Superseder II

4.2 FINDING A SHORTED DISCHARGE TRANSISTOR.since all diacha.rge transistors ere vired in pararsinglelel, ashorted transistor rilr short the entire Lanx.necessaryIt isthen, to test each trensistor individuatry intoorderfind the defecLive one.The procedure that foltows will allow the findingshortedof thetransistor wiLhout reguiring removal and test ingeach deviceofindividually.4.2.1 EQUIPT{E}II REOUIRED. (see fig 4>1) Voltmeter (digital prefered).2) Battery, Z4V.3) Lamp, 24V (lanp must draw at least .S A).4.2.2 PROCEDUFIE.1) TURN UNIT OFF,. DISCONNECT IT FROM TI{E WALL OUTLET.2, connect the ranp in place of the discharge currentIimiLer (see fig 4).3) Connect the unit to the battery.4) If the lamp illuminates, it indicates that there is ashort in the discharge circuit, generated by one ormore shorted transistors.5) l{easure the voltage across the individual .zz oHMemitter resistors.A non zero reading, approximately .lV for a lampdrawing .5A, indicates currenL frow due to a transisterwith a collector to emitLer short.NorE: A rrcn zero reading on arI emitter resistors-approximately .02V for a lamp drawing . SA_indicates a different failure uode ( correctorto base short; refer to step ?>.6) -Removeany shorLed transistors ana repeat steps 4 and5 untir a no short reading is obtained.tiveReptacldevicesdefec-only with types HJlso23, MJlsb04, uJ15o02or 2N6031.7, If all transistors appear to be shorted (ALLresistorsemitterreading a vortage), Lhen, one or Dore havefailed rith a collector to base short, causing theremainder of the transistors to turn on. It witr thenbe necessary to check each transistor individually.This cen be greatry faciritated by searching io. azero reading. TIeis will indicate the shorted device.8) when repracing transistors, add heat sinking compoundand nake sure that the base and emitter pin"properry ln the socket contacts. Torque the "rrg"g" screwsproperly to insure a good thermal transfer.NorE: If repracing any of the contror Lransistors (e1and Q2), note that they are Dounted with a micainsulator.Superseder II - Technieal Manual, r€lv O - page Zs