IMPORTANT SAFETY NOTICE WHEN SERVICING THIS CHASSIS, UNDER NO CIRCUMSTANCES SHOULD THE ORIGINAL DESIGN BE MODIFIED OR ALTERED WITHOUT PERMISSION FROM THE ZENITH RADIO CORPO RATION. ALL COMPONENTSSHOULD BE REPLACED ONLY WITH TYPES IDENTICAL TO THOSE IN THE ORIG INAL CIRCUIT. SPECIAL COMPO NENTS ARE USED TO PREVENT SHOCK AND FIRE HAZARD. THESE CRITICAL COMPONENTS ARE SHADED ON THE SCHEMATIC AND PARTS LIST FOR EASY IDENTIFICATION. THIS CIRCUIT DIAGRAM MAY OC CASIONALLY DIFFER FROM THE ACTUAL CIRCUIT USED. THIS WAY, IMPLEMENTATION OF THE LATEST SAFETY AND PERFORMANCE IM PROVEMENT CHANGES INTO THE SET IS NOT DELAYED UNTIL THE NEW SERVICE LITERATURE IS PRINTED. TEST POINTS SWITCHES A FM. ANTENNA INPUT D 1ST. FM. IF. INPUT F MPX. INPUT FM IF OUTPUT G H FM DETECTOR OUTPUT K AM IF INPUT L AM. RF INPUT M 19KHZ OSCILLATOR OUTPUT SW 1 SELECTION AM FM PHONO(1) PHONO(2) AUX MIC) SW 2 TAPE DUBBING (1-> 2 OFF 2->1) SW 3 TAPE MONITOR (1 SOURCE 2) SW4 MODE (STEREO MONO) - SW5 LOUDNESS (ON - OFF) SW6 FM MUTE (ON - OFFJ SW7 HIGH FILTER (ON-OFF) SW8 LOW FILTER (ON- off) 1W9 DE EMPHASIS ( 25us - 75us) SW10 SPEAKER (OFF A . B . A+B) SW 1 POWER (ON- OFF ) 1 SW3 TAPE MONITOR SWITCHES 1,5 PLAY BACK (1) RIGHT 2,6 SOURCE RIGHT 3,7 FLAY BACK(2) RIGHT 4,8 COMMON RIGHT 9,11 PLAY BACK(1) LEFT 10,14 SOURCE LEFT 11,15 PL AY BACK(2) LEFT 12,16 COMMON LEFT SW10 SPEAKER SWITCHES SW2 TAPE DUBBING SWITCHES 1,5 A— 8 RIGHT 2,6 OFF RIGHT 3,7 B—A RIGHT 4 ,8 COMMON RIGHT 9,13 A - B LEFT 10,14 OFF LEFT 11,15 B-A LEFT 12,16 COMMON LEFT 1,6 OFF RIGHT 2,7 A RIGHT 3,3 B RIGHT 4,9 A+B RIGHT 5,10 COMMON RIGHT 11,16 OFF LEFT 12,17 A LEFT 13,8 B LEFT 14,19 A+B LEFT 15,20 COMMON LEFT NOTf 1 SELECTOR SWITCH I AM 2 FM 3 PHONCXI) 4. PH0NCX2) 3. AUX 6. MIC 7. COMMON 2 ALL RESISTANCE VALUES IN OHMS KKILOHM M:MEGOHM,ALL RESISTORS 1/4W UNLESS OTHERWISE SPECIFIED 3 UNLESS OTHERWISE NOTED IN SCHEMATIC ALL CAPACITORS IN MFD PF PICOFARAD 4 THERE MIGHT BE SLIGHT CHANGES IN THE ACTUAL SET 3 ALL VOLTAGES ARE DC UNLESS OTHERWISE SPECIFIED, DC VOLTAGES SHOWN ARE MEASURED FROM CHASSIS WITH NO SIGNAL INPUT, LOUONESS SWITCH IN OFF POSITION. LINE VOLTAGE I20V AC, USING A HIGH IMPEDANCE DIGITAL MULTIMETER MODEL <strong>MC7051</strong> - SCHEMATIC 50
IC 101 PIN NO VOLTAGE 1 5.1 V 2 2.2 V 3 11.5 V 4 9.2 V 5 II.5V 6 3.6V 7 1.3V 8 2.8V 9 8.5V 10 0 V 11 12.2V 12 1.5V 13 0.7V 14 1.4V 15 0 V 16 1.0V IC 201 PIN NO VOLTAGE 1 2.0V 2 2.0V 3 2.0V 4 0 V 5 1.5V 6 5.6V 7 5.6V 8 5.6V 9 5.6V 10 5.6V 11 11.8V 12 3.7V 13 0 V 14 0 V 15 4.8V 16 0 V IC 301 PIN NO VOLTAGE 1 11.3 V 2 3.0V 3 5.1 V 4 8.2V 5 8.2 V 6 8.3V 7 0 V 8 0 V 9 2.3 V 10 1.5V 11 2.2V 12 2.2V 13 2.2 V 14 3.2V 51 MODEL <strong>MC7051</strong> - RF/IF/MPX CHASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE