Prima LC-20S3 Service Manual page 21

2.2 With picture and without sound when turning on:
Increase the
check whether
channel has no sound
Y
Check whether the signal
output by VCT4993(IC) is
normal
Y
Sound amplifier
peripheral circuit
not work normally
2.3 When receiving TV signal, there is no picture or dark snow:
Confirm the +5V, +32V power supply of TUNER, If they are normal, check whether peripheral circuit
of the TUNER or IF amplifier is normal. If they are all no problem, then VCT4993 or its input signal is
abnormal.
2.4 The power board Troubleshooting guide
2.4.1 The power board of 15":
Power board damages
or fuse blows
Y
Replace N502
volume;
N
Check sound channel of VGA and
every
YPBPR is normal.
VCT4993 (IC) or peripheral circuit
N
does not work normally
or
does
Replace the fuse and check
Y
whether
breakdown
N
Check whether pin1 of N501
has wave
N
Check whether N502
damaged
N
Check N503 and
D504
N901, D501
Y
Replace D502
Check D506 and D505
N
is
Replace N503
Y
D504
19
Y
Replace N501, D501
or