Samsung UN40B6000VM - Black Screen, Rebooting

[paulo_lima]

Hi,

I am just trying to find which board is the corrupted:
TV Model: UN40B6000VM
PSU: PSLF171B01A
Main board: BN41-01184B

The problem: TV is able to power on, plays the melody, but the screen stays black and no backlight, 10 seconds later i hear the relay clicking, she reboots and try to start over and over again. If i disconnect main board backlight works.

The power supply looks nice and measures steady in all voltages the only pins i am not sure are:
DET 5V--------4.9v
E-PWM--------0.5v
BL ON---------0
Vamp 12.8----12.7
POWER ON----0.6
*Power on pin gets voltage spikes (~1.4v in DMM) when relay is clicking -Is it the Main Board telling the PSU to turn off?
*Power on stays 0.6 even with Main Board disconnected.

[CapLeaker]

Re: Samsung UN40B6000VM - Black Screen, Rebooting

BLon= 0

your main board isn't turning your backlight's on. So your problem is on the main board.

[paulo_lima]

Re: Samsung UN40B6000VM - Black Screen, Rebooting

Thank you, i already suspected, but needed to make sure as those boards are expensive in here.
I know the chances of getting this board fixed are very low, but i'm giving a try, starting at looking every buck converter output and regulators.
Any tips are welcome.

[CapLeaker]

Re: Samsung UN40B6000VM - Black Screen, Rebooting

PSon and BLon are generated on the main boards main IC. I suppose you could try to trace the BLon backwards to the main IC.
I never had much success with finding a little faulty part, as it was always the main IC's fault not generating BLon.
You could disconnect the BLon pin from the connector that goes from the main board to the PSU. Try jumping PSon to BLon on the PSU (remember to disconnect that BLon coming from the main board, we don't want to back feed power). See what that does. Alternatively you could take any switched 2V to 5V source, put a 1k ohm resistor in series and put that to the BLon pin on the PSU.