Samsung un32h5203 No Power to Backlight

[realdealthill]

I have a BN44-00768A power supply that gets power,but not to both backlight leads

Checked voltages from Main Board to Power Supply. All Checked Good
I have a Standby light
I see no signs of bullgin/swollen Caps
I see no signs of burnt out components
I have 2 sets of wires that go directly from the PSU to the led strips
With Tv on , and led strips unplugged from PSU. I get 145v on right. and 0v on the left.
I Get the same results with the led strips plugged in also.

[thoma]

Re: Samsung un32h5203 No Power to Backlight



Wait until Get manual appears!!


Disconnect cable mainboard power supply!What happens?

[dick_barton]

Re: Samsung un32h5203 No Power to Backlight

Is the rest of the set working, sound, picture using bright light on screen?

[CapLeaker]

Re: Samsung un32h5203 No Power to Backlight

You have 2 LED strings on CNL802.
You measure 145V on one pair and 0V on the other with the LEDs disconnected? Then there is something wrong with the LED driver circuit.

[budm]

Re: Samsung un32h5203 No Power to Backlight

I have a BN44-00768A power supply that gets power,but not to both backlight leads

Checked voltages from Main Board to Power Supply. All Checked Good
I have a Standby light
I see no signs of bullgin/swollen Caps
I see no signs of burnt out components
I have 2 sets of wires that go directly from the PSU to the led strips
With Tv on , and led strips unplugged from PSU. I get 145v on right. and 0v on the left.
I Get the same results with the led strips plugged in also.

Are you measuring the Voltage at the LED connector with the black probe to the chassis GND?
Pictures provided by shopjimmy.
http://www.shopjimmy.com/samsung-bn4...led-board.htm#

[realdealthill]

Re: Samsung un32h5203 No Power to Backlight

I get an image, no backlight
Tried with mainboard dissconnect, just the same results
I used the the chassie as ground when checking voltage
Where is my led driver?

[budm]

Re: Samsung un32h5203 No Power to Backlight

https://www.badcaps.net/forum/attach...0&d=1485273273
Top left is the LED power supply/control circuit.
The LEDs are connected in series so when you disconnect the LED connector you will only get the Voltage reading on pin 1 only (that is the Anode of the LED string).
Right now you have open circuit in the LED string.

[realdealthill]

Re: Samsung un32h5203 No Power to Backlight

Yep. that's what i was thinking. but the only one side getting voltage threw me off. Because there is no board or wires connecting the strips inside the chassis

[budm]

Re: Samsung un32h5203 No Power to Backlight

It will be similar to this panel:
https://www.badcaps.net/forum/showthread.php?t=51251

[realdealthill]

Re: Samsung un32h5203 No Power to Backlight

This is my Panel.

[budm]

Re: Samsung un32h5203 No Power to Backlight

You have 24 LEDs, if I remember correctly on this model, they 6V LED (DUAL LED in one package).
As you can see, you have two wires per strip and they are terminated in series connection at the LED connector on the power supply board.

[CapLeaker]

Re: Samsung un32h5203 No Power to Backlight

Weird setup. Never had seen a termination like that.

[tdis]

Re: Samsung un32h5203 No Power to Backlight

Someone in my building threw out a UHN32H503AF. Outside impression is that it doesn't turn on.

Inside logic board seems to have power. LED D+ signal has ~145 volts vs 94 something volts spec. S+ and S- terminals are tied to each other by the power PCB and at ground potential. There's a scorched spot on the power PCB in the LED area, near a diode, but the diode checks good, and I don't think the FET underneath is zapped, though something on the PCB obviously got very hot.

Am I right in thinking that this model has two LED strips in series, joined by the S+ and S- traces, and that those are at 0v and the D+ too high because the "top" LED string is open?

How exactly does one remove the back raised metal chassis on one of these to get into the LED strip area?

(FWIW I design low voltage electronics and write firmware for a living - so I have the tools including scope and surface mount rework capabilities, but have never worked on an LCD TV before).

[tdis]

Re: Samsung un32h5203 No Power to Backlight

Ah well, got the trashed un32 apart to find several singed looking LEDs.

Alas a flashlight reveals no a picture, but instead many small cracks in the screen.

So whatever the original failure was, it now has at least two and I think my dreams of a "free" monitor are over.

Grabbed the speakers, will probably yank out the LED strips since at least some of the pixels are likely still good, debating if I want the circuit boards as well.