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..

[ChristianBr01]

Hello Davi.p,
forgot to attach some pictures of the One Connect Box and the One Connect Cable that I write about, sorry for that.
The TV has only one connection on the back and this is for the One Connect Cable. This model of the One Connect Box provides the TV with everything it needs over the One Connect Cable. Have attached some pictures of my model from a tear down clip that I found on youtube. It's from a 43 inch model but the Box is the same.
There are 3 Mosfets on the mainboard and about 5 on the BL PSU and non of them is shorted. But one on the mainboard, a P-Ch 30V 50A, doesn't do what it should do, at least I think. I will take a closer look on it and the components around it.

[ChristianBr01]

I borrowed from the company I work for a UNI-T 260A thermal camera. I was really excited but my attempt to find the faulty component went terribly wrong.
I found a spot on the board where something was heating up but very slowly. The Connect Box tries to turn the TV on and then stops. So I've pushed the TV on button for about 4- 5 times to localize the heat spot better.
And then.... something lightens up so quickly that I could not react. This feels so bad. I am really shocked till now. Not what I wanted.
The good is, the PCB is not damaged. I've de-soldered this ic and cleaned everything up. Everything looks good to me but this ic dead. It has a hole now.
Honestly, everything i fixed until now was easy going. A shorted Cap here and a burned Mosfet there or bulgy Cap... This TV is different and shows me how
much I have to learn. A very disappointing and loud "Welcome to the real world!" moment.

Ok... have to order a new one and replace it. IC302 is the one that died. (TPS549A20)

Found a suspicious p-ch Mosfet too. It has 5.1V on source and 5V on Gate but 0V on drain.
In my opinion it should be switched on and has voltage on drain right?
It's a Samsung Mosfet and i can't find a datasheet for it. But found a shop in the Netherlands where i can get it from.😥

[Diah]

wow.. it sound will be big project.. when you remove the IC, you need all ceramic caps around it testing.before you put the new one

[KYBOSH]

Very sorry to hear this but its quite interesting...
If my memory is correct i had a similar looking power management IC die on me with a mac computer i came across about 2 years ago (damaged in a power surge) but it was over 10 years old by that time. Very surprised to see thus happen on 2019 TV but samsung quality cant be compared to apple quality.

You'll definitely need to scout the area for other compromised components.

With regards to the MOSFET, since its a p-channel FET the readings you are seeing are as expected. You see, P-channel MOSFETs turns ON when the gate voltage is sufficiently lower than the source voltage. You will have to look at the datasheet to see how low the VGS needs to be in order turn the FET on. Will definitely be greater than a 0.1v difference.

We also cannot rule out the possibility of a short on the panel itself although i have never heard of one on these FRAME TVs. In reality there is no reason why they should be any different from other Samsung panels. The only real difference is the matt coating which reduces glare. So it should be as susceptible as any other panel. There are just fewer FRAME TVs out there and their owners are less likely to attempt a fix and more likely to just replace the TV.

[Davi.p]

.

[ChristianBr01]

Thank you all for your reply. Have ordered the burned IC and now I am waiting for it.
Have checked the entire region around the chip for short but couldn't find anything else. Hope this was the only defective IC.
Thanks a lot for the information an the p-ch FET. I couldn't find a datasheet for this Samsung MOSFET.

Samsung's quality decreases, that's right. I follow some youtube repair channels and try to learn from them. They are talking quite a lot about
the decreasing quality and how the manufacturer over complicating the circuits/systems.For a beginner like me, this Samsung TV is really complicated, but a really nice one too.
I hope so much that I can fix it.

[Davi.p]

the mosfet is ok, what is odd is that you haven't all voltages, but you have the ps-on active.. or better, you need to test both power boards alone, the fact is that.it is very strange design this, two power supply why? It' helpful if you show the OCB power supply output signals..

[ChristianBr01]

Got my ICs yesterday. Incredible fast shipping via FedEx but incredible shipping fees too. Couldn't await to solder the new IC
on the board and so I did yesterday evening. Checked everything twice for shorts once again... nothing!
Then I've plugt the Connect Box and standby light appeared back again. First I measured all the Voltages on the Board and this
time I got my 5V, 3.3V, 1.9V, 0.9V and 12.8V on the transistors :-

Pushed the power on button and the Connect Box started to click.. and nothing more. Same like before but with all needed Voltages on the Main board.
One fault fixed and a new one appeared. What a pain😖

The second 13V from the Backlight PSU are not where they should be. The PSU is not powering on.
No Voltage on the primary side of the transformer, no Voltage on the secondary side... that simple.

350V on the capacitors and on the Mosfet driver, but no Voltage at the Mosfet gates. Everything was fine there exept the IC. It got the needed Voltage but had no functionality.
It's Fuji Electric FA6B19N and it was dead... Found a similar IC, a FA6B22N on a junk board that I used for practice soldering with my hot air station that I bought last year.
Checked the datasheets at Fuji Electric and both IC are nearly identical. The newer one has internally some additional features but will do the job like the old did.

Swapped the IC and checked everything on the PSU once again for faults... nothing 😀
Reassembled everything and pushed the power on button. TV turns on and off in a loop.... Looks like a faulty panel😢
Disconnected a ribbon cable that goes from the Main Board to the Panel and then - fired it up -

TV has turned on but with a loud buzzing noise from the backlight on no picture. The backlight is only on the right side and the left side stays dark. A
A backlight Mosfet resistor is getting really hot and smells then really bad. I think the left backlight strip is shorted and the Panel is faulty too.

I can't express in words how angry and disappointed I am. I went to bed early in the morning because I didn't feel like continuing. 😑😭

[Diah]

hmm, after your IC replacement you should go back to my first posts # 5 & #7 to avoid other damage.