The fault is with AKB [Automatic Kine Bias] circuit.
Check the components on EHT return path.
Check components connected to pin number [11] of EHT transformer [T503](NX4751).
Check R514(2K2, R515_L500, R511-15K_R512-22K_R568-4K7_R513-10K_R510-220K_D504&R509-0.47Ohms/2W). check R509 and if it resistor is open, there will be no 200VDC power path to video output section [Picture tube abse card].Check all associated components ot this path for fault. It is best to desolder out one end of each resistor, pull it out a little up from the printed circuit board, and check the resistance.
This is a main circuit path, as the brightness level of the screen changes according to video comes from the chorma IC. Voltage at pin number [11] of line output transformer will vary time to time according to video signal. Cehck this variation, while the set recieves a video signal, whether it is iternal of external. It should vary. This circuit path is connected to pin number [42] of main system control IC, whic functions as ABL [Automatic Brightness Level].
Check the components on EHT return path.
Check components connected to pin number [11] of EHT transformer [T503](NX4751).
Check R514(2K2, R515_L500, R511-15K_R512-22K_R568-4K7_R513-10K_R510-220K_D504&R509-0.47Ohms/2W). check R509 and if it resistor is open, there will be no 200VDC power path to video output section [Picture tube abse card].Check all associated components ot this path for fault. It is best to desolder out one end of each resistor, pull it out a little up from the printed circuit board, and check the resistance.
This is a main circuit path, as the brightness level of the screen changes according to video comes from the chorma IC. Voltage at pin number [11] of line output transformer will vary time to time according to video signal. Cehck this variation, while the set recieves a video signal, whether it is iternal of external. It should vary. This circuit path is connected to pin number [42] of main system control IC, whic functions as ABL [Automatic Brightness Level].
