10-3
4. MEASURE THE LASER CURRENT
CD DRIVE – LASER CURRENT MEASUREMENT
The laser current can be measured as a voltage drop on
resistor 3820. Typical value 170 - 190mV
5. MEASURE THE OFFSETS OF THE CD-DRIVE
CD DRIVE – OFFSET MEASUREMENT
Each photodiode of the CD-drive may have an offset.
This offset has to be compensated by the signal
processor. A high offset of the CD-drive leads to poor
playability of some CDs (skipping tracks).
Start the Service Test Program - section „Focus Test“
without a CD. Focus sensitivity = CD-RW.
Use a DC Millivoltmeter for measurement. The offsets
can be measured direct on the connector. See drawing
below.
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.
6. MEASURE THE OFFSETS OF THE CD10
SIGNAL PROCESSOR – OFFSET MEASUREMENT
Each ADC input of the CD10 may have an offset too.
Also this offset leads (together with the offsets of the CD
Drive) to poor playability of some CDs (skipping tracks).
Start the Service Test Program - section „Focus Test“
using a CD-RW.
Use a DC Millivoltmeter for measurement. The offsets
can be measured on capacitors near the signal
processor. See drawing below.
The value should read 0mV±10mV.
If one of the offsets is higher than ±10mV the signal
processor has to be replaced.
If none of the measured offsets is higher than ±10mV -
replace the part with the higher value.
CD Board Copperside view
D1
D2
D3
D4
R1
R2
V
REF
SIGNAL PROCESSOR
MD
PD-IC
E
C
A
D
B
F
DA23
Vc
Vcc
5
6
7
8
9
1
10
11
12
2
3
4
1800
+5V_
Vref_
E
C
A
D
F
B
Laser power control
2811
220n
LM358D
5
6
7
8
4
7811-B
100n
2878
1n
2879
47R
3819
2880
33p
3821
1R
47R
3818
2877
47u
3822
10K
BC807-40
7879
LASER DIODE
MONITOR DIODE
3823
1K
3817
47R
3820
4R7
3872
100R
+5V_HF
+5V
U >250mV
->Laser damaged !
3,5V
3,3V
4,7V
0
0
Service Hints
Summary of Contents for EMOTIVE Micro MZ-1000
Page 34: ...8 10 TECHNICAL REMARKS ...
