Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound ok)

[Uranium-235]

This tv has no backlight, no screen image. But the power button blinks on and off normally and responds to remote control commands for on off and blinks for other commands

I plugged in my roku stick and eventually got sound

Driver leds are lit. No visible bad caps but are samwha. Board browned a bit on four resistors (ive seen this common on samsung power boards, same group of resistors).

Voltages to main are all reading steady 13v

[budm]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

1) TV is OFF, ALL connectors in place.
2) Put DC Voltmeter to 200VDC scale
3) Keep Black probe of the meter on the chassis
4) Put red probe on pin 1 of the LED, tuRn the TV on while watching the meter to see how high the meter jump up to, record that reading, and wait 5 seconds to see how low it goes down to, record that reading. Turn TV OFF.
5) Repeat step 4 on the rest of the LED connector's pins.

You MUST report the Pin name and follow by the Voltage reading of each pin of that LED connector so we do not have to guess what each pin is.

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Im guessing this is the led connector.

1 (D+), off: 189, on: 203
2 (D+), on-same as above
3 through 9 off: < 1v
3 through 9 on: < 0.2v

[budm]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Samsung BN44-00769A Power Supply / LED Board

You have open circuit in the LED strings.

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

So the strips are the problem? Never replaced those before. I had a chance to in a 55" Sanyo but the risk of breaking the lcd was too high. This might not be as bad. Any idea where to find the strips?

[budm]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

You need to match the strip to the LCD panel model number, so find the LCD panel number sticker and search for the LED strips based on that model number.
BTW, do you have LED tester? that is a good tool to have.

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

No I don't. But why does the screen itself show no image on the flashlight test?

[Andrew F. Ali]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Sometimes due to ambient lighting the flashlight test seems not to work. Fix the backlights and setup everything and switch on your TV. You WILL see pictures.

[budm]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

No I don't. But why does the screen itself show no image on the flashlight test?

That is why having LED tester will come in handy because you can at least light up the good LED strings.

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

First two are from string 1. Obviously the problem there
Second from string two. Should replace
Third seems fine

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

I mean, the first two pictures are from led strip 1. Third picture are from led strip 2
Led strip three looks fine, but at shopjimmy it's $34 for one or $54 for all three so I should go ahead and replace all three

As far as an led tester, I don't often work on tvs, so I'm not sure the cost is warranted. Aside from bad caps, this is even stretching what I'm willing to do. Larger screens require a suction tool to lift the lcd panel and that is $200+ from china

[Andrew F. Ali]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Good plan...Replace ALL the LED strips with new ones...that will eliminate backlight problems in the near future. Good Luck. As soon as it is possible invest in a LED Backlight Tester. Though it may sit around unused, you will be glad to have it in the not too distant future.

[budm]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Once you get it fixed, make sure to set the backlights level on all input to as low as possible and never put the pictures setting to VIVID mode.

[Uranium-235]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

Worked!

Cracked the fucking panel after putting it back together.

[ajshoe]

Re: Samsung un40h5203. Power board diagnostic (mainboard boot, remote responds, sound

this is why harbor freight suction cups from china were invented !