Zenith MC7041 - Alignment for MC7051 Model

RF, IF AND MPX ALIGNMENT PROCEDURE
FOR MODEL MC7051
STEP
CONNECT
GENERATOR
TO
DUMMY
ANTENNA
CONNECT
VTVM/
SCOPE TO
INPUT
SIGNAL
FREQ.
SET DIAL
TO
ADJUST
PURPOSE
VOLTAGE REGULATOR ADJUSTMENT
CAUTION: Regulator Must Be Adjusted For Correct B+ Voltage.
1
- -
VTVM
Pin 505
-
-
R509
Adjust For +33V.
AUDIO OUTPUT IDLE CURRENT ADJUSTMENT
CAUTION : Output Stages Must Be Adjusted For Proper Idle Current Under No Signal
Conditions Before Performing Other Adjustments Or Alignment.
2
VTVM
Across
R1418
No Signal
Input
R1409
Adjust Controls for 8 m V Across
Corresponding Resistors. This
Would Equal Approximately
16 mA.
3
Across
R1468
No Signal
Input
R1459
Adjust Controls for 8 m V Across
Corresponding Resistors. This
Would Equal Approximately
16 mA.
AM ALIGNMENT - PREFERRED METHOD - WITH AM SWEEP GENERATOR
NOTE: For AM IF Alignment Use AM Sweep Signal Generator Of 10 KHz Deviation, 60 Hz Modulation For Full Bandpass Display. Bandswitch
In AM. Also Connect Modulation Frequency To Scope Horizontal. (If AM Sweep Not Available, See Steps 17 Through 31.)
4 Short C1J (AM Gang Antenna Section) To Chassis Ground.
5 Test Point "K"
AM I F Input
Generator
Output
Probe "A"
Scope
Detector
Output
Across R1 10
+ 455 KHz
Gang
Closed
-
Adjust Generator To Center
Frequency Of Ceramic Filter.
6
Test Point "K"
AM I F Input
Generator
Output
Probe "A"
Scope
Detector
Output
Across R1 10
Tune Generator To Center Total Bandpass
Waveform. Do Not Change Generator Frequency
For Remainder Of AM IF Alignment.
Adjust Generator To Center
Frequency Of Ceramic Filter.
7
Test Point "K"
AM I F Input
Generator
Output
Probe "A"
Scope
Detector
Output
Across R1 10
Center Freq.
Of Ceramic
Filter In T102
Gang
Closed
L103, L104
(T102)
Adjust For Maximum Gain And
Symmetry.
8
Test Point "K"
AM I F Input
Generator
Output
Probe "A"
Scope
Detector
Output
Across R1 10
Center Freq.
Of Ceramic
Filter In T102
Gang
Closed
T101
Adjust For Maximum.
9
Remove Short Between C1J And Chassis Ground.
10 One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None Scope
1400KHz
1400KHz
C1 K
Set Oscillator To Dial Scale.
1 1
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
600KHz
600KHz
L102
Set Oscillator To Dial Scale.
12
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
Repeat Steps 1 0 & 11 For Minimum Change.
Set Oscillator To Dial Scale.
13
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
1400KHz 1400KHz C1J
Align Antenna Stage.
14
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
600KHz
600KHz
L101 If
Necessary
Align Antenna Stage.
15
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
Repeat Steps 13 & 14 For Minimum Change.
Align Antenna Stage.
16
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R 1 1 0
1000 KHz
1000 KHz
R106
Adjust For A Reading Of 4 To 5
On Meter M102 With Input Of
74dBV(5mV).
AM ALIGNMENT - ALTERNATE METHOD - IF AM SWEEP GENERATOR IS NOT AVAILABLE
NOTE: For AM IF Alignment Use A Signal With 400 Hertz Modulation. Bandswitch In AM.
17 Short C1J (AM Gang Antenna Section) To Chassis Ground.
18
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
+ 455 KHz
Gang
Closed
—
19
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
Rock Generator While Adjusting L103
(T102 Primary) For Maximum.
Adjust For Maximum.
20
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
Rock Generator While Adjusting L104
(T102 Secondary) For Maximum.
Adjust For Maximum.
21
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
Repeat Steps 19 & 20 For Minimum Change.
Adjust For Maximum.
22
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
Equal Output Should Be Found If Generator
Is Detuned Equal Frequency Each Side
Maximum.
Adjust For Maximum.
23
Test Point "K"
AM IF Input
Generator
Output
Probe "A"
VTVM
Detector
Output
Across R 1 1 0
Center Freq.
Of Ceramic
Filter In T102
Gang
Closed
T101
Adjust For Maximum.
24 Remove Short Between C1J And Chassis Ground.
25
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
VTVM
1400 KHz
1400 KHz
C1K
Set Oscillator To Dial Scale.
26
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
600 KHz
600 KHz L102
Set Oscillator To Dial Scale.
27
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
Repeat Steps 26 & 27 For Minimum Change.
Set Oscillator To Dial Scale.
28
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
1400 KHz
1400 KHz
C1J
Align Antenna Stage.
29
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
600 KHz
600 KHz
L101 If
Necessary
Align Antenna Stage.
30
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
Repeat Steps 29 & 30 For Minimum Change.
Align Antenna Stage.
31
One Turn Loosely
Coupled To AM
Wavemagnet
Antenna
None
Detector
Output
Across R110
1000 KHz
1000 KHz
R106
Adjust For A Reading Of 4 To 5
On Meter M102 With Input Of
74dBV(5mV).
14