Changhong Electric PT4216 Service Manual page 36

four、no picture：
No picture only VGA
or YPbPr mode
Check GM1501 L4?
L3 pin horizon and
vertical sync waveform
is normal or not?
Yes
1? Check R,G,B input
waveform of
GM1501 is ok or not
2? Check U305,
U306, U307 is ok or
not
Check U310 input
and output sync.
No waveform of sync
regulating circuit
is normal or not
input
abnorma
l
Check VGA jack
Check power supply
and peripheral circuit of
sync regulating circuit
are normal or not ?
Check if there is anyone
normal picture to display
when source switches
No picture only
output
1? Check signal source
abnormal
2? Check DVI socket
Use oscillograph
to check GM1501
DVI LVDS signal
input is normal or
36
Other part is on
next page
DVI
yes
not