Hi.
To start you can simply turning the TV off, disconnecting power cable and connected devices. Then restart first the receiver or DVD or whatever device you want to tune in as source, then restart the TV.
This will reset the set. If the source you use is the internal tuner, then do not connect any device before starting tv.
If that does not work, then try using the buttons on the TV panel. Using the Menu button you should be able to select the TV source.
If the menu, and volume button (on the panel on TV do not respond, then the problem is not the remote, but the TV is frozen because of a different fault.
If the problem is that remotes are not working, the first method should fix the input selection. If the TV does not recognize the remote signal, then the IR sensor inside the TV must be replaced.
Here a replacement IR sensor:
PHILIPS 313926802521 LED IR ASSY.
IR sensor replacement must be done by a technician.
If the TV is faulty, then the first thing to do is calling Philips support.
Regards.