47

PM3394, FLUKE & PHILIPS
ch4
ch3
ch2
ch1
CH1!2.00 V=
CH2!5.00 V=
CH3!2.00 V=
CH4!2.00 V= CHP MTB1.00ms- 0.30dv ch1+
1
2
3
4
T
PM3394, FLUKE & PHILIPS
ch4
ch3
ch2
ch1
CH1!2.00 V=
CH2!5.00 V=
CH3!2.00 V=
CH4!2.00 V= CHP MTB50.0us- 1.58dv ch1+
1
2
3
4
T
Waveform Comm 1 Waveform Comm 2
Laser Servo
After the disc tray is closed (disc chucked/platform up), the laser is turned
on. The laser on command takes this six-step path from IC202:

System Control IC202 and HGA IC601 Communications

After System Control receives the platform up verification (S002 in the
Tray Motor Drive diagram), it gives the command to move the sled to the
home position, then outward. The laser is timed by IC202 to turn on
about the time the sled has already moved away from home position and
is resting under the disc.

HGA IC601 to Servo DSP IC701 Communications

The laser turn on instruction is sent from IC601 to DSP IC701 using the
parallel bus. Since the bus is used by other ICs as well, communication is
valid between these ICs when the CS chip select at IC701/pin 3 is low.

Servo DSP IC701 to RF Amplifier IC001 Communications

The laser turn on command uses three of the four communications lines
that interconnect IC701 and IC001:
The following waveforms show the communications between the two ICs
when PB is pressed. Waveform group “Comm 2” was taken at an ex-
panded time base. They show that SSCK (ch4) is actually the data line
and not the clock. The SSCS (ch 1) marks the 2-byte group of data by
remaining high for 16 bits. SSWD (ch 3) is the clock signal, and not a
write command. These waveforms are only present at disc PB start and
stop.
Laser Life
There are three ways to predict laser life:
qLaser current – Measures the voltage across R005 at Q001/emitter.
New laser = 0.733V. Bad laser will read over 1 volt.
qLaser operating hours – From the test mode adds the CD and DVD
hours. This accumulative information is stored in IC201 EEProm.
qLaser light – 0.18mW was measured using the wrong (freq) laser power
meter (Leader model 8001). 0.35mW of power is the correct power
level using the model 8000 (HeNe position).

DVD/CD Laser Module

The laser turns on when the voltage from CN001/pin 2 = 2 volts. Within
the laser module is a light receiving diode that monitors the laser light
intensity. This voltage is fed back to IC001/pin 19 for regulation. The
voltage is the same for CD and DVD SL PB.
1. System control IC202 2. HGA IC601
3. Servo DSP IC701 4. DVD/CD RF Amplifier IC0
0
5. Q101 6. DVD/CD Laser Module
IC701 – IC001 Communications
Label Location Description
1. SSCS CN002/pin 5 High for 16 bits of data (load)
2. SSRD CN002/pin 6 Not used
3. SSWD CN002/pin 7 Clock
4. SSCK CN002/pin 8 Data
Communications 1 and 2 when the Play button is Pressed
Name Location Voltage/div
Channel 1 SSCS CN002/pin 5 3Vp-p
Channel 2 SSRD CN002/pin 6 0Vp-p
Channel 3 SSWD CN002/pin 7 3Vp-p
Channel 4 SSCK CN002/pin 8 3Vp-p
Time base Comm 1 = 1msec/div. ; Comm 2 = 50usec/div.