Samsung UE42F530 wont turn on

[rtstorm]

Hello,

I have this Samsung UE42F5300 TV that won't turn on, it just splashes backlight for a second and then TV restart, and it does that in a loop.

I check voltages that go to the main board and they are 12V, 5V, 3.3V

But voltages that go into the LED backlight are weird. On one pair it jumps from 0 to 28V but on other two voltage jump from 0 to 98V. When testing LED voltage with disconnected LED's than all voltages are 0V (maybe because there is no load on them?? )

What do you think? Is this a bad LED strips or something with the power supply

[budm]

Re: Samsung UE42F530 wont turn on

We need pictures of the boards and the whole backside of the TV showing all the boards..
What is the power supply/LED driver board P/N/ BN44-??????

[rtstorm]

Re: Samsung UE42F530 wont turn on

Sorry, here is the pics.

[budm]

Re: Samsung UE42F530 wont turn on

OK, you need to test the DC Voltage on the LED connector CNL802, you must keep the connector in place.
1) TV is off, set the meter t0 400VDC (or at 200V scale minimum) scale then keep the meter probes between the two legs of capacitor C9118, then turn the TV on while keeping an eye on the meter to see how high the Voltage goes up up to then wait 10 seconds to see how low it goes down too.
2) Repeat step #1 but now you will move the probes to capacitor C9218.
3) Turn off the TV, then keep black probe on the chassis, keep the red probe on pin 3 (4-) of the connector CNL802 then turn on the TV to see how high the Voltage goes up to then wait 10 seconds to see how low the Voltage goes down to.
4) Repeat step #3 but this time you will move the red probe to pin 9 (2-) of the LED connector.
Report the readings to us.
BTW make sure you count the pin number of the CNL802 correctly.
This board is also known for developing bad solder joints on the component legs that are soldered to through hole rivets.

[rtstorm]

Re: Samsung UE42F530 wont turn on

When I am testing CNL802 connector, does it need to be connected to LED's or not?

[rtstorm]

Re: Samsung UE42F530 wont turn on

On C9118 voltage goes to 230V peak, and get low to 50V.
On C9218 voltage goes to 180V peak, and get low to 99V.

pin 3 (4-) goes from 0V to 44V
pin 9 (2-) goes from 0V to 1.1V

I did not need to wait 10sec because TV try to turn on, but in a second it turns off and then goes in loop of ON/OFF

[budm]

Re: Samsung UE42F530 wont turn on

On C9118 voltage goes to 230V peak, and get low to 50V.
On C9218 voltage goes to 180V peak, and get low to 99V.

pin 3 (4-) goes from 0V to 44V
pin 9 (2-) goes from 0V to 1.1V

I did not need to wait 10sec because TV try to turn on, but in a second it turns off and then goes in loop of ON/OFF

You have open circuit in one of the two strings.
Pin 9 (2-) is the Cathode return of the bad LED string, it has 230VDC feeding the Anode but you do not have much coming out on the Cathode side.

Samsung BN44-00645A
Pictures provided by shopjimmy.

[rtstorm]

Re: Samsung UE42F530 wont turn on

Ok, so I need to disassemble LED strips and check for a shortage?

[budm]

Re: Samsung UE42F530 wont turn on

Ok, so I need to disassemble LED strips and check for a shortage?

Yep, you need to strip it down and test for bad LED/LED's and the connectors on the strips.
BTW, you can also see the Voltage chart printed on your board to tell you what the Voltages should be with loads.