TV LA40B550 - P/S BN44-00264A - No backlight
Gidday folks, I was wondering if anyone has had experience with faults in the inverter section of Samsungs BN44-00264A power supply they'd be willing to share.
I have a LA40B550 TV that uses a BN44-00264A power supply that refuses to power up the back lights when the main board is plugged in. The main board seems fine and responds to all switch and remote commands, and the power supply with integrated inverter circuit, when by itself, runs the lights just fine. Together they fail.
All volts on the connector (5v, 5v stby, 13v, pwm) look fine except the DET_5V line which remains low.
I figure with the DET_5V being pulled low, the processor keeps the inverter on/off line low. The only input to the protect circuit (see image 1 attached) is the out of phase N2 fet driver line and this seems to be set so if there are not enough pulses of enough width, the circuit pulls it low.
Voltages read in situ
Main storage caps is 385v
13v =====+> 12.8v
DET_5V ===> 0.3v
5.3v ======> 5.2v
epwm =====> 1.85v
----------------
Before i start to wire into the board to bring the voltages out to read them (all of this is under the board and cannot be run easily away from the panel), I was wondering if anyone has seen this before?
I do not suspect the pfc as it's running fine without the main board and the voltages on the main caps is good.
I do not suspect the over/under voltage protection circuit because it runs fine without the main board.
I do not suspect the main board, as it's doing what I would expect it to do with that signal.
I do not suspect the ccfls as they all come on without the mainboard.
I am sus on all of the bits around ICI803B. I will sit and measure each of them and then try to read the voltages while its running, but before I use a lot of wire wrap, has anyone seen this before and am I barking up the wrong tree?
I have a LA40B550 TV that uses a BN44-00264A power supply that refuses to power up the back lights when the main board is plugged in. The main board seems fine and responds to all switch and remote commands, and the power supply with integrated inverter circuit, when by itself, runs the lights just fine. Together they fail.
All volts on the connector (5v, 5v stby, 13v, pwm) look fine except the DET_5V line which remains low.
I figure with the DET_5V being pulled low, the processor keeps the inverter on/off line low. The only input to the protect circuit (see image 1 attached) is the out of phase N2 fet driver line and this seems to be set so if there are not enough pulses of enough width, the circuit pulls it low.
Voltages read in situ
Main storage caps is 385v
13v =====+> 12.8v
DET_5V ===> 0.3v
5.3v ======> 5.2v
epwm =====> 1.85v
----------------
Before i start to wire into the board to bring the voltages out to read them (all of this is under the board and cannot be run easily away from the panel), I was wondering if anyone has seen this before?
I do not suspect the pfc as it's running fine without the main board and the voltages on the main caps is good.
I do not suspect the over/under voltage protection circuit because it runs fine without the main board.
I do not suspect the main board, as it's doing what I would expect it to do with that signal.
I do not suspect the ccfls as they all come on without the mainboard.
I am sus on all of the bits around ICI803B. I will sit and measure each of them and then try to read the voltages while its running, but before I use a lot of wire wrap, has anyone seen this before and am I barking up the wrong tree?
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