Toshiba W-704C Service Manual page 89

2-2. Servo Circuit
2-2-1. Playback Phase (PG) Adjustment
Test point : P506, P990 (Video Out)
Test equipment : Oscilloscope
1. Playback the alignment tape, press <CH UP> and
<CH DOWN> keys simultaneously to reset to
tracking center.
2. Confirm that phase difference between the rising
edge of DFF 3 pin of P506 and the rise of the CTL
pulse 2 pin of P506 is 25.36 ms.
3. Press STOP key.
4. Press <CH UP> and <CH DOWN> keys
simultaneously on the KDB for at least 5s.
5. Within 2s, press PLAY key on remote control.
6. The display will light up all segments and blink for
10s. Check the luminance which should be
consistent for each grid.
7. During the display blinking, the PG auto head
adjustment is in progress.
1) If the adjustment is successful, it will go to STILL
for 1.2s, and go to PLAY.
2) If the adjustment fails, it goes into the STOP
mode.
8. Confirm that the play indicator is displayed, and
confirm that the falling edge of the DFF pulse is
6.5 H ± 0.5 H (413 µs ± 32 µs) from the V-sync front
edge of the video out signal.
Fig. 2-2-1
DRUM FF
P506 (Pin 3)
VIDEO OUT
P990
6.5H ± 0.5H
CTL PULSE
23.36 ms
2-2-2. Pseudo-V
Test point : Tracking UP-DOWN key
Test equipment : TV monitor
1. Self-recorded tape in SP mode is played and enter
STILL mode.
2. When tracking UP-DOWN key is pressed, the center
of STILL picture should be adjusted with STILL
condition.
Turn off the VCR. When turning off the VCR, pseudo-
V data will be written into EEPROM.
Note :
Do not pull out the POWER CORD, the data will be lost.
2-2-3. SLOW Tracking
Test point : Tracking UP-DOWN key
Test equipment : TV monitor
1. Self-recorded tape in SP mode is played and enter
SLOW mode.
2. When tracking UP-DOWN key is pressed, the
SLOW picture should be adjusted until all the noise
disappear.
3. Repeat step 1 and 2 for SLP self-recorded tape.
4. Turn off the VCR. When turning off the VCR, pseudo-
V data will be written into EEPROM.
Note :
Do not pull out the POWER CORD, the data will be lost.
2-2-4 When IC504 is Replaced
When IC504 is replaced, the data in the VCR is required
to memorize in the new one. So perform the following
procedures.
VCR Status : STOP, EJECT
1. Hold VCR Key Channel Up/Down for 5s during
Power off mode without clock set.
2. And then within 2s, by sending remote control
number key will set the version data as mention
below,
Key "7" – address 12 H = bAH.