Hi, I just want to share the repair of my Samsung HPT5054X-XAC plasma TV with no picture. It will end up repairing the BN96-04881A (LJ92-01452A) main logic control board. I hope it will help someone out there.
The TV sound was working perfectly, but no picture at all. I've checked the various voltages on the power supply and found no VS voltage. After some investigation I found that VS_ON was not present.
I traced down the source of the VS_ON signal to the main logic control board.
Voltage at C2014 was good at 5.3 volt and coming from the power supply through F2001. F2000 was also good.
Voltage at C2097 and C2102 was good at 1.15 volt, and was produced by a SC2541 step down switching regulator (U2007)
Voltage at C2202 was at 1.5 volt, which was too low considering it was produced by a KIA378R033 LDO regulator (U2400, just at the right of the power connector) that was supposed to output 3.3 volt. The input pin 1 was receiving 5.3 volt. The ground was good at pin 3, but the ON/OFF control at pin 5 was too low at 1.17 volt. It needs a minimum of 2 volt to turn on. Pin 5 was supposed to be pulled up by a 10k ohm resistor at position R2200. A voltage detector (KIA7042AF) marked 6P at position U2401 (just below U2400) is supposed to pull down pin 5 to ground (and shut off U2400 if the input voltage goes below 4.2 volt). U2401 was good, but R2200 (just below U2401) was bad. Once this 10k resistor replaced, pin 5 of U2400 was at 4.5 volt, and the regulator turned on producing its 3.3 volt. Good, the board is repaired and is now sending 3.3 volt to the VS_ON pin on the power supply board.
Just to complete the tour of the various power rails, the last regulator on the board is at U2000. It is a FAN1950D25X producing 2.5 volt to C2012 from the 3.3 volt produced by U2400.
I hope this complete power rails troubleshooting on this main logic control board will help someone. The repair should apply to some other boards, including the similar BN96-06125A (LJ92-01452C), BN96-06522A (LJ92-01452D) and BN96-06095A (LJ92-01503A).
The TV sound was working perfectly, but no picture at all. I've checked the various voltages on the power supply and found no VS voltage. After some investigation I found that VS_ON was not present.
I traced down the source of the VS_ON signal to the main logic control board.
Voltage at C2014 was good at 5.3 volt and coming from the power supply through F2001. F2000 was also good.
Voltage at C2097 and C2102 was good at 1.15 volt, and was produced by a SC2541 step down switching regulator (U2007)
Voltage at C2202 was at 1.5 volt, which was too low considering it was produced by a KIA378R033 LDO regulator (U2400, just at the right of the power connector) that was supposed to output 3.3 volt. The input pin 1 was receiving 5.3 volt. The ground was good at pin 3, but the ON/OFF control at pin 5 was too low at 1.17 volt. It needs a minimum of 2 volt to turn on. Pin 5 was supposed to be pulled up by a 10k ohm resistor at position R2200. A voltage detector (KIA7042AF) marked 6P at position U2401 (just below U2400) is supposed to pull down pin 5 to ground (and shut off U2400 if the input voltage goes below 4.2 volt). U2401 was good, but R2200 (just below U2401) was bad. Once this 10k resistor replaced, pin 5 of U2400 was at 4.5 volt, and the regulator turned on producing its 3.3 volt. Good, the board is repaired and is now sending 3.3 volt to the VS_ON pin on the power supply board.
Just to complete the tour of the various power rails, the last regulator on the board is at U2000. It is a FAN1950D25X producing 2.5 volt to C2012 from the 3.3 volt produced by U2400.
I hope this complete power rails troubleshooting on this main logic control board will help someone. The repair should apply to some other boards, including the similar BN96-06125A (LJ92-01452C), BN96-06522A (LJ92-01452D) and BN96-06095A (LJ92-01503A).
Attached Files