Samsung UN32F5500 LED TV Backlight issue

[siddhu]

Hey All,
My Samsung LED TV 2.5 Years old failed to turn on.
Flash light test passed. So the issue is with Backlight.
I need help in further troubleshooting.
Need to check if the led driver output voltage is fine.
Then to check the led strips.
I dont want to go back to samsung service center again, their charges costs almost a new TV.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Please let me know how to check the output voltage of led driver.
If you want i can post few pics of my tv circuit.

[ReeceyBurger123]

Re: Samsung UN32F5500 LED TV Backlight issue

Hmm possibly led bulb failure, can you take pictures of the back of the tv and all of the boards thank you.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Full back panel circuits

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Tcon and Main board.
Based on the symptoms, I hope these boards are fine.
If required i can provide few more close up pics of these.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

PS board and terminals

[budm]

Re: Samsung UN32F5500 LED TV Backlight issue

Check the solder joints really well on that power supply/LED driver board, especially around the transformers' legs.
The connector for the LEDs, did you pull the off form the panel?
Testing the DCV at the LEDs connector:
Put black probe on the chassis, keep read probe on one pin of the connector, then turn on the TV and see how high the Voltage goes up to and if it drops down later, repeat the same procedure on all of the pins (except the N.C. pin) of the LEDs connector. MAKE SURE to write down the pin's name next to the Voltage readings so we can see which one does not look right.
What is the power supply/LED driver board P/N? BN44-XXXXX?
It looks like the panel uses 4 LED strings.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

hey budm, Solder joints seems firmly well.
Yes i did remove the led connectors to remove the board from chassis.
P/N number is BN4400606BSE38D4FS884
When i checked the DCV at LED connector:
only on pin 12 i get 200-220 V
Rest all 0.
2pins says IF1 and IF2: what are those?

[budm]

Re: Samsung UN32F5500 LED TV Backlight issue

hey budm, Solder joints seems firmly well.
Yes i did remove the led connectors to remove the board from chassis.
P/N number is BN4400606BSE38D4FS884
When i checked the DCV at LED connector:
only on pin 12 i get 200-220 V
Rest all 0.
2pins says IF1 and IF2: what are those?

So far it looks like you have open circuit in the LED strings.

IF1, IF2 are not used and not connected to anything.
The LED strings are connected in series so one LED goes out the whole string will be dead.
BN44-00605 is basically the same as BN44-00606.
Pin 12 is the ANODE of the first LED strings and it is connected to the output of the boost converter B+ output. The CATHODE of the last LED string is connected to pin 3 which is connected to the Drain pin of the SMD PWM CONTROLLED POWER MOSFET, the SOURCE pin of the MOSFET is connected to the current sensing resistor, the other end of the resistor is then connected to the Ground return.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

So now where is the problem?
What should i do now?
Please advise.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

What about pin 10, 6 and 4? Am i supposed to get voltages in those as well?
Or the output voltage is fine?

[budm]

Re: Samsung UN32F5500 LED TV Backlight issue

What about pin 10, 6 and 4? Am i supposed to get voltages in those as well?
Or the output voltage is fine?

As I indicated earlier, the LED strings are connected in series so when you have open circuit in the '1' string, the '2', '3', or '4' string is not going to get any Voltage. It is like Christmas lights, one bulb burnt out then the whole sting is dead.
LED '1' string is the first one of the series of the 4 LED strings.

[budm]

Re: Samsung UN32F5500 LED TV Backlight issue

So now where is the problem?
What should i do now?
Please advise.

You have to open up the panel and check the connectors, the wirings, the LED inside the panel.
Some one else can also chime in if they have other suggestions.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Am little confused.
When i read the voltage value, i kept the led driver connector unplugged.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Let me know whr the voltage from Pin 12 is fine and 0 V from pin 4, 6, 10 is expected.
Only if the o/p voltages from LED drivers are fine i will have to further troubleshoot with LED strips, Right?

[budm]

Re: Samsung UN32F5500 LED TV Backlight issue

Let me know whr the voltage from Pin 12 is fine and 0 V from pin 4, 6, 10 is expected.
Only if the o/p voltages from LED drivers are fine i will have to further troubleshoot with LED strips, Right?

Like I said many many times, the LED strings are connected in SERIES, IF THE FIRST STRING HAS OPEN CIRCUIT, THEN OTHER 3 STRINGS WILL NOT GET ANY VOLTAGE.

'Am little confused.
When i read the voltage value, i kept the led driver connector unplugged.' You must have the LED connector plugged in!

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Hi, I have removed all the boards from the panel, i dont know how to further tear down to reach to the led strips. please guide me on this.

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

When i turn on my tv, the receiver led flashes 5 times, is this any kind of error codes?

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

when i have the led connectors plugged in, i get the voltages as below:
pin 12: 200 - 220 V
Pin 10: 180 - 200 V
Pin 6 : 155 - 175 V
Pin 4 : 130 - 150 V

Pin 11: 180 - 200 V
Pin 9 : 150 - 180 V
Pin 5 : 135 - 155 V
Pin 3 : 0 V


Does this mean the 4th strip is gone?

[siddhu]

Re: Samsung UN32F5500 LED TV Backlight issue

Hey, I opened my TV back panel and there are 5 LED strips.
I could see one of those strips is burnt. I have ordered for it, which i will get it in few days...