Samsung un65es8000fxza turns off after 15-20 seconds

[itelite]

Working on a un65es8000fxza with an issue i have not seen before.

Turning on with the power button will turn it on, then after 15 to 20 seconds it will turn off.

If you watch the standby voltage during this process a relay will click, standby is gone, relay clicks again standby is back for a fraction of a second, relay click, gone.

If i unplug cable 20 from between the main board power supply the backlit will turn on and run indefinitely.

Cable 20 has brown discoloration on of the 2 5v standby wires. I flipped cable around to rule out a bad connection (or at least move my bad connection) i also put a ammeter in place of that discolored wire. about half an amp until there isn't.

Unplugged all cables from the main board as well just to rule out a shorted icon or something. no change

Have not yet checked ESR on caps or diode function beyond obvious shorts with a DMM.

I have read of firmware issues with this series, but there is 0 chance it will stay on long enough to perform an update. i do have several eeprom programmers of various type that i can use to flash the chip, but i didn't want to go that deep into it yet on the chance that i missing something already known.

any ideas?

[tvtimmy]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Does the connector look like this?

[budm]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Another poor quality connector failure similar to this bulletin.

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

yes it looks like that. Not quite as bad though.

For what it is worth i took the wire in question (the browned 5v) and soldered it directly and confirmed a nearly 0ohm end to end. No change.

I don't mind soldering all wires directly if it will help.

Does it make sense that i lose all power rails when this happens? The timing is completely consistent as well. within 20 seconds of hitting power button it will do this.

Do we know why this is actually happen? Some kind of current sensing safety shutdown or something?

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Just an update. I soldered both 5v wires and confirmed nearly ohm connection. Upon further investigation, i do not actually lose 5v standby voltage.

It truly seems like its working electronically like it is supposed to but for some reason the shutdown signal is being asserted after 20 seconds. I have unplugged power button after hitting it to rule out an issue with the keyboard. no change.

If watch the transistor on the main board that controls the PS_on signal, i can watch it open/close as i am experiencing the power off. That is to say, it does not seem like an abrupt power loss, but rathe a legitimate state change on the PS_on signal, and then the PSU responds accordingly.

What is the PS_on expecting to see when on vs off? Is it just a high/low? Im wondering if i can control it manually for the moment an take the mainboard signaling out of the equation.


I have noticed that their are Ebay and other sellers offering a repair service for this main board, they describe my issue almost exactly. Does anyone know what underlying issue they are fixing?

https://www.nickstvs.com/store/p1344/BN94-06124Q

[budwich]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

unplug tcon to panel cables (one at a time) and see if it changes anything.

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

I actually unplugged the entire tcon board as an initial trouble shooting step. Is that not sufficient? I can certainly unplug from the panel as well, but it does require some additional disassembly on this one.

[budwich]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

I guess I didn't read "that" (unplug of the tcon) in your description.... but it could be that the configuration of this tv is "integrated main / tcon".... don't know as you have provided no pictures of the layout. Depending of the design / layout, disconnecting certain portions may help determine the source of your issue.

[budm]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

If the PS-ON line is the only one that toggle LOW after 20 seconds, then you can do the experiment by disconnect that PS-ON wire going to the power supply board, I believe that the power supply board has pull-up resistor to keep the PS-ON high for field service troubleshooting and see if the TV will function without shutting down unless it has more than just bad PS-ON command problem or the main board gets an error signals from some where so it goes into shutdown.
I do not know if this power supply board has pull-up resistors for all the command signals or not, if it does then if you remove the cable between the power supply and the main board and then apply the AC then you should see the backlights come on and stay on as long as the board has incoming AC.

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Yes with the cable disconnected the main board, the power supply will light the backlight forever

Connecting the cable will immediately shut everything off. Well everything except 5v SB

Hitting the power button will light the backlight, turn on the 5V, 12v, and other signals. 20 seconds later, back to only 5V standby present.

[tvtimmy]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

The mainboard is bad. More bad news, none on ebay, only repair service, for$175!!!!!

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Yeah ha i noticed that as well. I hate to scrap the thing if a repair is possible. Obviously it is if they are offering a repair service, but i have a feeling the only way I'm going to find out is to have the repair done and look for what was physically changed on the board. ugg.

In further troubleshooting i took the EEPROM off and read it. Although i can't directly translate it to anything meaningful, there is appropriate strings sprinkled throughout. Part number, date, etc. Problem is exactly the same even with the eeprom completely removed from the board. EEPROM has correct voltages on it in circuit.

Is there any kind of documentation available as to what the startup procedure may be?

Schematic of PSU and Mainboard? If i can get this figured out i am happy to share the secret, ha

[tvtimmy]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

I hold on to high-end tvs for about a year in hopes I come across another with a busted screen. To date, I have only fixed 9 of the good ones I stored in shrinkwrap in the shed. All of craigslist.com is a good source to find doner tvs all over the usa.

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Well I've got some suspects to look into tomorrow
Parts list towards the bottom
https://cdn.badcaps-static.com/pdfs/...7a51209e28.pdf

Quite a few ICs that may possibly be at fault. If anyone sees anything on the list that jumps out to them as problematic, please let me know.

[budwich]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

power supervisor... :-)

Have you tried entering the service mode to see if it stays on?

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Not sure how to get into service mode on this one. Don't have a remote, and the input is the newerish style control where its almost like a DPad. As well, i only have 16 seconds or so from power button push to do anything.

I was told that this was picked from the trash, and then worked for fine about 2 months before doing this. That screams bad connection/solder joint to me.

Based on the firmware file it looks like this runs something similar to a set top box style linux, so maybe i can hook into a UART somewhere and get some kind of debug info.

This feels like a rabbit hole to hell, but i really don't want to get beat by something apparently fixable. Well tomorrow is a new day i suppose.

[budm]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

So the question is: Is PS-ON the only signal that goes LOW after 20 seconds but the BL-ON signal still staying HIGH?

[itelite]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

Well, the board is definitely holding down backlight enable. 0ohm to ground at times, 5ohm to ground at times. would think a legit high signal would be in Kohms at least (agree?)

With that wire removed and ps on removed i get some wacky pattern on the screen. Not sure on sound yet.

Backlight is massively flickering suggesting that the PWM is not working correctly either. Im now hopeful that there is a closed diode or cap somewhere on mainboard causing the holding down of the backlight. I suppose its time to trace from blu_on backwards.

Image remains a mystery. Should be attached.

[budm]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

The pictures should be normal if the only problem you have are the control signals.

[budwich]

Re: Samsung un65es8000fxza turns off after 15-20 seconds

power supervisor ... :-)