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M 37-DC
GB
Adjustment Procedures
1. Tuner
Measuring instruments:
Standard/sweep signal generator, Frequency counter, Oscilloscope, DC voltmeter, AF voltmeter
Service works after replacing the front end: Alignment no. 6
The front end is a completely adjusted module. Only the IF filter is to be tuned to the IF amplifier.
Alignment
1. AM IF
MW, Sweep generator 450kHz (R
testpoint
<, ∆f = 10kHz
U
out
Oscilloscope to testpoint
DC voltmeter between testpoints
2. MW oscillator
MW
DC Voltmeter to testpoint
3. MW aerial
MW
bandpass circuit
Feed in a standard signal to testpoint
(MW RF)
U
<, m = 30%, f
out
AF Voltmeter to testpoint
4. LW oscillator
LW
DC Voltmeter to testpoint
5. LW aerial
LW
bandpass circuit
Feed in a standard signal to testpoint
(LW RF)
U
<, m = 30%, f
out
AF Voltmeter to testpoint
6. FM IF
FM, 98MHz
Sweep generator 98MHz to testpoint
Level abt. 100µV/40dBµV/75Ω,
Oscilloscope to testpoint
7. Stereo decoder
FM, 98MHz
Feed in a signal 98MHz to testpoint
no modulation, Level abt. 1mV/60dBµV/75Ω,
Frequency counter to testpoint
When replacing one of the ceramic
resonators, take care that the colour codes
of all resonators are the same.
IF (MHz)
IF Filter
IF Filter
Ident letter
10.6500
D
10.6750
B
10.7000
A
10.7250
C
10.7500
E
GRUNDIG Service
Preparation
= 50Ω) via 100nF to
out
C
7
1
6
= 1kHz
mod
7
6
= 1kHz
mod
7
4
3
A
1102
Colour
black
blue
1
B
2
red
5102
1103
orange
white
With 5111 and 5112 set alternating to maximum and
symmetry
and
With 5114 set to 0V
2
With 5123 set to 8.3V
Check at 531kHz for 1.0V
With 5102 set to Maximum at 558kHz
With 2106 set to Maximum at 1494kHz
B
Repeat this adjustment
With 5122 set to 8.3V
Check at 153kHz for 1.0
With 5103 set to Maximum at 198kHz
B
With F1 set to Maximum and Symmetry
A
With 3142 set to 152kHz
A
1
1110
6
5122
5123
C
9101
2106
5103
Abgleichvorschriften / Adjustment Procedures
Procedure
±
2mV
±
0.2V at 1602kHz
±
0.4V
±
0.2V at 279kHz
±
0.4V
±
1kHz
F1
1124
4
1
6
8
4
3
7
5115
9116
3142
2140
1
2
5114
5111
5112
1121
1
3 - 3
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