Samsung UE55F6800SB

[ronhayes]

Re: Samsung UE55F6800SB

This is the item number 202417694006
I have gone ahead and ordered it as it is a new board.

[ducky29]

Re: Samsung UE55F6800SB

Let me know if it works. Good luck!

[ronhayes]

Re: Samsung UE55F6800SB

Hi All
I finally received the main board today and just installed it and would you believe it the TV is still switching it's self off/on ?

Any more input on this would help !!

So far i have removed the connection from the power board and checked connections on main board and p/s board for any burns and both ends of cable non found .

I have removed power connection from power board and backlights come on and stay on .

There are three more connections on the main board one is the ribbon connection to the T-Con and one is to speakers and the other is to the power/remote sensor /whfi.
When the speaker plug pulled set still switches off/on and when put back and power/remote whfi plug pulled set still switches off/on then put back and when the T-Con ribbon pulled and set switched on the back lights come on but no picture and they stay on. Now i am assuming the T-Con board is at fault but when the ribbon is connected it displays a good picture for the short on/off cycles.

Has any one had this kind of issue ?

[budwich]

Re: Samsung UE55F6800SB

how many tcon to panel cables are there. can you provide a picture of the "backside" showing how things are connected. Your tests previously appear to point at the main... maybe you got a bad main.

Anyways, IF there is more than one tcon / panel cable... disconnect only one at a time and wait to see what the results are ... assuming you know how fast it turns off and on in the "normal failure" mode.

[zomi]

Re: Samsung UE55F6800SB

If the tcon was faulty you should not get a picture ?...

Could still be a bad board you have got, regardless of what the seller may say.

What happends if you remove the lcd cables from the tcon
does it power on
try both
then alternate ones.
examine the tcon cable for burn marks
i saw once on a c8000 where it had burnt the cable at the tcon end
but it just clicked and there was no pic.

i really think the tcon is ok but the issue is the cable or the mainboard still

what does the original main board do with the tcon disconnected ?

[ronhayes]

Re: Samsung UE55F6800SB

The replacement board looks new as stated in the add and it was in original package.
When i removed both ribbons to panel and connected ribbon from main board to T-Con the set still switches on/off.
I am not convinced it is the main board?

[ronhayes]

Re: Samsung UE55F6800SB

I have tried the original main board in and when i unplug the ribbon to the T-Con the backlights come on and stay on when the ribbon to the T-Con is re-connected the set switches on/off again ?

[budwich]

Re: Samsung UE55F6800SB

please provide a picture of the back of the set so we can see how things are connected up so there is no misunderstandings.

[ronhayes]

Re: Samsung UE55F6800SB

I have removed each cable going to the panel one at a time same issue set still switching on/off.


Sorry forgot to add pictures.

[budwich]

Re: Samsung UE55F6800SB

:-( thanks, I was hoping you would find something there. Having said that, you saw no difference in the "half picture" being displayed? Also no difference in the time for the set to switch off/on? Further, the "on/off" is just that... its not "on/off/on"... it doesn't come back by itself.

As Budm posted, I would focus on the powering going from the power board and main. You may not see any marking but the connector pins themselves may not be keeping contact at time or possibly a broken wire in the cabling that is heating up and doing the "on/off" thing. You might have to monitor some of the voltages and watch during the on/off cycling.

[ronhayes]

Re: Samsung UE55F6800SB

Yes it is the same when each cable is removed picture one side white screen the other side.
But it is still going off/on at the same time scale it keeps going off, then comes on, on it's own and keeps going off then on until you disconnect the power.

I see what you are saying about the power connection from the power board !! but surely wouldn't it still do this with the T-Con board disconnected if it was Main board or p/s board ?

[budwich]

Re: Samsung UE55F6800SB

you are probably right..... but maybe not. Of course, I know nothing about the operating system in terms of what it monitors but I give you this scenario that perhaps the main board monitors a condition from the tcon... let's say 12v... on some sets that is provided directly from the power board while on others it is switched thru the main... design dependent... if the 12v disappears the main may go into error and shut down... once down, perhaps the 12v comes back and the system starts up again.... but when the tcon is disconnected, maybe there is no "initial handshake" with the tcon to main and thus the main no longer monitors the 12v line as the system path is more of a "limp mode" which keeps power on the backlighting. Just a "dreamed up scenario" based on no knowledge.... but perhaps possible.

[ronhayes]

Re: Samsung UE55F6800SB

What i have tried now is to connect a dvd player via scart connection and unplugged the T-Con ribbon plugged in TV and backlights have come on and the sound has come on have tried turning sound up and down with remote and works ok.

I have also tested the volts on the power connecter on the main board from power board and they all stay steady only time they drop is when the set switches its self off but they return when it powers back up on its own

[budwich]

Re: Samsung UE55F6800SB

:-( well still looks very much like a main board. The last things you need to do is expand you "tested the volts on the power connector". You need to look and measure ALL of the pins on the connector... it will take a bit as some come and go depending on the powering state.

basically, you need to state the label of the pin (tells us what it is), the value at standby, value at power on, and maybe value during the "off" happening... hence it might take a bit. Some of those are control pins.

I see from your pictures that indeed the voltage for tcon is switched thru the main.

[zomi]

Re: Samsung UE55F6800SB

Where are you pulling the tcon cable at

the motherboard end
or at the t con
does it make a difference where you pull it or is it the same ?

[ronhayes]

Re: Samsung UE55F6800SB

Is this where i need to test the volts ?

[zomi]

Re: Samsung UE55F6800SB

yes

[megaraider]

Re: Samsung UE55F6800SB

imo the problem started in the PSU (overcharge spike or over-voltage) and only then it spread out burning the mainboard.
Check the voltages outputs at the PSU. Play special attention to fast decays in voltage power rail levels when the unit goes from OFF to ON.
Also, zooming in on the 1st picture you posted (PSU) a cap immediately caught my attention, has bump in the head, and others might be dry.

[ronhayes]

Re: Samsung UE55F6800SB

It does the same if you pull the T-Con ribbon from main board end or from T-Con end the set stays on but when it is connected the set keeps switching off/on continually you can't even put it in St/by you have to pull the power cable to shut it down. When the T-Con ribbon is removed from either side you can put the set into St/by or bring it out of St/by but you can't do this function when connected.

I have added a more clear picture of the P/S board and i have changed the cap mentioned but on testing when removed it reads ok.

[vinceroger69]

Re: Samsung UE55F6800SB

something on the lcd panel pcb causing a short? or lcd panel failure? have you still got the lcd panel tester you could try using on this set