Sharp CD-DD4500 Service Manual page 18

CD-DD4500
CD SECTION
• Adjustment
Since this CD system incorporates the following automatic
adjustment functions, readjustment is not needed when
replacing the pickup. Therefore, different PWBs and pickups
can be combined freely.
Each time a disc is changed, these adjustments are
performed automatically. Therefore, playback of each disc
can be performed under optimum conditions.
Items adjusted automatically
(1) Offset adjustment (The offset voltage between the head
amplifier output and the VREF reference voltage is
compensated inside the IC.)
* Focus offset adjustment
* Tracking offset adjustment
(2) Tracking balance adjustment (waveform drawing
Fig.18-2 EFBL)
(3) Gain adjustment (The gain is compensated inside the IC
so that the loop gain at the gain crossover frequency will
be 0 dB.)
* Focus gain adjustment
* Tracking gain adjustment
MAIN PWB
R345
TP301
FM MUTE
LEVEL
T351
AM IF
Figure 18-1 ADJUSTMENT POINTS
CNP301
FM/AM LOOP
ANTENNA
T302
AM
TRACKING fL
AM BAND
VR351
COVERAGE fL
T306
R350
TP302
T
Stopped
CH1=500 mV
DC 10:1
T
FDO
1
TE
3
EFBL
2
=Filter=
Smoothing : ON CH1 :
BW : FULL CH2 :
CH3 :
CH4 :
– 18 –
1999/04/05 20:26:47
CH2=200 mV CH3=1 V 500 ms/div
DC 10:1 DC 10:1 (500 ms/div)
NORM:20 kS/s
=Offset= =Record Length= =Trigger=
0.000 V Main : 100 K Mode : SINGLE
0.000 V Zoom : 2 k Type : EDGE CH1
0.00 V Delay :
Hold off :
0.00 V
Figure 18-2
CH2
v/DIV
200 mV
0.0 ns
0.2 µs