Ford-Motor-Car-Co-FEG-18806H 电路原理图.pdf

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1、VOLUME R-17. MOST-OFTEN-NEEDED 1957 RADIO SERVICING INFORMATION MOTOROLA MOTOROLA 75MF FORD FEG-18806-H e (For alignment see the illl next page adjacent at right) -Hi- i I WU 18 I XI Plef E|m 0i8 * n EfHi- “lilww TU_ X% 218 ! 17*03 TOA NO VMS 1J0-N0 SERVICE NOTES RADIO POLARITY - WHEN SERVICING THIS

2、 RECEIV ER ON THE SERVICE BENCH, BE SURE THAT THE RE CEIVER A LEAD IS CONNECTED TO THE POSITIVE SIDE OF THE POWER SOURCE AND THAT THE RECEIV ER HOUSING IS CONNECTED TO THE NEGATIVE SIDE. IF CONNECTED OTHERWISE, THE RECEIVER WILL NOT OPERATE AND DAMAGE TO COMPONENTS MAY RESULT. TRANSISTOR REPLACEMENT

3、 - When replacing a tran- sistor, be sure that the transistor mounting screws are se curely tightened* If not securely tightened, the transistor may be damaged from lack of proper heat dissipation. NOTE: When a transistor is replaced, the emitter cur rent should be checked (see EMITTER CURRENT ADJUS

4、T MENTS). EMITTER CURRENT ADJUSTMENT - The emitter cur rent is adjusted by variable resistor R-Z3 for 390 Ma flow through the transistor with IZ volts at the receivers A” lead. The current is adjusted by measuring the voltage drop across the top section of T-4 primary winding. Con nect the negative

5、lead of a low range VTVM to the yellow lead of T-4 (top of primary winding) and the positive VTVM lead to the white lead (tap on primary) of T-4; adjust R-Z3 .for a. 8Z volt reading (see ALIGNMENT LOCATIONS photo), TO SIGNAL * GENERATOR / MMF | PLUG TO FIT RECVrJ ANT RECEPT To RECEIVER_J ANT RECEPT

6、DUMMY ANTENNA DATA CORE ALIGNMENT TOOL DETAIL i m ? * c (.J 6. TRANSISTOR CHECK - The transistors used in this re ceiver can be expected to give unusually long trouble-free life. However, the following transistor checks are provided to facilitate servicing; Substituting aknown good transistor for a

7、suspected one is the simplest and most positive way of checking tran sistors. The transistor may be checked for shorts and opens by using an ohmmeter. This check primarily measures the ability of a transistor to conduct current in one direction and to resist current flow in the opposite direction. T

8、he resistance in the conduction direction is very low in rela tion. to the resistance in the non-conduction direction. This check is made by connecting the ohmmeter leads as shown in illustration. SOLLECTOR EMITTEKV / BASE TRANSISTOR CONNECTIONS (PIN VIEW) 68 收音机爱 好者资料库 RadioFans.CN VOLUME R-l , MOS

9、T-OFTEN-NEEDED 1957 RADIO SERVICING INFORMATION MOTOROLA 75MF, FORD FEG-18806-H, Alignment Information (Continued) Connect an output meter across the speaker voice coil. Set tone control to high and volume control to maximum. Atten uate signal generator output to maintain 1.79 volts (1 watt) on outp

10、ut meter to prevent overloading. Input voltage should be 14. 4 volts. GENERATOR CONNECTION TUNER SET TO ADJUST .e mo IF ALIGNMENT 1. I 12AD6 grid (pi I 7) thru . 1 mf I I chassis Adjust for maximum, RF ALIGNMENT I I 2. I Antenna recept I 1610 Kc I Hi end stop I 5, 6 Do not perform steps 3, 4, 5 last

11、 adjustment should be step 5, SENSITIVITY CONTROLj | | 7. I Antenna recept | thru dummy ANTENNA TRIMMER Adjust for maximum, 600 Kc at 5 microvolts Sensitivity control Adjust for 1. 79 volts output. Weak station around 1400 Kc Adjust for maximum with radio installed in car and antenna fully extended. TO CALIBRATE POINTER Tune radio to lOOOKc signal and rotate pointer adjusting cam until center of pointer coincides with the center of the 1000 Kc mark on dial scale. - rr (Circuit diagram is on the preceding page at left.) 69 ALIGNMENT ADJUSTMENT LOCATIONS 收音机爱 好者资料库 RadioFans.CN