Samsung UE58J5200 LED fail repeatedly

[hifiguy]

Hi folks

Has anyone had this before? UE58J5200 no backlights. When stripped to the leds I observed that a number of the leds had blown, ie burnt.

The customer said it crackled when it went off.

Ok so when I saw the damage I thought as a matter of caution to replace the PSU too. When the strips arrived I checked each and every one and they were all good...Changed all the led strips and PSU...It arced immediately and promptly took the leds out! I've cut my losses and the TV is scrap, but I'm just wondering if anyone may have any ideas as to the cause?

Thanks
Geoff

[Andrew F. Ali]

Re: Samsung UE58J5200 LED fail repeatedly

If it was 'new' PSU and LEDs then I can only guess that you connected the LEDs in the wrong direction. If it was 'new' LEDs only then I may be tempted to say PSU destroyed them.

[hifiguy]

Re: Samsung UE58J5200 LED fail repeatedly

Thanks Andrew.

The PSU was a reclaimed one. I'm thinking it may have had the same fault as the original.

We live and sometimes learn.

Geoff

[hifiguy]

Re: Samsung UE58J5200 LED fail repeatedly

For those who might be interested.
The LED strips on this set have connectors for left and right linking. Hard wired them and the edge connectors and that cured the failing.

[Andrew F. Ali]

Re: Samsung UE58J5200 LED fail repeatedly

So the PSUs are OK, then??

[limo]

Re: Samsung UE58J5200 LED fail repeatedly

Hi,

TV: UE58J5200
PSU: BN44-00787A

Backlit: https://sklep-elwron.pl/pl/p/-LED-Sa...H058BGNV1H/116
12 LED rails (6x DMGE-580SMA-R3 , 6x DMGE-580SMB-R3)
LED: 14 (7+7)

Symptoms: no screen / backlit on but dim

CNM803 (under load):
1,3,5,7 (A13V): 12.79V
9 (GND): 0V

CNL802 (under load / without load):
1 (D1+): 350V / 350V
2 (D1+): 350V / 350V
4 (S-): 227V / tbd
6 (S+): 227V / tbd
8 (D2-): 108V / tbd
9 (D2-): 108V / tbd

Are these values on CNL802 pins (especially from 4 to 9) ok?

Board:

[limo]

Re: Samsung UE58J5200 LED fail repeatedly

Next steps:

PSU:
1. Measure resistance and voltage drop on R9162. Calculate current.
2. Measure resistance of two LED channels (without and with load).
3. Measure all CNL802 voltages without load. Compare results with: https://m.youtube.com/watch?v=xyw9AWLwCHU

4. Check MOSFETs / diodes for short (some are checked).
5. Replace leaked CM841 10uF/350V cap (capacitance and resistance is OK now).

T-CON:
1. Check three blue LEDs status (power supply voltage, fuse).

LED:
1. Since I do not have backlit tester and backlit LEDs are faulty (see burned spots on PCB under R9162, Schottky diodes and MOSFETs) I am going to disassembly steel cover to check LEDs.

[R_J]

Re: Samsung UE58J5200 LED fail repeatedly

Start by replacing the bad capacitors, there is at least one that is bulged on top. There may also be a shorted mosfet Q9101c on the back side of the board.

[limo]

Re: Samsung UE58J5200 LED fail repeatedly

Thank you for reply. I appreciate any advice however:
Cap seems to not to be a big problem now (PSU seems to be working but overloaded due to faulty LEDs - that is why TV is turned off).

When Q9101 is faulty (open/short) then there is no A13V so this is not my case but I did not have much time to analyse PCB trace / pads connections (maybe there will be some similarity with BN44-0632A schematic).

[Storyteller12]

Re: Samsung UE58J5200 LED fail repeatedly

Just about all of these 58” Samsungs have bad backlights that need replacing. The leds fail and take out the power supply also. There are a few threads on this

[R_J]

Re: Samsung UE58J5200 LED fail repeatedly

Thank you for reply. I appreciate any advice however:
Cap seems to not to be a big problem now (PSU seems to be working but overloaded due to faulty LEDs - that is why TV is turned off).

When Q9101 is faulty (open/short) then there is no A13V so this is not my case but I did not have much time to analyse PCB trace / pads connections (maybe there will be some similarity with BN44-0632A schematic).

Q9101 is part of the led boost circuit. If it was shorted, it could kill the A13V if open it would not.

[limo]

Re: Samsung UE58J5200 LED fail repeatedly

PSU checked again (MOSFETs and diodes): no shorts
D1 line voltage: 120V
D2 line voltage: 110V

Calculated current on R9162=1.58 Ohm power resistor is 0.115A.

Power voltages on all boards seems to be OK 12.75V, 1.5V, 1.0V depending on circuit and IC).

Backlit: one LED broken (no big deal)


After reassembling screen and replugging two T-CON flex cables there is an image (menu) but with ghosting:


Faulty LCD screen, T-CON board?

Next steps:
1. To reassembly screen again (right side LCD bezel on the picture is not assembled well).
2. To clean pads on all flex tapes.
3. Check flex tapes conductance.

[nomoresonys]

Re: Samsung UE58J5200 LED fail repeatedly

Tape cutoff method may clear it up: https://www.youtube.com/watch?v=pfrRhw7-ZII

[nomoresonys]

Re: Samsung UE58J5200 LED fail repeatedly

Something to try, turn down the backlights see if it clears up any.