GRUNDIG Service
2 - 5
Abgleichvorschriften / Adjustment Procedures
RR 740 CD / RR 770 CD
3. Tuner
Measuring instruments:
Signal generator, Sweep generator, Oscilloscope, Digital voltmeter.
Function switch: Radio
Adjustment
Preparations
Adjustment Process
Adjust to
maximum
with
T502.
At
1620kHz
adjust to
8.2V
±
0.1V
with
L505
.
At
612kHz
adjust to
maximum
with
L503
(MW aerial coil,
move).
At
1404kHz
adjust to
maximum
with
TC502
.
Repeat this adjustment alternately.
At
281kHz
adjust to
7.9V
±
0.1V
with
L506
.
At
164kHz
adjust to
maximum
with
L504
(LW aerial coil,
move).
At
272kHz
adjust to
maximum
with
TC503
.
Repeat this adjustment alternately.
Adjust to
maximum and symmetrical
response
with
T501
.
Adjust to
symmetrical response
centered
with
T503
.
Repeat this adjustment alternately.
At
108MHz
adjust to
7.9V
±
0.1V
with
L502
(bend).
At
90MHz
adjust to
maximum
with
L501
(bend).
At
106MHz
adjust to
maximum
with
TC501
.
Repeat this adjustment alternately.
Couple in a
sweep signal
of 450kHz to
L503
(ferrite aerial)
via a loop aerial.
Oscilloscope
to
testpoint
TP 5
(IC502 Pin 18).
Band switch: MW
MW, 1620kHz
Digital voltmeter
to
testpoint
TP 6
(CN501 Pin 9).
Band switch: MW
MW 612kHz, MW 1404kHz
Couple in a
standard signal
to
L503
(ferrite aerial) via a
loop aerial, (f
mod
= 1kHz, m = 30%, U
a
as low as possible so
that the signal is just visible).
Oscilloscope
to the
headphone socket
.
Band switch: MW
LW, 281kHz
Digital voltmeter
to
testpoint
TP 6
(CN501 Pin 9).
Band switch: LW
LW 164kHz, LW 272kHz
Couple in a
standard signal
to
L504
(ferrite aerial) via a
loop aerial, (f
mod
= 1kHz, m = 30%, U
a
as low as possible so
that the signal is just visible).
Oscilloscope
to the
headphone socket
.
Band switch: LW
FM 10.7MHz
Couple in a
sweep signal
via a 10nF capacitor
to testpoint
TP 1
/
TP 2
(GND).
Oscilloscope
to
testpoint
TP 4
(IC502 Pin 19).
Band switch: FM
FM, 108MHz
Digital voltmeter
to
testpoint
TP 7
(CN501 Pin 8).
Band switch: FM
FM 90MHz, FM 106MHz
Couple in a
standard signal
via a 10nF capacitor
to
testpoint
TP 1
/
TP 2
(GND) (f
mod
= 1kHz,
∆
f = 22.5kHz,
U
a
as low as possible so that the signal is just visible).
Oscilloscope
to the
headphone socket
.
Band switch: FM
1. AM IF
2. MW Oscillator
3. MW Aerial
bandpass
4. LW Oscillator
5. LW Aerial
bandpass
6. FM IF
7. FM Oscillator
8. FM Aerial
bandpass
S-Kurve
S Curve
TP 1
TP 2
TP 3
TP 5
TP 4
TP 6
9
8
TP 7
Tuner Board
