United-Motors-Service-Delco-989127 电路原理图.pdf

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1、VOLUME R-18, MOST-OFTEN-NEEDED 1958 RADIO SERVICING INFORMATION OLDSMOBILE MODEL 989127 (Continued on page 53) TROUBLE SHOOTING THE OUTPUT STAGE A quick way to determine that the 2N278 is conducting can be made by checking the collector voltage, from tran sistor case to the radio case. If no voltage

2、 is present, the transistor is not conducting or the transistor heat radiator is grounded to the radio case. If the voltage at the collector is higher than listed, the transistor is conducting too heavily (check with mi I ham meter) or the output trans former is open The amount of current the transi

3、stor conducts is determined hy the voltages at each element, the resistor in the base and emitter circuits, the input trans former secondary resistance, and the transistor itself. The most common defect in the transistor is an internal short between emitter and collector To check for this, use the f

4、ollowing procedure 1. Unsolder base and emitter leads from the circuit. 2. Set ohmmeter on the R x 1” scale (no other scale should be used.) 3. Place negative lead of ohmmeter (polarity refers to internal ohmmeter battery) on collector and positive lead on the emitter. 4. The transistor is shorted i

5、f reading is 0 PRINTED CIRCUIT SHOWN IN HEAVY LINES, I2BL6 I2AD6 R F AMR OSC-MOO. I2AF6 I.F.AMP. /T I2F8 DEI- lI AUDIO UlOHW -O -3J CD S m2rn . O O JO _ airr VOLTAGE MEASURED TERMINAL TO CHASSIS WITH A VTVM-NO SIGNAL AND 12 O VOLTS AT I ULUS 31 OSCILLATOR GRID VOLTAGE TAKEN WITH SET TUNED TO IOOOKC.

6、 TOTAL A DRAIN AT 12 V -2 3 AMPS , TOLERANCE ON VOLTAGES IO% O - COLORS OF TERMINALS ON SERVICE PARTS * -INDICATES LEAD FROM TUNER COIL ASSY 52 收音机爱 好者资料库 RadioFans.CN c MOST-OFTEN-NEEDED 1958 RADIO SERVICING INFORMATION Cljtzi S7 fKl W rnr uuWuu PARTS LAYOUTTUBE VIEW /ee/ PARTS LAYOUTTOP VIEW - AUD

7、IO POWER SUPPLY UNIT ALIGNMENT PROCEDURE Output Meter Connections Across Voice Coil w Generator Return.To Receiver Chasis Dummy Ant nna.In Series With Generator Volume Control Position.Maximum Volume Tone Control Position.Treble Position Generator Output.Minimum for Readable Indication CONNECT VACUU

8、M TUBE VOLTMETER ACROSS SPEAK ER VOICE COIL DURING ALIGNMENT. Series Capacitor or Dummy Antenna Connect Signal Generator to Signal Generator Frequency Tune Receiver to Adjust in Sequence For Max. Output 0.1 Mfd. 12AD6 Grid (Pin #7) 262 KC High Frequency Stop A, B. C, D 0.000068 Mfd. Antenna Connecto

9、r 1615 KC High Frequency Stop *E, F. G 0.000068 Mfd Antenna Connector 600 KC Signal Generator Signal J. K 0.000068 Mfd Antenna Connector 1615 KC High Frequency Stop F. G 0.000068 Mfd Antenna Connector 1100 KC Signal Generator Signal L* Before making this adjustment check mechanical setting of oscill

10、ator core H. The rear of the core should be 1% from the mounting end of the coil form. (This measurement is readily made by inserting a suitable plug in the mounting end of the coil form.) Core adjustment should be made with a non-metallic screw driver. *L is the pointer adjustment which is on the c

11、onnecting link, between the pointer assembly and core guide bar (See tuner Dwg.). It should be adjusted so that when looking directly at the dial the pointer is on the 1100 KC mark. This setting is to give the correct relationship between the pointer and the dial when the radio is installed in a car. With the radio installed and the car antenna plugged in adjust the antenna trimmer G” for maximum volume with the radio tuned to a weak station between 600 and 1000 KC (see sticker on case.) 53 收音机爱 好者资料库 RadioFans.CN