RF,
IF, MPX AND AUDIO ALIGNMENT PROCEDURE
FOR MODELS
MC7031,
MC7041 - Cont'd.
STEP
CONNECT
GENERATOR
TO
DUMMY
ANTENNA
CONNECT
VTVM/
SCOPE TO
INPUT
SIGNAL
FREQ.
SET DIAL
TO
ADJUST
PURPOSE
36
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
+ 98 MHz
98 MHz
R211
(Mute)
Adjust For No Sound Output
When Input Is Below
1.7/xV
With Mute Switch ON.
37
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
+ 98 MHz
98 MHz
R208
(Meter)
Adjust For A Reading Of 6 On
Meter M102 With 60 dbV (1mV)
Input.
NOTE:
For FM Detector Alignment Use A Signal Of 75 KHz Deviation, 1 KHz Modulation. Also Connect Generator Modulation Frequency To
Scope Horizontal. Adjust Generator IF Frequency To Center Total Bandpass Waveform. Do Not Change Generator IF Frequency For
Remainder Of IF Alignment. (If Your Generator Does Not Provide Output For Audio Modulation Frequency Use Horizontal Output
From Generator, Or Scope Horizontal Sweep, And Follow Step 38C.) Minimum Distortion Can Only Be Achieved By Use Of Step 38A
Below.
38
Test Point "D"
FM IF Input
At Q2 Base
Generator
Output
Probe "A"
A. Distortion
Analyzer
(Thru a 100
Usee De-
emphasis
Network
Probe "B"
And Scope.
B. Scope
C. Scope
Center
Frequency
Of Ceramic
Filters Y201,
Y202,
Y203.
Gang
Closed
L205,
L206
(T202)
A. Preferred Method: Distortion
Analyzer At Test Point "H"
Should Read Minimum Distortion.
B. Alternate Method: Adjust For
Linear Scope Trace - No Curve At
Ends Of Trace. Disregard Meter
Reading.
C. Alternate Method: Adjust For
Maximum Length And Symmetry,
Similar To Scope Pattern "B".
39
Test Point "D"
FM IF Input
At Q2 Base
Generator
Output
Probe "A"
Test Point
"H"
Center
Frequency
Of Ceramic
Filters Y201,
Y202,
Y203.
Gang
Closed
L205
(T202)
Adjust For Center Reading On
Tuning Meter M101.
40 Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
106 MHz
106 MHz C1E Set Oscillator To Dial Scale.
41
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
90 MHz
90 MHz L4
Set Oscillator To Dial Scale.
42
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
Repeat Steps 40 & 41 For Minimum Change.
Set Oscillator To Dial Scale.
43
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
106 MHz 106 MHz C1C
Align FM Detector Stage For
Maximum.
44
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
90 MHz 90 MHz L2 If Necessary
Align FM Detector Stage For
Maximum.
45
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
106 MHz
106 MHz
C1
A
Align FM Antenna Stage For
Maximum.
46
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
90 MHz
90 MHz
L1
Align FM Antenna Stage For
Maximum.
47
Test Point "A"
FM Antenna Post
(Disconnect Antenna)
300 Ohm
Repeat Steps 43 Thru 46 For Minimum Change.
Align FM Antenna Stage For
Maximum.
NOTE:
Apply Sufficient Signal Level — Approx. 100 Microvolts — To Obtain Full Limiting At Point Near 98 MHz.
48
Frequency
Counter And/
or Scope
Test Point
"M"
Unmodulated
R F Carrier
R303
(VCO)
A. Frequency Counter Should Read
19 KHz, +100 Hz.
B. Alternate Method: Connect Test
Point "M" Signal To Scope Vertical
And An Accurate 19 KHz Signal To
Scope Horizontal Input. Adjust For
One Square Synchronized Waveform.
49
Scope And/Or
AC VTVM
Left Tape
Output
98 MHz
10%
Pilot
(L + R) (L - R)
(L Only)
R313
Adjust For Separation. Maximum
Left Output.
50
Right Tape
Output.
98 MHz
10%
Pilot
(L + R) (L - R)
(L Only)
Check For Separation. Minimum
Right Output.
NOTE:
Do Not Readjust Control R303 After Step 48.
CERAMIC FILTERS
COLOR
CODE
NOMINAL CENTER
FREQUENCY
FREQUENCY
RANGE
Black
10.64 MHz 10.61 to 10.67 MHz
Blue
10.67 MHz
10.64 to 10.70 MHz
Red
10.70 MHz
10.67 to 10.73 MHz
Orange
10.73 MHz
10.70 to 10.76 MHz
White
10.76 MHz
10.73 to 10.79 MHz
13
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