Troubleshooting6-6 Samsung Electronics6-2-5 No VideoSymptom - A normal/cable network analog broadcast screen is blank or abnormal.Major Checklist- Check the antenna connection settings(Antenna 1 - NTSC (Cable), 64QAM, 256QAM, Antenna 2 - NTSC (Air), 8VSB (ATSC))- Check the tuner output signal (CVBS).- Check the power input of the Main board.TroubleshootingProceduresCheck CN1001 pin 2 for +33VConfigure properlyReplace the Main SMPSReplace the Main BoardIs the antenna connection settingproperly configured?

Samsung HPR4272X/XAC Service Manual