Testing Samsung Power Board BN9603775A Most common fault: Stuck in Standby Remedy: Replace F9222L IC After replacing the F9222L IC and performing cold checks to the Power Board, across the Mains Smoothing Capacitor and primary MOSFETs, you can check the O/P voltages of the PSU on the workbench with the following procedure. Tools Needed: Multimeter Variable Bench Variable Power Supply (Ohm uses 12V 1.5A) Method: 1/ Attach an Isolated Mains Supply to the Live & Neutral Connector CN801. (Fig 1) 2/ Switch on the isolated mains. (Fig 1) 3/ At CNM801 Pin 2 check for the Standby +5V. This is an EVER voltage used to Power the Main PCB in Standby mode. (Fig 2) 4/ Turn off the Isolated Mains supply. At CNM801, Pin 1, attach the Variable Power Supply. This is the ON/OFF pin used by the micro to turn ON the Power Supply. (Fig 3) 5/ Turn on the Isolated Mains. 6/ Turn on the Variable Power Supply and apply approx. 1V. (Fig 3) 7/ Test for switched voltage: • • • • •
CNM801 Pins 6-8 = +12V (Fig 4) CNM801 Pins 12-14 = +5V (Fig 5) CNM801 Pin 16 = 13V (Fig 6) CNM802 Pins 10-14 = +24V (Fig 7) CNM803 Pins 10-14 = +24V (Fig 8)
This method allows you to check your supply rails before returning the Power Board into the TV for final checking.
Fig 1 CN801 Mains I/P
Fig 3, CNM801 Pin 1 O/O switching
Fig 5, CNM801, Pins 12-14, +5V
Fig 2 CNM801 Pin2, +5V Stby
Fig 4, CNM801 Pins 6-8, +12V
Fig 6, CMN801, Pin 16, +12V
Fig 7, CNM802 Pins 10-14, +24V
Fig 8, CNM803, Pins 10-14, +24V
NOTES When this board is faulty, I test it before replacing the F9222L to make sure that the board is at fault. Usually this board is stuck in Standby and I check it by reading the O/P voltages at CNM802 / CNM803. As shown above they should read +24V. When faulty these read approximately +15V. The switched +12V rail at CNM801 Pins 6-8 also reads low around +7V.