Philips DVP520 Service Manual page 18

Remote reception is insensitive or fails.
Remote reception is
insensitive or fails.
Check whether the remote
control works properly.
Yes
Check whether the power
supply voltage to the remote
censor is normal.
Yes
Use an oscilloscope to check whether
there is output waveform from the first pin IR
of the remote censor after pressing button
on the remote control.
Yes
Check whether there is IR
signal on pin 71 of U3
Fix connection
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Go
No
4-9
No
Check battery
No
Check R317 C303 C304
No
U201(PIN 3 - RC waveform)
Yes
Replace U3
IR waveform
Trouble shooting chart