c) Use an ohmmeter to measure the resis-tance between the terminal end and the threaded base(heat sink) end of the diode. Reverse ohmmeter leadsand repeat the resistance measurement. A diode ingood condition will have a very high resistance forone measurement and a resistance near zero whenohmmeter probes are reversed. Failure to obtainthese two extremes in resistance measurement in-dicates a defective diode that should be removed andreplaced.NOTEBe sure points of ohmmeter probes are suf-ficiently long and sharp to penetrate any in-sulating varnish on diode terminals.(4) Replacing Diodes. Diodes of the rotating rec-tifier assembly which are found to be defective or inquestionable condition can be removed and replaced asfollows:(a) Unsolder wires from diodes.(b) Install new diode and attaching hardware.Tighten nut (40, figure 8-1) only finger tight.(c) Using a 25 to 40 watt soldering iron, solderleadwires to terminal of replaced diode. To protectdiode from damage due to heat caused by soldering,hold diode terminal with needle nose pliers as a heatsink and use a low melting point solder.(d) Allow each diode to cool after soldering.Tighten diode mounting nut (40) to torque of 30 inch-pounds.(e) Install end bell cover (7).(f) Tighten bolts (5).(5) Resistance.Use resistance check to locateopen circuits.b. Removal. Refer to paragraph 2-10 for generatorremoval.C h a n g e 68-1
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business