Sony LBT-A57CD - FM Section

SECTION 2
ELECTRICAL ADJUSTMENTS
Precautions in Repairing
If the front end unit fails, it is difficult to repair the inner
circuits, so replace the entire front end unit.
FM SECTION
FM Discriminator Adjustment (NULL Adjustment)
Setting :
BAND switch: FM
FM RF stereo signal
generator
750 coaxial
set
Carrier frequency: 98MHz
Modulation:
Except G, IT: aes pot deviation FM ANTENNA terminal
G, IT: 1kHz, 40kHz deviation (53%)
Output level: 1mV (60dBy.) vom
(DC range)
TP1
NULL terminal
Procedure :
1, Tune the set to 98MHz.
2. Adjust T21 for 0V reading on the VOM.
Note: FM Tuning Level adjustment should be made after
FM discriminator alignment.
FM Tuning Level Adjustment
Setting :
BAND switch: FM
FM RF stereo signal
generator
750 coaxial
set
Carrier frequency : 98MHz
Modulation :
Except G, IT: 1kHz, 75kHz deviation ;
(100%)
G, IT: 1kHz, 40kHz deviation (53%)
Output level: 0.018mV (25dBy)
FM ANTENNA terminal
Procedure:
1. Tune the set to 983MHz.
2. - Adjust RV24 so that the TUNED indicator goes on.
©G : German model
IT: Italian model
Carrier frequency : 98MHz
Output level: ImV (60dBx.)
Modulation: L+R
FM Stereo Separation Adjustment
Setting :
BAND switch: FM
FM RF stereo signal
generator vTvM
750 coaxial L/
—
GH FA —o °
1. set
°
FM ANTENNA terminal ere CONTROL 1
33.75kHz deviation
L-R
33.75kHz
deviation
Pilot Signal 19kHz 7.5kHz deviation
Procedure :
Tune the set to 98MHz.
FM stereo
Signal generator pene! aM
Gitpitchaanel connection reading (4B)
LCH | _L-CH ®
®
R-CH | L-CH | Adjust RV21 for
| minimum reading.
R-CH R-CH ©
®
L-CH R-CH Adjust RV21 for
minimum reading.
®-®8
©-O
L-CH Stereo separation
R-CH Stereo separatio:
The separations of both channels should be equal.