If your Philips 50PF9431D/37 comes up with sound, but no image chances are good it has a failed Y-Main board and possibly one or both buffer boards that go with it.
REPAIR KIT FOR LJ92-01275A / LJ92-01436A / BN96-03360A Y-MAIN CAUSING DARK DISPLAY, SOUND, BUT NO IMAGE PROBLEM
The repair kit contains the essential components for repairing a common problem in LJ92-01275A Samsung Y-Main.
REPAIR SERVICE FOR PHILIPS 50PF9431D/37 Y-MAIN SUSTAIN CAUSING SOUND AND NO IMAGE OR SHUTTING DOWN THE TV
We offer repair service for your Samsung Y-Main sustain board