General-Electric-Co-P746A 电路原理图.pdf

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1、VOLUME R-18, MOST-OFTEN-NEEDED 1958 RADIO SERVICING INFORMATION GENERAL ELECTRIC Models P745A, P746A TO REMOVE CIRCUIT BOARD 1. Remove cabinet back by twisting a coin in the two slots provided aloag bottom of the cabinet. 2. Remove the four screws that secure the circuit board to cabinet bosses. ( S

2、EE COMPONENT WIRING DIAGRAM FOR MOUNTING SCREW POSITIONS). 3. Remove the two screws that secure circuit board to speaker. ( SEE COMPONENT WIRING DIAGRAM FOR MOUNTING SCREW POSITIONS). 4. Swing circuit board out of cabinet front. Leave all connecting leads attached to volume control and tunin0 capaci

3、tor. TO REMOVE TUNING CAPACITOR 1. Follow steps 1 and 2 as above. 2. Remove tuning knob by unscrewing the thumbscrew in its center in a counterclockwise direction. 3. Remove the flat head screws located under tuning knob. TO REMOVE VOLUME CONTROL 1. Follow steps 1 through 3 as above. 2. Remove on-of

4、f volume knob by unscrewing the screw in the center of the knob. 3. Remove hex nut from volume control shaft. 4. Move tuning capacitor slightly and lift out volume control. TROUBLESHOOTING A check of the battery condition and total current drain of the receiver should be made first. All current meas

5、urements are made at quiescence with the receiver turned on, volume control at maximum, tuning gang closed, and with no signal conditions. CAPACITORS is 15 to 20 milliammeter The total receiver current drain mils. This is measured by inserting i in series with the batteries. If an excessive total cu

6、rrent drain is recorded, the individual collector current readings of each transistor should be checked. An excessive current reading may mean a shorted transistor; no current will indicate that a transistor or associated ciicuit components are defective. A single-edge razor blade is a satisfactory

7、tool for cutting the copper circuit wiring, so that a milliammeter can be inserted in series with the break to measure the current flow. After each current check is completed, solder the cut carefully to complete the circuit again. NO RECEPTION: 1. Check battery voltage and battery contacts. 2. Chec

8、k on-off switch. 3. Check all antenna lead connections, 4. Check coil L2. WEAK AUDIO: 1. Check battery voltage for 4.5 volts. 2. Check battery current. 3. Check transistor collector currents. 4. Check alignment. CIRCUIT board MOUNTING SCRE RS-1378 CA,B,C,D Tuning Capacitor. RS-1022 Cl, 3 .Olmf., 450

9、V.-. C2, 7 .Olmf., 50V. C4 150mmf., 300V. RS-14G2 C5 8mf., 6 V. . . C6, 9 390mmf., 300V. RS-1024 CIO,17,19 .05mf., 50V. C18 003mf., 100V RS1463 C16 32mf., 6V. RS-1460 Cll,12,14,15 3mf., 6V. . CIRCUIT BOARD MOUNTING SCREW 73 收音机爱 好者资料库 RadioFans.CN VOLUME R-20, MOST-OFTEN-NEEDED 1960 RADIO SERVICING

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