Grundig RR 720 CD Serviceanleitung Seite 14

Abgleichvorschriften / Adjustment Procedures
3. Tuner
Measuring instruments: Signal generator, sweep generator, oscilloscope, digital voltmeter.
Function switch: Radio
Adjustment
1. AM IF Couple in a sweep signal of 450kHz to L503 (ferrite aerial)
via a loop aerial.
Oscilloscope to testpoint
Band switch: MW
2. MW Oscillator MW f
u
Couple in a standard signal to L503 (ferrite aerial) via a
loop aerial, (f
that the signal is just visible).
Digital voltmeter to testpoint
Band switch: MW
3. MW Aerial MW 612kHz, MW 1404kHz
bandpass Couple in a standard signal to L503 (ferrite aerial) via a
loop aerial, (f
that the signal is just visible).
Oscilloscope to the headphone socket.
Band switch: MW
4. LW Oscillator LW f 146kHz, f
u
Couple in a standard signal to L504 (ferrite aerial) via a
loop aerial, (f
that the signal is just visible).
Digital voltmeter to testpoint
Band switch: LW
5. LW Aerial LW 164kHz, LW 272kHz
bandpass Couple in a standard signal to L504 (ferrite aerial) via a
loop aerial, (f
that the signal is just visible).
Oscilloscope to the headphone socket.
Band switch: LW
6. FM IF FM 10.7MHz
Couple in a sweep signal via a 10nF capacitor to testpoint
TP 1
Oscilloscope to testpoint
Band switch: FM
7. FM Oscillator FM f 87.5MHz, f
u
Couple in a standard signal via a 10nF capacitor to
testpoint
U as low as possible so that the signal is just visible).
a
Digital voltmeter to testpoint
Band switch: FM
8. FM Aerial FM 90MHz, FM 106MHz
bandpass Couple in a standard signal via a 10nF capacitor to
testpoint
U as low as possible so that the signal is just visible).
a
Oscilloscope to the headphone socket.
Band switch: FM
2 - 5
Preparations
(IC502 Pin 18).
TP 5
522kHz, f 1620kHz
o
= 1kHz, m = 30%, U as low as possible so
a
mod
TP 6
= 1kHz, m = 30%, U as low as possible so
a
mod
281kHz
o
= 1kHz, m = 30%, U as low as possible so
a
mod
TP 6
= 1kHz, m = 30%, U as low as possible so
mod a
/ (GND).
TP 2
(IC502 Pin 19).
TP 4
108MHz
o
= 1kHz, ∆f = 22.5kHz,
/ (GND) (f
TP 1 TP 2
mod
TP 7
= 1kHz, ∆f = 22.5kHz,
/ (GND) (f
TP 1 TP 2
mod
TP 6
TP 7
Adjust to maximum with T502.
At f (1620kHz) adjust to 8.2V
o
(CN501 Pin 9).
At 612kHz adjust to maximum with L503 (MW aerial coil,
move).
At 1404kHz adjust to maximum with TC502.
Repeat this adjustment alternately.
At f (281kHz) adjust to 7.9V
o
(CN501 Pin 9).
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 f (108MHz) adjust to 7.9V
o
(CN501 Pin 8).
At 90MHz adjust to maximum with L501 (bend).
At 106MHz adjust to maximum with TC501.
Repeat this adjustment alternately.
Tuner Board
TP 1
TP 2
RR 720 CD / RR 760 CD
Adjustment Process
±
0.1V with L505.
±
0.1V with L506.
S-Kurve
S Curve
±
0.1V with L502 (bend).
TP 3
TP 5
TP 4
GRUNDIG Service