Sony PFM-42X1 Service Manual page 33

3. SCAN IC (Y drv B/D : IC1 to 12) damage
1) If the SCAN IC has a failure, one horizontal line may
not be display on the screen.
. Test point : ICT measurement of GND through Y
drive B/D output.
. Waveform : As shown in Fig. 5.
SCAN pulse does not occur
Fig. 5 When SCAN IC is poor
2) The screen may not be displayed when the SCAN IC is
damaged due to the SCAN IC failure, external electric-
ity or spark.
. Test point : ICT measurement of GND through Y
drive B/D output.
. Waveform : Output waveform is not output (The
damage can be seen in the SCAN IC on
the top or bottom of the Y drive B/D).
3) The screen may fluctuate horizontally when the cable
on the top or bottom of the Y B/D is damaged.
. Test point : ICT measurement of GND through Y
drive B/D output.
. Waveform : As shown in Fig. 6.
Normal scan pulse
Noise occurance at scan section
Fig. 6 When the Y drv B/D top or bottom cable is damaged
PFM-42X1/42X1N
When the internal output FET
of IC is damaged
4) If the SCAN IC output is shorted by a dust or a foreign
substance, two horizontal lines may overlap on screen.
. Test point : ICT measurement of GND through Y
drive B/D.
. Output waveform : As shown in Fig. 7.
Enlarge the scan pulse
Fig. 7 When SCAN ID output is shorted
<SCAN IC normal output wave>
. Measuring position : The enlarged SCAN section after
measuring the output ICT of the Y
drive B/D. (Full White pattern).
Widen the pulse width
Decrease voltage of the
scan pulse
SCAN section
SCAN PULSE
2-13