5
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.
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.
6
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 most probably defect
VAMxxxx : 150-230mV t350mV
MCDxx : 170-230mV t300mV
DA1x : 210-250mV t350mV
DA2x : 175-200mV t250mV
Use SBC444A (CD-DA) for measurement.
7
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.
If one of the offsets is higher than ±10mV the CD drive has
to be replaced. Otherwise replace the Signal Processor.
Sanyo DA12T3
CD Drive
A
A
F
C
B
E
C
D
E
VCC
B
VREF
F
D
9
10
11
12
13
14
15
16
1800
+5V_HF
VrefCD10
A
D
E
B
C
F
GND
8
E
D
A
B
C
F
Laser power control
100n
2878
470n
2876
3821
1R
1K
3823
2880
33p
+5V
BC807-40
7879
3817
47R
3820
4R7
47R
3819
1n
2879
2877
47u
1
8
4
7811-A
LM358D
3
2
10K
3822
47R
3818
2841
100n
47n
2869
+5V_HF
LASER DIODE
U >250mV
->Laser damaged !
4,6V
3V
3,3V
3,9V
2V
0,17V
0,17V
Sanyo
DA12T3
HF-Amplifier
D3
D2
D1
To Next Page
Loading...
