Galvin-Mfg-Co（Motorola）-94M1 电路原理图.pdf

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1、收音机爱 好者资料库 RadioFans.CN VOLUME R-20, MOST-OFTEN-NEEDED 1960 RADIO SERVICING INFORMATION MOTOROLA MODEL 94M1 (Continued from page 81) SERVICING PRECAUTION - When servicing this re ceiver, probing with a screwdriver (checking for spark to ground from various points) must be avoided, because the plate

2、power is obtained directly from the storage battery and high currents can flow through the components causing permanent damage. The transistor stage is especially sus ceptible to damage from this type of check. If the tran sistor BASE electrode is shorted to ground (either directly or through any ot

3、her path) the BASE bias willbe removed allowing excessive current to flow through the transistor causing permanent damage by melting the indium junctions in the transistor. TUBE CHECK - Substituting a known good tube for a suspected one is the best and only check recommended at this time. CIRCUIT SI

4、GNAL TRACING - Defective stages can be located by injecting a signal from stage to stage. A signal generator with a 400 cycle output can be used for this pur pose as it has asource of RF and audio signals for checking the respective stages. In the transistor stages, the signal is injected between th

5、e base electrode and chassis; in tube stages, the signal is injected between the input grid and chassis. The signal is injected from stage to stage until the defective stage is located, and then the defective com ponent is located bv resistance and voltage measurements. This system of servicing will

6、 locate defects in stages caused by faults in the signal paths where the defect does not show up as a voltage reading difference. CAUTION: When using asignal generator as a signal source a .5 mf 100V capacitor must be used in series with the ground lead to prevent damage to transistors. ALIGNMENT Th

7、e following alignment procedure should be performed with receiver covers in place. Connect an output meter across the speaker voice coil, set volume to maximum, Attenuate signal generator output to maintain 1. 79 volts on output meter at all times to prevent overloading the receiver. Refer to alignm

8、ent detail for adjustment locations. I GENERATOR CONNECTION GENERATOR FREQUENCY (400 cycle mod) TUNER SET TO I ADJUST IF ALIGNMENT 1. I Ant recept thru I . 1 mf Do not perform steps 3,4, 5 step 5 should be last adjustment. I ANTENNA TRIMMER 7, I _ - Weak station 7 With radio installed in car and I a

9、round 1400 Kc antenna fully extended, adjust I antenna trimmer for maximum, NOTE; The cores of the IF transformers are adjusted from the top of the can by using a hex alignment tool such as shown in detail. This is accomplished by first adjusting the top core and then dropping the tool down until it

10、 makes contact with the bottom core. p, Lif to fit RFCF.VFR ANT CORE RKORE OSC TRIM Q TOPCORE. r rSK 1200 KC 1200 KC 1610 KC r-T 1ST IF 262.5 KC TO RECEIVER -ANTENNA RECEPTACLE I METAL SHIELD CAN I MUST BE ATTACHEO TO PLUG DUMMY ANTENNA DETAIL HEX ALIGNMENT - TOOL C 0 o o o I o g O G/G-V/G (. r GO J V O BOTTOM_iL CONE 1 I .W; STOP C0REx BOT CORE- IF ALIGNMENT DETAIL ALIGNMENT POINT LOCATION DETAIL 82 收音机爱 好者资料库 RadioFans.CN