UE48JU6000K Main Board BN94-09749Q

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

ok, you're the expert, I'll just leave you with this little tip, the panel is not the backlights, 2 different things.

Didn't understand your last comment. Trying to supply as much info as possible to help myself abd others watching this thread.

[nomoresonys]

Re: UE48JU6000K Main Board BN94-09749Q

#9?

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

Hi, you have bad backlight leds /single led, this is typical situation of recent Samsungs, disconnecting main board reduces current to the leds ,also in faulty ones , that doesn't let to flow too much current that the led manager can accept, remember with a shorted/leaking led higher current flows through it, also because default brightness is less than normal one, disconnecting tcon probably shuts off the image sending, maybe software reduces the amount of brightness (dynamic brightness).. this is my guess..

[alfatv]

Re: UE48JU6000K Main Board BN94-09749Q

Have done as requested tks.
If i remove the Blu_pwm pin the backlights are on full intensity.

OK, this confirms that backlights are turned off by main board.
But it could be because of detected error. There is FAIL_COUNT pin, maybe it's reported through that pin.
Could be brief open circuit in backlights or on PCB.
You can experiment with known good LED strips or light bulb.
LED tester with adjustable current up to few hundred milliamps can help to detect some strange problems with backlight.

[nomoresonys]

Re: UE48JU6000K Main Board BN94-09749Q

well theres one way, tear it down and check the backlights.

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

#9?

Back side.


I will connect a pair of good led strips and check for any differences.

[Storyteller12]

Re: UE48JU6000K Main Board BN94-09749Q

I think everything is fine. The smaller tv has fewer leds and would take less power. Since you have a bigger tv with more lights the main board thinks it’s to much power and shuts it down.

Either leave blu pwm unplugged or get the correct mainboard.

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

Which one would be the control signal that tells the psb how much is the amount of max current for the auto shut off? Commonly in models the threshold level is managed all within psb through feedback resistors..

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

Ana_Dim to ground will decrease the backlight noticeably but still enough. So for a quick cheat fix put Ana_Dim to ground and BL_Pwm pin open which rises to 3.2v.

Probably stopping here. If i woild continue i would try to change TCON to the same one used with the replacement mainboard.

The original main was too expensive and customer wouldn't accept repair unfortunately. I took a chance as found a cheap alternative board and learned quite a lot as well in this thread.
Tks..

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

It is not a full nor professional repair, excuse me sir, you have faulty leds, a well possible return will happen

[nomoresonys]

Re: UE48JU6000K Main Board BN94-09749Q

well there's the whole problem with tvs today and for a while, they make and sell them too cheaply, always EASIER AND CHEAPER to buy a new one than even pay for a decent/fair labor+parts repair.

[Storyteller12]

Re: UE48JU6000K Main Board BN94-09749Q

well there's the whole problem with tvs today and for a while, they make and sell them too cheaply, always EASIER AND CHEAPER to buy a new one than even pay for a decent/fair labor+parts repair.

That's just on cheap TVs though.

Everyone on here that fixes TVs I bet has some top of the line 2-3k Tv they fixed and can tell you the difference between a $600 65” and a $1,800 65”.

But I get that most customers don't have a high dollar set and repair cost with parts out way buying new

[nomoresonys]

Re: UE48JU6000K Main Board BN94-09749Q

If only, most of the samsung including Q samsung tvs are JUNK and they are not cheap in price, more likely cheaply made, this I already knew but there's been some posts here and at various other forums proving same lately, sony is no different, I have worked on tvs of ALL brands and prices, usually turn down the off off brands, just not interested in them, but lately as in last 10 years, there's really been no difference in quality from the off off brands and any samsung or sony junk sold.

[nomoresonys]

Re: UE48JU6000K Main Board BN94-09749Q

Samsung being the KING of JUNK, need proof, don't need to look any further than here, most posts of problematic tvs is samsung by far.

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

It is not a full nor professional repair, excuse me sir, you have faulty leds, a well possible return will happen

Davi.p I have tested with an external set of good LEDS and made no difference. Also the Power supply is equipped with protection circuit that switches OFF leds in case an abnormal current flows.

I know how to do a professional job by replacing with the original Main Board BN and version. But was beyond uneconomical repair.

I have explained to customer why the Backlights settings do not function. The LED voltage is now 96v instead of 104v. With full intensity the back plate was getting hot. With 96v barely warm.

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

I have tested with an external set of good LEDS and made no difference.

This is not a sufficent test, this is for psb testing not led testing!

Also the Power supply is equipped with protection circuit that switches OFF leds in case an abnormal current flows.

By these 2 answers i see the delicate problem of backlight is not enough clear to you..
it is not a matter of bad mainboard, never read these talkings..
you aren't probably trusting me and this is bad because you will have some returns in future..
it is commonly known in tinkerer's environment that common cheap led testers are not enough to fully test backlights, unless you know how to do it, i have no much experience, i know leds must be exposed, tester must be set to very low current, you will have some leds that glows a little and the faulty ones that doesn't glow at all..
i don't know what do you mean for back plate, is that the rear metal chassis? If it heats too much it is another proof some leds are bad.. because with shorted leds, good leds has an higher V than specs on them and overheats..

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

This is not a sufficent test, this is for psb testing not led testing!

By these 2 answers i see the delicate problem of backlight is not enough clear to you..
it is not a matter of bad mainboard, never read these talkings..
you aren't probably trusting me and this is bad because you will have some returns in future..
it is commonly known in tinkerer's environment that common cheap led testers are not enough to fully test backlights, unless you know how to do it, i have no much experience, i know leds must be exposed, tester must be set to very low current, you will have some leds that glows a little and the faulty ones that doesn't glow at all..
i don't know what do you mean for back plate, is that the rear metal chassis? If it heats too much it is another proof some leds are bad.. because with shorted leds, good leds has an higher V than specs on them and overheats..

Hi Davi.p.

From your posts I know that you have superior experience and admire you of helping others including me. English is not my native language so maybe some misunderstanding here.

Am open to suggestions here for my performed LED Test methods:

1) Use the common LED tester that ramped voltage up to 90v only same on each pair. Full Backlight DC voltage is 104v. So here I agree that tester current output is not enough.
2) Tried a similar model but bigger TV. Same results with just a split second burst of LED On.
3) Found a set of good LED Strips (as I always keep good tested strips when replacing complete set just for testing purposes) and had the same problem and exact voltage measurements.

So then my focus went on the main board again ( Original had shorted CPU) knowing I took the risk with difference in BN number although intended for same model UE48JU6000K but mine is UE48JU6000KXZT version 01.

Checked online and found both use a different TCON as shown here. If I manage to get hold of this TV I will purchase the TCON and see what happens. Then I know there is the panel (screen) issue but the service mode has tens of different screens that I can choose . ( I already did this, I got upside down pic on some options)




Re backplate heat: At full intensity (value of 20), the LEDs will get HOT and the back-plate will get hot as witnessed in hundreds of Samsung sets before. I hope you agree on this one as am sure about this. This is one reason why I always reduce the Backlight for all TVs entering my workshop.


After all this added info, do you still think it is an LED problem? Forza Milan

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

I am still elaborating a bit, but 1 still point, can't be a screen fault since it shows image flawlessy, another punctualization, in tinkerer's environment it is commonly assumed that backlight leds fails due to poor leds, poor led heatsinking (this is partially true for me), leds overdriving by ugly and bad manufacturers, this is not the answer for me, i bet for common spikes from the energy suppliers that in fact destroyed also mainboard, i misunderstood your external leds test, so you mean with pwm-blu at 0v them stays on, with all hoooked leds shuts off? i can try to answer this by the same answer i given to you, you have stored some strips from a total strip replacement, since testers are not 100% results sure, you can't assume that strip is ok, i have suggested many times a simple test in italian forums, but they never listened to me, i'm not repairing anymore so i can't do it, i don't know who are interested here in this so i dony waste my time.. if i'm right this can replace normal led tester..

[alltvrepairs]

Re: UE48JU6000K Main Board BN94-09749Q

I am still elaborating a bit, but 1 still point, can't be a screen fault since it shows image flawlessy, another punctualization, in tinkerer's environment it is commonly assumed that backlight leds fails due to poor leds, poor led heatsinking (this is partially true for me), leds overdriving by ugly and bad manufacturers, this is not the answer for me, i bet for common spikes from the energy suppliers that in fact destroyed also mainboard, i misunderstood your external leds test, so you mean with pwm-blu at 0v them stays on, with all hoooked leds shuts off? i can try to answer this by the same answer i given to you, you have stored some strips from a total strip replacement, since testers are not 100% results sure, you can't assume that strip is ok, i have suggested many times a simple test in italian forums, but they never listened to me, i'm not repairing anymore so i can't do it, i don't know who are interested here in this so i dony waste my time.. if i'm right this can replace normal led tester..

I have just purchased a TCON which is paired with my new mainboard. It was cheap enough to try it out. Will update here once it arrives.


destroyed also mainboard
Destroyed from lightning. Surge came from HDMI port.

RE: I have suggested many times a simple test in italian forums
Are you in https://www.plcforum.it/ italian forum? I am as well. I will try to find out more about your method.

you have stored some strips from a total strip replacement
These were actually tested with the TV set itself not with the Tester only.

[Davi.p]

Re: UE48JU6000K Main Board BN94-09749Q

i'm on plcforum.. name Badciaps.. hihihi