Samsung LN32D403E4D. Sound, No Backlight

[ikeoyou]

Hi Badcaps,
I have been trying to repair this tv on my own but could not find any threads on this particular television or boards.

The unit powers on with the audible power indicator, and the screen shows picture under a flashlight. Without a flashlight, the screen is black.

I inspected the PS board for bad caps, but found none. I replaced the inverter board but it still no back light.

I'm looking for guidance on which components to test with a multimeter to figure out what is causing the issue.

Thanks in advance!

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

The white connector to the top right of the power supply board that goes to the main board, can you please list all the labels for each pin and DC Voltage on each one of those pins when TV is ON, the picture is not focused for me to read those pin names.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

i have uploaded a better picture. you should be able to read it now. as for the voltages, ill get on that.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

actually, the top right connector goes to the inverter and the left goes to the main board.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

from top to bottom:
11.33V
12.67V
12.06V
0.00V
0.00V
The next two fluctuate and I am unable to get a stable reading.

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

OK, my mistake then, so on the connector that goes to the main board, what do you get on the BLU_ON pin?

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

5.12v

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

That is kind of high, does it go down to <1V when TV is OFF?

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

Drops to near 0 or 4.1mV

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

OK, the backlights on signal is good. So you never see the screen even flashes on for seconds?
Can you check the DC Voltage right at the two legs of the main cap? It should be >360VDC.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

Nothing on the screen during bootup. No flashes whatsoever.
Main cap voltage at 391V

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

That means the circuit that drives circuit the primary of the inverter transformer is not doing anything even though the 390VDC and the BL_ON are present.
Where did you get the replacement power supply board from?
There is a fuse FM801S tested OK?

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

I havent replaced the power supply board. I replaced the inverter board.
FM801S is good. What are the chances that there are a problem with the actual backlight?

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

OK, sorry about that. Right now I would say the problem is on that power supply board.

[andariego]

Re: Samsung LN32D403E4D. Sound, No Backlight

i have uploaded a better picture. you should be able to read it now. as for the voltages, ill get on that.

You could check out and tell me if the small IC that is circled in red is FAN9530?

[andariego]

Re: Samsung LN32D403E4D. Sound, No Backlight

You could check out and tell me if the small IC that is circled in red is FAN9530?

Sorry Check if is this IC FAN7930B

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

i am unsure what you mean by this.

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

the markings on the chip are from what I can see:
SMUA014
SEM3040
DU1140

[ikeoyou]

Re: Samsung LN32D403E4D. Sound, No Backlight

any other thoughts on what I should look for? all the resistors tested ok. are the capacitors capable of causing the problem even though they appear fine?

[budm]

Re: Samsung LN32D403E4D. Sound, No Backlight

I will have to do lots of circuit tracing using the pictures to see how they are connected using pictures from SJ:
http://www.shopjimmy.com/samsung-bn4...upply-unit.htm
It will be quite time consuming since we do not have the circuit diagram for this power supply board.