Hi, philips (sony and others) uses the flashing red lights to give an error code, but all that means is that a circuit is probably shorted and doesn't always indicate specific components,.
42pf7421 is an LCD that basically has two large circuit boards in it. If you have technical ability you can examine the power supply to see if any capacitors are swollen on their top sections. this is a common failure in many LCDs and Plasmas, but would require soldering to replace them. If no caps look swollen troubleshooting this set would involve voltage checks , a service manual and board replacement.
Could be either the main board, power supply or possibly a bad screen (panel) If you have the set open you can sometimes see the LCD bulbs light for a split second indicating that a problem with either the panel itself or the ballast power section. If it lights for a second sometimes I can see that one bulb is not lighting. One bad bulb will cause the set to go into shutdown mode , indicating a bad screen (panel) .
I hope this info helps you decide on the options before you
1. call a tech expect to pay an estimate fee, parts and labor btwn $200-$1000
2.check the power supply, reseat the panel cable, look for a momentary light of the screen. order a suspected part and replace it yourself.
3. buy a new TV (sry bad option)
hope this helps
Eric I’m happy to help further over the phone at
https://www.6ya.com/expert/eric_ab7c09ec01841771