Troubleshooting Samsung UE37d6540 LED Smart TV

[RBa08]

Hi everyone,
After some elaborative reading and searching on this forum and extensive troubleshooting on this TV I decided to ask some help for my device I'm trouble shooting.

I have bought a Samsung LED tv for learning purposes to repair and since I'm really driven to find the fautly component on component level I am not accepting replacing a complete board.

I'm a technician I do electronic repairs on component level as work and am supplied with the common tools for repairs like a proper scope fluke 177 dmm ESR meter lab psu rework soldering station etc etc..
I am learning how a tv works electronically and trying to learn ways to troubleshoot on component level thats why i got stuck at a certain moment in the need for some advise.

well after this short introduction, the set I'm troubleshooting:

Problem: when off: std-by light on continuously/steady, when switched on: blinking std-by light with approx 10sec intervals.

- Model: Samsung LED smart 3D tv UE37d6540 37 inch
- PSU board: p/n bn44 00458b
- mainboard:
general PCB number:BN41-01587 (silk screen printed on pcb)
specific pn for TV: BN94-05035D (probably a s/w #)

- diagnoses:
-PSU-mainbord disconnected: backlights on - PSU board seems o.k
-A5V (std-by) always present
-when switching the TV to ON with the power button all the voltages are being enabled and measured on CN201 [mainboard connector --> PSU board] EXCEPT 2 voltages which are suspicious: BLU-ON and OD ON/OFF
-disconnecting TCON ribbon, no change
-after switching TV on:
BLU-ON [backlight on] voltage: 0.136V -> should be: +/-5V more of less
OD ON/OFF 1.85V (cannot confirm if 1.85V=o.k?)

CN201 connector pin-out:
[1] B5V [11]B13V
[2]Power ON/OFF [12]B13V
[3]B5V [13]B13V
[4]A5V [14]PWM_DIM1
[5]GND [15]GND
[6]GND [16]PWM_DIM2
[7]Yamp [17]OD ON/OFF
[8]GND [18]PWM_DIM3
[9]Yamp [19]PWM_DIM3
[10]BLU_ON/OFF [20]PWM_DIM4


conclusion: PSU seems ok, mainboard bad. BLU-ON supply line at fault.
I'm a bit stuck in the woods from here, I tried connecting 5V externally to this line heating up a little smd transistor, after measuring this transistor it measures o.k

photo's of the board: https://photos.app.goo.gl/HjiSnhEWhHPYJJEp6
anyone any idea?
any known failing caps for these samsung mainboards maybe?
measuring from CN201 BLU-ON it leads to the upper right of the board

[Andrew F. Ali]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

The BGA chip on the Main Bd. could be causing you problem. Either there is a regulator on the Main Bd. giving the issue. Clear focused photos of the front and back of the Main Bd. and a back view to see how the boards are connected would be helpful.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

The BGA chip on the Main Bd. could be causing you problem. Either there is a regulator on the Main Bd. giving the issue. Clear focused photos of the front and back of the Main Bd. and a back view to see how the boards are connected would be helpful.

a BGA problem would mean unfixable..
- regulators measure all good, however only only 1 lower left corner has a big drop, in: 12.06V - out: 5.05V p/n 7805AF

- the Samsung BGA chip lower left under the silver-colored Samsung main processor, closest to the sticker gets warm but not too warm to touch.

I made some extra photos:

[Andrew F. Ali]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

The reading on the 7805AF is good.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

The reading on the 7805AF is good.

I'm thinking what about the EEPROM, could be corrupt? any ways of diagnosing correct behaviour?

I don't have a schematic for this board unfortionately, I cannot see where the BLU-ON is generated.

[Andrew F. Ali]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

I can't download your pics. Did you post them as jpegs??

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

yes as JPG's I uploaded all photo's made on gdrive here:
https://photos.google.com/share/AF1Q...E4blhOZGs2d0J3
here you can download original size.
the ones above are on photobucket but are resized.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

btw I forgot to add:
- with intervals of about +/-40sec the power supply ticks off and immediately on again.
- checked with the scope on all crystals running.

[Moreno83]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

You need to add photo's via advanced/paper clip button.
When the EEPROM fails or is corrupt it is usually a bootloop problem. ( turning on/off etc)

Good thing you got yourself a new hobby! There is not much to learn from these LED tv's in just diagnosing the problem. You did the basics with just using your brain.
PSU + LED is ok but you got a mainboard with MAYBE a bad EEPROM but probably bad bga. All these D5000/6000/7000 have the same problem.

You can temporary fix it with reflowing the cpu. Add some flux and use a heatgun. Watch out because the board is so thin it will bend easily........
Mine lasted about 2 months but ended up buying a second hand board.

[Moreno83]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

You could reset the EEPROM and/or freeze the EEPROM ( Can with air upside down ).

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

You need to add photo's via advanced/paper clip button.
When the EEPROM fails or is corrupt it is usually a bootloop problem. ( turning on/off etc)

Good thing you got yourself a new hobby! There is not much to learn from these LED tv's in just diagnosing the problem. You did the basics with just using your brain.
PSU + LED is ok but you got a mainboard with MAYBE a bad EEPROM but probably bad bga. All these D5000/6000/7000 have the same problem.

You can temporary fix it with reflowing the cpu. Add some flux and use a heatgun. Watch out because the board is so thin it will bend easily........
Mine lasted about 2 months but ended up buying a second hand board.

Hi Moreno83 thanks for that advise! so you got a set/sets with the same problem as i described is that right? (low BLU-ON signal) I got a few questions in return on that:
-the cpu on this board is the silver-colored main IC right, will reheating do the job and does it has a cover to be removed first etc?
-I could try resetting the EEPROM first, what is the reset voltage, 5V probably. and doesn't it need firmware to be programmed since its an eeprom or does the cpu program it?

[Moreno83]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

I once bought a defective set ( D5000 ) with the same problem. It runs for a few mins and shuts down or restarts. I reflowed the main cpu on the mainboard with hot air + flux. It worked for a while.....

5v will do but you need to short 2 pins together.

EEPROM RESET FOR D60xx/61xx/62xx/63xx/64xx/65xx/66xx/67xx/68xx

https://wiki.samygo.tv/index.php/UnB...y_EEPROM_Reset

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

I once bought a defective set ( D5000 ) with the same problem. It runs for a few mins and shuts down or restarts. I reflowed the main cpu on the mainboard with hot air + flux. It worked for a while.....

5v will do but you need to short 2 pins together.

EEPROM RESET FOR D60xx/61xx/62xx/63xx/64xx/65xx/66xx/67xx/68xx

https://wiki.samygo.tv/index.php/UnB...y_EEPROM_Reset

I connected the SDA line with RESET shown here:
https://wiki.samygo.tv/index.php?tit...PROM_Reset.jpg
no luck, still 0.138V at BLU-ON

I tried connecting the reset to GND, nothing
no luck, still 0.138V at BLU-ON

Looking closely at your diagnoses you did with your tv it seems different to mine, you say yours switches on and off however mine does not switch on at all (low BLU-ON voltage) leaving me to think it's not the EEPROM..

thank for the service manual btw, I went through it but cannot find any schematics to trace that BLU-ON signal, only flowcharts seen in there. still in the woods..

something else, did you reflow with an ordinairy hotair?

[Davi.p]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

Leave to stay the BLU-on signal, it is produced by the cpu but if the software detects a problem it doesn't pull on the backlight (Back Light Unit-ON), the first thing to do is to check all the regulators on the mainb. , you've found the linear ones, are you able to localize the smps ones? The output voltages are often the commons, the pictures are not big enough for me to see..

[angelos]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

Just a quick question. Have you tried to force the back light circuit on to see whether your back light LED's are ok?
My Samsung smart tv when switched on initially before picture is visible on the tv the front panel LED flashes at a rate of 1 pulse per 2 seconds but when the image appears some seconds after that the LED switches off. What if your back lights are at fault?
You could try unplugging the cable going to the main board. On some sets that enables the back lights to come on immediately.
On some other designs you would need to force the BLU-ON pin with a +5V thru a 1k resistor. If i does not come on you could have faulty LED's or even a faulty LED driver on PSU.

[angelos]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

This test requires you disconnect the main completely and force the PSU's BLU-ON circuit "ON" so that you confirm that the LED driver works. You should be able to see the panel light up slightly albeit that the screen is dark. Sometimes thru small holes in the back cover you will see the light coming through.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

Leave to stay the BLU-on signal, it is produced by the cpu but if the software detects a problem it doesn't pull on the backlight (Back Light Unit-ON), the first thing to do is to check all the regulators on the mainb. , you've found the linear ones, are you able to localize the smps ones? The output voltages are often the commons, the pictures are not big enough for me to see..

I am just focusing on this signal so much because it does switches on all the other voltages which is suspicious.

dd you go to this page, it has all the photo's full size:
https://photos.google.com/share/AF1Q...E4blhOZGs2d0J3

are you able to localize the smps ones

Measured the spools and indeed the regulators, if you can point out any other voltages to inspect I'd be happy to do that.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

Just a quick question. Have you tried to force the back light circuit on to see whether your back light LED's are ok?
My Samsung smart tv when switched on initially before picture is visible on the tv the front panel LED flashes at a rate of 1 pulse per 2 seconds but when the image appears some seconds after that the LED switches off. What if your back lights are at fault?
You could try unplugging the cable going to the main board. On some sets that enables the back lights to come on immediately.
On some other designs you would need to force the BLU-ON pin with a +5V thru a 1k resistor. If i does not come on you could have faulty LED's or even a faulty LED driver on PSU.

Yes, as stated in my OP I have disconnected the mainboard from the smps and all the backlight turn on.

I have already tried to put 5V on the BLU-ON line but nothing happens except for it heats up a smd transistor -when switched on by the mainboard- switching the 5V to ground that way.

[RBa08]

Re: Troubleshooting Samsung UE37d6540 LED Smart TV

Reflowing the BGA what Moreno en Andrew pointed out to will be the next step I am going to do. will need some time to prepare because i have never done such a thing