Zenith MC7031 - MC7031 Schematic

TEST POINTS
A;
FM.ANTENNA INTUT
D;
1ST FMIF INPUT
G;
2ND FMIFOUTPUT
H;
FM DETECTOR OUTPUT
L;
AM.RF. & IF. INPUT
M;
l»KHZ GAIN
K;
AM IF WPUT
VR CONTROL
R404
VOLUME
R406
BALANCE
R4I4
BASS
R4I7
TREBLE
SWITCHES
S 501
POWER (ON-OFF)
SI FUNCTION SELECTOR
(AM FM. PHONO AUX)
S2 AFC (ON-OFF)
S3 MUTING (ON-OFF)
S4
LOUDNESS (ON-OFF)
S5
MODE (MONO-STEREO)
S6
HIGH FILTER (ON-OFF)
S7
LOW FILTER (ON- OFF)
S8
MONITOR (TAPE-SOURCE)
S9
SPEAKER (OFF-A.B A B)
SIO
DE - EMPHASIS ( 75US - 25US )
AF BOARD TRANSISTORS
NO DE3CRPTI0N
01401,1491
DFF AMP
01402 ,1492
CURRENT SOURCE
01403,1493
BIAS
01404,1494
01FF AMP
01406, 1499
PRE DRIVER
QI406, 1456
BIAS
01407, 1457
PROTECTOR
0I4O8, 1458
PROTECTOR
01409,1499 DRIVER
01410, l4«o
DRIVER
01-411, 1461
OUTPUT
01412, 1462
OUTPUT
NOTE
1 ALL RESISTANCE VALUES IN OHM K:KILOHM , M:MEGOHM
THE WATTAGE OF RESISTORS NOT SPECIFICALLY DESIGNATED
IS 1/4 WATT
2 UNLESS OTHERWISE NOTED IN SCHEMATIC ALL CAPACITORS IN MF
PF- PICOFARAD
3. THERE MIGHT BE SLIGHT CHANGES IN THE ACTUAL SET
4. ALL VOLTAGES ARE DC UNLESS OTHERWISE SPECIFIED
O.C. VOLTAGES SHOWN ARE MEASURED FROM CHASSIS, WITH
NO SIGNAL INPUT, LOUDNESS SWITCH IN "OFF" POSITION, LINE
VOLTAGE 120V . AC USING A HIGH IMPIDANCE DIGITAL MULTIMETER.
IC VOLTAGES
IC 301
PIN MONAURAL
STEREO
1
11.45
12
2 3.2 3.1
3
5.5
5.2
4
9.0
9.3
5
9.0
.3
6
13.7
0.7
7
0
0
8
0.04 .4
9 2.4
2.37
10
1.58 1.56
II
2.2
2.4
12
2.4
2.4
13 2.4 2.4
14 3.3
3.2
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.
NOTE - SEE PARTS LIST FOR
PRODUCTION CHANGES
SWITCH:
POSITIONS
CONNECTIONS
1. AM.(SHOWN)
5- 1
2 FM 5-2
3. PHONO
5-3
4.AUX.
5-4
ARROW INDICATES MOVEMENT OF WIPER CORRESPONDING
TO CLOCKWISE ROTATION OF SHAFT.
SWITCH CONTACTS HAVE BEEN ASSIGNED ALPHANUMERIC
DESIGNATIONS TO ASSIST SERVICE TECHNICIANS IN
CIRCUIT TRACING.
MODEL MC7031 - SCHEMATIC
44