Prima PS-42T8 Service Manual page 29

3.With picture but no sound:
Check if the second pin of sound
power amplifier input the signal.
The sound power amplifier or peripheral
circuit has problem. Check power supply,
if the control of SHUTDOWN pin is
normal; if output short-circuited or other
problems that cause protection to work.
4. A certain channel is abnormal
4.1 No picture on AV
Check N602 and
periphery circuit
If the sound power board X908 is output.
No
Yes
Check N907 or
peripheral circuits.
Yes
Check if TV channel is
normal.
No
Yes
Check if
output is normal.
Yes
No
Measure if the sound
input of current channel
of N907 is normal.
Yes
Check different levels of
circuit following input audio
signal channel.
Measure if the AV input
pin of N700 have the
signal input.
No
Check N903 M52797
and periphery
Yes
N700
No
N700 is damaged
27
The sound damaged.
No