Samsung un46eh boot loop

[farnswerth]

I was given a samsung un46eh6000 that is stuck in a boot loop. When it is plugged in, it will power on and give me a simple chime noise(I assume the startup sound), then after a few seconds the backlight will flash on for a spilt second, then after another few seconds it will repeat the process. I unplugged the backlight connector from the power supply and powered it back on. I tested all of the electrolytic capacitors I could find on the power board, and they all measured within approx 10% of the rated uf(with a component tester).

Looking online for more answers I came across a post on this forum that mentioned that samsung tvs can go into a boot loop situation when one or more of the leds on the backlight go bad/short/open.

So I unplugged the backlight connector from the power supply and powered it back on. At this point, I can hear the startup sound, just like before. Since the backlight connector is unplugged it does not flash, but it also does not power down and reboot. After 30-60 seconds I pressed the power button on the remote and the tv set powered down(I heard another chime that indicated this tv has a "power down" chime as well).


I disassembled the tv, removed the bezel, screen and diffuser, and powered up the set to check the leds. All of the leds seemed to illuminate during the momentary flash of the boot loop, so I'm unsure of what to check next.

Most of the information I can find online about samsung bootloops seems to direct towards a firmware problem, but the descriptions on those usually talk of a relay click that I do not hear on this set, or otherwise indicate that it's a problem that I am not experiencing(including a few "factory reset" tips and tricks that did not work).

[farnswerth]

Re: Samsung un46eh boot loop

Okay, so after looking some more on this forum for general samsung troubleshooting, I went ahead and measured voltages.

BN44-00498A PSU

Backlight Connector CNL802

D1+ - D1-:
-main board unplugged, Backlight lit up 240v to both.
-All Boards plugged in, over 400v to both at moment of blink.
-backlight unplugged, D1+ - Ground reads 300V to both

S+ - S-
Always reads Zero volts, every condition
S+ - Ground reads Zero volts, every condition

With the led backlight connector plugged in, Measured from D1 to -D1 I get a brief spike of >400 volts, when the backlight blinks on. Remember it only blinks on very briefly then cycles all over again. There is also a loud hum when I do it this way. I'm pretty sure all of this is normal but I'm documenting it anyway.

To Main Board Connector CNM803

Odd Numbered Pins
1. 12.7v
3. 12.7v
5. 12.7v
7. 12.7v
9. 0v
11. 5v
13. 5v

Even Numbered Pins
2. 3v
4. 12.6v
6. 2.8v
8. 0v
10. 5v
12. 3v



This is all I have found as far as what to measure so far, with the exception of a possible fuse on the Tcon board to check, but I have not found it. I have read a few posts that say that the backlight leds and power supply are in working condition if the backling turns on when the main board is unplugged. Is this correct? I should focus on the tcon and main board now right?

[CapLeaker]

Re: Samsung un46eh boot loop

To check the LED's, unplug the PSU from mains, unplug the main board from PSU, then plug the PSU back into mains power. When you do this, the backlights should be on full tilt. After you determent that the LED's are not the problem, you may stand a chance by either flashing new firmware or resetting / replacing the EEPROM on the main board.

[farnswerth]

Re: Samsung un46eh boot loop

To check the LED's, unplug the PSU from mains, unplug the main board from PSU, then plug the PSU back into mains power. When you do this, the backlights should be on full tilt. After you determent that the LED's are not the problem, you may stand a chance by either flashing new firmware or resetting / replacing the EEPROM on the main board.

When the main board is unplugged, it looks like all of the leds are on, although I did not discover this was poosible until after I reassembled the tv, so I am judging this through the dark LCD. SHould I disassemble the tv completely again to check that each individual led is lighting up? The screen looks uniformly lit currently.

[budm]

Re: Samsung un46eh boot loop

If the backlights stay on (as long as TV is plugged into the outlet) when the cable between the main board and the power supply board is disconnected then the backlights are OK.
Is that what you are seeing?

[farnswerth]

Re: Samsung un46eh boot loop

If the backlights stay on (as long as TV is plugged into the outlet) when the cable between the main board and the power supply board is disconnected then the backlights are OK.
Is that what you are seeing?

Yes, with the main board unplugged from psu, the backlight stays on. When everything is plugged in, it boot loops. When the backlight is unplugged from the psu, and the main board is plugged in, the system powers on and stays on, but I cannot tell if anything else is happening, only that it is not boot looping in this configuration.

[farnswerth]

Re: Samsung un46eh boot loop

Also, the fuse on the tcon appears to have continuity and be intact

[budm]

Re: Samsung un46eh boot loop

So your power supply board is BN44-00498A?
I do not see any Backlights ERROR signal pin on the power supply board that goes back to the Main board to tell it to shutdown if there is problem with backlights circuit.

[farnswerth]

Re: Samsung un46eh boot loop

YEah BN44-00498A

I dunno if you need the full number printed on the board, but it's PD46AV1_CSM (BN44_00498A) PSLF930C04A

And the Main BOard is BN94-05758C

[budm]

Re: Samsung un46eh boot loop

Can you check the DC Voltage between the two legs of that main filter cap 82uf 450VDC when everything are hook back up and turned on? I want to see if the Voltage will be steady at around 390VDC or not or if it is fluctuating.
Pictures provided by shopjimmy.

[farnswerth]

Re: Samsung un46eh boot loop

Can you check the DC Voltage between the two legs of that main filter cap 82uf 450VDC when everything are hook back up and turned on? I want to see if the Voltage will be steady at around 390VDC or not or if it is fluctuating.
Pictures provided by shopjimmy.

I checked the voltage with everything plugged in, with just the main board unplugged and with just the backlight unplugged.

With everything plugged in, it hits 390-400, then starts to slowly come down to around 340 before going back up. I believe this is the tv powering down, as it's always right after the lights blink that the voltage decreases, and right before the chime that the voltage increases.

Unplugging the main board shows a constant voltage of 393 volts. Unplugging the backlight shows a constant voltage of 393 volts as well.

[budm]

Re: Samsung un46eh boot loop

I checked the voltage with everything plugged in, with just the main board unplugged and with just the backlight unplugged.

With everything plugged in, it hits 390-400, then starts to slowly come down to around 340 before going back up. I believe this is the tv powering down, as it's always right after the lights blink that the voltage decreases, and right before the chime that the voltage increases.

Unplugging the main board shows a constant voltage of 393 volts. Unplugging the backlight shows a constant voltage of 393 volts as well.

If the it powering down it would have drop down to around 160VDC not 340VDC because when TV is powered down the PFC Voltage booster circuit will be shutdown.
But we still need to know if the control Voltages are also going up and down or not, so monitor POWER ON/OFF pin 14 of the power supply connector to see if it goes up and down in sync with boot loop or not.

[farnswerth]

Re: Samsung un46eh boot loop

If the it powering down it would have drop down to around 160VDC not 340VDC because when TV is powered down the PFC Voltage booster circuit will be shutdown.
But we still need to know if the control Voltages are also going up and down or not, so monitor POWER ON/OFF pin 14 of the power supply connector to see if it goes up and down in sync with boot loop or not.

It's in sync with the boot loop, it reads 3.2v briefly before dropping to zero.

[budm]

Re: Samsung un46eh boot loop

So the PS-ON signal is cycling on and off.
The A5V is steady, right?

[farnswerth]

Re: Samsung un46eh boot loop

So the PS-ON signal is cycling on and off.
The A5V is steady, right?

I believe so, it's pin 12, it has a constant 5v throughout the cycle, no interruption. The rest of the pins cycle with the reboot except pin 12.



Is this the correct pinout?

1. B13v
2. PWM_Dim
3. B13v
4. B13v
5. Vamp
6. BLU_on/off
7. Vamp
8. GND
9. GND
10. GND
11. B5v
12. A5v
13. B5v
14. Power on/off

[diif]

Re: Samsung un46eh boot loop

I have just fixed a Samsung that was in a boot loop. It's a slightly different set with Smart and as well as the EEPROM there was also NAND.
There are some holes neat the EEPROM, join the reset and SDA together and power on the tv, let it power on and reset, then remove the power and remove the join.
I believe when the reset is enabled it loads new firmware from the memory.
It might be a similar arrangement on your TV and work investigating although my TV stayed on for about 5 seconds before restarting.

[farnswerth]

Re: Samsung un46eh boot loop

I have just fixed a Samsung that was in a boot loop. It's a slightly different set with Smart and as well as the EEPROM there was also NAND.
There are some holes neat the EEPROM, join the reset and SDA together and power on the tv, let it power on and reset, then remove the power and remove the join.
I believe when the reset is enabled it loads new firmware from the memory.
It might be a similar arrangement on your TV and work investigating although my TV stayed on for about 5 seconds before restarting.

Awesome, thanks for the tip! I'll have a look and see what I can find.

[thoma]

Re: Samsung un46eh boot loop

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

[farnswerth]

Re: Samsung un46eh boot loop

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

Thank you. I think I found the ic on my board, and it looks like its pretty different than those examples. There is a pinout here, but I can't make out what the order is supposed to be, it's confusing me.

[farnswerth]

Re: Samsung un46eh boot loop

Okay so I tried multiple combinations to jump the eeprom to reset. The last three pin holes look to be (1) M_E_SCL (2) M_E_SDA and (3) M_HRESET. I tried every combination of those three holes but got nothing new to report.

I thought I was on to something with this post Because the last post is a mention of replacing the TCON board fixing the problem, but I misread a few comments before, and it turns out that solution fixed a completely different problem than mine.