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EYE-PATTERN SIGNAL – JITTER MEASUREMENT
Measure the signal on the input of the Signal processor
using an analog oscilloscope. Please find the exact
measuring point in your Service Manual.
EYE-PATTERN
800mVpp
TB = 0.5µs/div
HF-Amplifier
+5V_HF
2,4V
7876
2883
3903
3904
BC847B
3901
3K3
3K3
470n
1,8V
Σ (A-D)
560R
1,2V
470R
3906
2881
0,65V
560p
7877
BC847B
See below examples of the signal. Amplitude should read at
least 700mVpp using SBC444A.
good
bad
If the oscilloscope shows a signal like the 'bad' one, and/or
the amplitude decreases within 1 minute - the CD drive has
to be replaced.
5
11
D4
D3
10
D3
D2
9
D2
D1
8
D1
3893
VrefCD10
VREF GE
7
VRIN
470R
3895
6
IREF
27K
3896
+3.3V
5
VDDA1
100R
4
VSSA1
3
ISLICE
2813
3898
2
HFIN
HFIN
220R
4n7
1
HFREF
LD
ON
64
LD
ON
to 3826,3827
3899
2,6V
CD_DA: 0V / CD_RW: 3V
2K7
3923
7878
+3.3V
BC847B
10K
Sanyo
DA12T3
Drive detection
Service Newsletter 2002 – BCU Audio
1-4
CD DRIVE – LASER CURRENT MEASUREMENT
The laser current can be measured as a voltage drop on a
resistor. The resistor is marked in every Service Manual.
The value depends on the type of CD drive.
typical value
VAMxxxx
: 150-230mV
MCDxx
: 170-230mV
DA1x
: 210-250mV
DA2x
: 175-200mV
Use SBC444A (CD-DA) for measurement.
+5V_HF
3,9V
2V
LASER DIODE
CD DRIVE – OFFSET MEASUREMENT
The photodiodes of the CD-drive may have an offset. These
offsets have to be compensated by the signal processor.
High offsets can lead to poor playability of some CDs
(skipping tracks).
To measure the offset values, start the Service Test
Program - section "Focus Test" without a CD.
The offsets can be measured with a DC Millivoltmeter
directly on the connector (see drawing below). Pin
numbering varies from drive to drive.
The values from diode A-D should read 0±10mV.
Diodes E and F are less critical.
CD Drive
Sanyo DA12T3
VREF
VCC
E
E
D
B
A
A
C
D
B
F
C
F
GND
If one of the offsets is higher than ±10mV the CD drive has
to be replaced. Otherwise replace the Signal Processor.
6
most probably defect
≥350mV
≥300mV
≥350mV
≥250mV
Laser power control
U >250mV
->Laser damaged !
3820
+5V
4R7
7811-A
8
LM358D
3823
3,3V
1
3V
7879
1K
BC807-40
4
7
1800
16
VrefCD10
15
+5V_HF
14
E
13
D
12
A
11
B
10
C
9
F
8
4,6V
3
0,17V
2
0,17V
E
D
A
B
C
F
4/4
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