LED TV Samsung The Frame 55 inch QE55LS03RAU Standby Light only

[ChristianBr01]

Hello everyone,
I got a Samsung The Frame 55 inch TV for free from uncle cause it is not turning on anymore. I am in the second year of training as an electrician so I have knowledge already but I am far away from to be a pro.
The TV has Standby but ist not turning on. A Friend of mine owns a 50 inch Frame TV so I checked the One Connect Box and the One Connect Cable there. Both are good and working normally. I have opened the TV case and measured some voltages on the Board.
What I already found is that the 12.8V are not an the connector to the main board connector to the power board. The main power supply is in the one connect box and it delivers 350V and 13V over the One Connect Cable to the main board and then to a smaller power supply in the TV.
It is not the easiest TV to start with 🤔

What is happening when i press the TV on Button:
1. Standby Light goes off
2. The One Connect Box starts up with a clicking noise (3 times followed by a break and then another clicking noise for 3 times)
3. Standby Light is back but screen stays black and no backlight at all

The power supply board gets the power on voltage of 3.3V and the 350V but no 13V(12.8V). I found a component on the main board without a value( OL on the multimeter) and I don't know what it is. It is marked as VT and is green. Could it be a smd thermistor? Picture attached for the main board and the component.
What I know is that the missing 13V should reach this point but the don't. Could someone help me to identify this component and the right value?

Thanks a lot!
Christian

[ChristianBr01]

Marked as VT294 on the pcb.

[Diah]

its look some one play with solder IC 1503 SPI 25Q40CL, this is where the start firmware saved on it... check pin 4 if it had short with pin 3 and if there 3.3V on pin 8, try to dump it and posted over here to check if its fine or not

[ChristianBr01]

Hello Diah,
no short on IC 1503
Voltages on Pins

P1: 3.3V - P2: 1 - 1.5V depends on clicking inside the One Connect Box

P3: 0V - P4: GND

P5: 0V - P6: 0 - 0.7V depends on clicking inside the One Connect Box

P7: 3.3V - P8: 3.3V

Thank you for your help!

I thought, i found something shorted but I was wrong. On the picture with the whole pcb are 3 yellow marks. A Coil and 2 ICs. The coil ist connected with on side to a diode and with the other to ground.. so it´s ok.
On the left ist a small sot23-6 IC1100 (U9AJ) where pin 2 and 3 are grounded and after a closer look on them, it´s ok.
On the right side is an IC - IC801(S24C51 - 2C4KJ6) where pin 1 - 4 are grounded. Looks also ok...
Have to correct myself on Pin 2. The Voltage is fluctuating between 1 - 1.9V. The other Voltages are stable.

[Diah]

put jumper between this 2 points FB_TRDY1 and FB_TRDY3, and disconnect the LVDS cable both or one by one.. see if the TV start on

[ChristianBr01]

Tried all combinations but result remained the same.The 13V on the connector are missing and therefore on the psu.
Thank you!

[Diah]

Tried all combinations but result remained the same.The 13V on the connector are missing and therefore on the psu.
Thank you!

then since this TV edge LED BL, in this case each LED unit bulit in protection zener Diode, if one got shorted will effect the PSU shut down.. i would suggest to test BL, before we go deep in HW at boards

[KYBOSH]

Apparently this light comes on when the TV is completely off (not in picture mode).

Have you checked all the fuses on the board? I didnt see any mention of that.
May have a shorted SMD somewhere. Do you have access to a FLIR? You maybe able to see it heatup upon startup.


i havent seen any reports of a shorted display or things like that.
since you ruled out the backights, the cable and the OCB then the only other thing it could be is that mainboard. TV is too new (IMO) for firmware corruption but thats not out of the question.
if you can find a comparable mainboard 55LS03Rxxx that would be awesome. Or convince your friend to let you 'borrow' his display for the weekend...

[Davi.p]

Hi, VT is a varistor.or the like, and it measures ok, don't mind it, you need, as always when missing psb output or others doubts, test the psb inside the OCB with dummy loads, first ensure that detaching it from the rest turns it fully on like the common Samsung scheme, then test for the 13v and 350v, with and without a load on the 13v, i guess 350v is the DC from the graetz bridge and feeds a back light led power supply board (psb) on the tv main body, there must be there a PFC boost so 350v turns to 400v, PFC stage can be K.O. and so the psb shuts to standby.. post very bright photos of main psb, front and back..

[ChristianBr01]

First of all thank you so much for your kind support.
I put the Backlight on my list cause I have no Backlight Tester. I am a little bit scared about disassembling everything and "maybe" braking the panel.
es, I checked the fuses and they are good but I will do it once again, to be 100% sure.

@KYBOSH

I have no FLIR but in the company i work we have a UNI-T thermal camera. Maybe I can get it for a weekend and then check the board.
The One Connect Box and the One Connect Cable are both good. Already mentioned that I have checked both on a 50 inch Frame TV and both working normally. The 50 inch Frame is from 22 an therefor newer then my 2018/19 Model.
It's not easy to get a replacement mainboard for this old 55 model. All the mainbords on Ebay are for the newer models and not for LS03. The Connect Box and the Cable are interchangeable between the 43 - 55 models, they have all the same Box with 210W.
But the mainboard in my 55 LS03 has differently placed and partly different connections on the left side.🤔

Davi.p

Thanks for the VT explanation 😀 ok... so i can go on with my search for the fault.
What I did is to disconnect the cable from the mainboard to the BL PSU and then turned everything on. Same result... I really think that the fault is on the mainboard. The BL PSU can not turn on without the missing 13V.
My multimeter shows no shorts... I think something is just dead and doesn't switch anymore even though it should switch some voltages 🤨

[Davi.p]

First sorry, i did not read well the OCB is tested good, what you did not noticed is that there is a standby 13v that is surely present if you have standby led and is called A13v, what i see is that the OCB contains no real power supply or it generates only A13v, otherwise it is not really clear, in the internal psb they are generated B13v rails and the one that feeds the leds booster, i do not see the path of A13v because of a lot shines on the board, maybe A and B 13v are different rails, A comes from the internal main board, or from OCB, on the main psb primary there are two power mosfets, the top one gets feed from B+ and closes it to the transformer and bottom mosfet, this last can be at short or are at short the secondary side power diodes..