Help diagnosing faulty Samsung TV 32' UE32D5000

[DarkGT]

Greetings. That's my first post here, I hope this is the right section for my question.
I have 11 years old Samsung TV that develop backlight issues week after I decided to update the firmware from 1011 to 1028. Not sure if related considering the age.

At first the backlight would blink and then would start working fine, if I turn off and on the tv the issue will re-appear. I dissemble it and found that none of the caps show any discoloring, leaks or signs for problems. Sound and screen would work fine, only the backlight will blink once every 5 sec or so. I tried to disconnect the main board and check if the screen would stay on with the power supply board as suggested in the internet tutorials, but the screen would do the same thing - blink.
After a while it got worse and the backlight barely turns on now. I checked the connector voltage and on pin 1 it's around 350-370v and it's jumping between that with every blinking cycle. The most strange thing is that the screen would blink more often when I'm probing with my multimeter, suggesting powerboard issue? From the holes I can see that the whole length of the screen lights up, so maybe the LED strips are okay?

I can't disassemble the screen, there seems to be plastic screen with grid matrix that look like leds or some kind of diffuser on the last layer that's glued on the frame.

Any hope that it's fixable in economical way? Can't find any LED backlights strips or powerboards in my country for this model of TV panel.

Open to suggestions, any jumper like JP854 that would force the screen light to stay on?

[CapLeaker]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

Turn the backlights down to 50%. If there is a problem with the LEDs it should stay on. Any mod you do to force the backlights to stay on, just results in the LEDs dying earlier and then it will stay off.

[DarkGT]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

Turn the backlights down to 50%. If there is a problem with the LEDs it should stay on. Any mod you do to force the backlights to stay on, just results in the LEDs dying earlier and then it will stay off.

Not sure if I can do that, since I can't see what's going on on the screen, the flashlight doesn't help much. I would really want to rule out if is backlight or powerboard issue, anything on the board that I can test to verify? I'm newbie, currently reading the articles troubleshooting that are posted in the forum.

[Davi.p]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

Suspected bad caps on the leds elevator circuit or bad soldering on the power diode of same circuit

[DarkGT]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

Suspected bad caps on the leds elevator circuit or bad soldering on the power diode of same circuit

Thanks for the reply Davi, no bad solder joins, all solid and shiny. I did some testing and probing. All diodes beep on only one direction as they should. There is this small black inductor I guess that have very low resistance I have link with image and readings I wrote on it, you can zoom in and tell me if I'm right to suspect it. https://imgur.com/a/7F4jjUx

Schematics of the power board

BTW where is " leds elevator circuit" located? Mainboard or powerboard? If is on the powerboard you can tell where to look based on the picture I shared.

Thanks in advance, it's my only tv and the budget is thigh right now.

[Davi.p]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

The second choice is bad caps, check/replace those on the secondary around 100v..
third choice maybe inside led pool there are bars connected betweem each one, connection can be loose..

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

check voltages of cnm803, neg. probe on metal chassis, check in standby[plugged in power off] take note, leave probes in place, power on take note, report both conditions here for every pin, example power on, standby 0, powered on 3.3 volts, example of testing: https://www.youtube.com/watch?v=XH9GfkGQX1I

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

try heating the caps on the powerboard for a couple minutes with a hairdryer, heat the electrolytic caps right by there connector then try the tv, DON'T wait til it cools down, try it while its still hot, if no joy, try heating the rest of the caps including the blue ones, no joy, try heating the whole board.

[DarkGT]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

check voltages of cnm803, neg. probe on metal chassis, check in standby[plugged in power off] take note, leave probes in place, power on take note, report both conditions here for every pin, example power on, standby 0, powered on 3.3 volts, example of testing: https://www.youtube.com/watch?v=XH9GfkGQX1I

Thanks for the suggestion nomoresonys. Here is the readings I took.
OFF (stand by) Power ON all DC voltages measured
- 0.6v - 13v
- 0.63v - 12.95v
- 0.64v - 12.94v
- o.64v -12.94v
-0.01v - 0.000 (I hope that's the ground pin)
- 0.01v - 5.54v
- 0.00v - 5.54v

I'm not having hair dryer, so I try tomorrow to think of a way to safely heat it.
The backlight should stay on with the main board disconnected, right? My model is not some exception?
Thanks for the suggestions so far guys, keep them coming .
Edit: Video I recorded of the weird behavior when voltage of the backligh is measured https://youtu.be/2nxef4nPk4w

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

can you list all 14 pins according to the map beside it, like power-on, A5, gnd etc, need to know all of them since I have no picture.

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

also basic checks, check all diodes and resistors on top of board for starters, google is your friend if needed.

[Rajnhl]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

try changing capacitors in backlight section, even if they appear good , they become weak over time.

[DarkGT]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

Thanks CapLeaker Davi.p nomoresonys Rajnhl for the help troubleshooting so far. I think Davi was closest to the actual cause of the problem which is : (dramatic pause)....

Bad led chips on the backlight strips, 3 on the left side and 4 of the right bar side. I have dissemble the panel and beat that glue, super thigh screws etc.etc, and got to two led strips model 2011SVS32 _456K _H1 _1CH. When turn on the backlight would flash the left completely (or at least that how it looked), and only half of the right bar. When tested in diode mode with my multimeter as I wrote - 7 in total are the bad light chips.
I guess that would explain this odd behavior? Maybe the power supply sense a short or too high resistance and would briefly try to power them on, sense problem and turn them off ?

I would take more that a month for a replacements to arrive (if at all those chinese sites aren't reliable). Is there any way to bypass the bad led chips like with resistor to fix the flow of electricity, yes I know it's stupid, but will be temp fix until I get replacements.

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

ok, yep thats what usually goes wrong, after installing new backlights be sure to turn them down if you can, to as low as you can stand, makes them last much much longer. They lasted 11 whole years, that's a pretty good run.

[DarkGT]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

ok, yep thats what usually goes wrong, after installing new backlights be sure to turn them down if you can, to as low as you can stand, makes them last much much longer. They lasted 11 whole years, that's a pretty good run.

I will, the replacement will likely not be an OEM, so better safe...
Also I found a repair video on my model that does a resistor modification by adding another one in series to the existing one, the repairman does that to reduce the power to the leds, right? https://www.youtube.com/watch?v=zOTDUOh_3e0 , could I do the same or there is no point doing it?

Also I'm wishing a Happy new year to everyone reading this

[vinceroger69]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

9 out of 10 tvs i have for repair lately are led issues pity china is taking so long to ship replacements to the uk

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

I will, the replacement will likely not be an OEM, so better safe...
Also I found a repair video on my model that does a resistor modification by adding another one in series to the existing one, the repairman does that to reduce the power to the leds, right? https://www.youtube.com/watch?v=zOTDUOh_3e0 , could I do the same or there is no point doing it?

Also I'm wishing a Happy new year to everyone reading this

yes, great mod and not very hard, just need to make sure you deal with the right resistor/s.

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

this smart youtuber does a lot of them: https://www.youtube.com/watch?v=dPu_BeKVONI

[Davi.p]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

If i understand well right bar is connected in series with left one and holds a single faulty led, it works 50% so this tricks the protection, modifying the resistors is not useful when replacing all leds, neither refuncing much the brightness, i think.. leds faults are due to spikes..

[nomoresonys]

Re: Help diagnosing faulty Samsung TV 32' UE32D5000

^^^I disagree and so do many others, a lot of led early death is caused by being over-driven, which the mod addresses, people are NOT doing it just for fun. TomTechTod is a pro and knows exactly WHAT AND WHY he's doing it, the end.