•• samsung * ku * range troubleshooting information ••

[Hamie]

Ok so a bit of a long winded post but noticed a few posts on various KU models with all with the same fault.

*TV turns on, backlight flashes then back to standby repeats

So I fairly recently acquired a 55" (from memory ue55ku6700) one of these with a cracked screen for free that I intended to use for parts, however upon switching it on it had the above fault. These models do not use a tcon, disconnecting the mainboard and the backlight comes on and all voltages from the PSU are accurate. Disconnection the panel from the mainboard and the fault returned. So I assumed not only does it have a cracked screen but also a bad mainboard.

Never the less I kept the parts,

So a few days ago a friend of a friend calls me to say he has a faulty UE55KU6470 this time the fault is similar to the old as15-f gamma faults, blues were washed out and reds were hazy.

So I decided to unplug half the screen just to see what happened, and surprisingly it doesn't turn on and instead starts boot looping. I disconnect both and again it's looping.

So I put in my previously though faulty mainboard reconnected everything and it powered on fine with perfect image and no gamma fault.

So to summarise, these TVs don't turn on if you disconnect the panel, they loop, if you have a cracked one thats shorted a driver it again won't turn on.

Also if you have one and have already replaced the main board and it's still looping then there's a far higher chance that the panel is shorted rather than the mainboard you've bought being faulty.

Personally If you see someone selling one with a similar fault its probably worth avoiding. If you're fixing one for someone ask if before it failed if there were any vertical lines before it conked out.

Might help someone

[dick_barton]

Re: •• samsung * ku * range troubleshooting information ••

Thanks for the information which may prove valuable to some at a later date.

[freakaftr8]

Re: •• samsung * ku * range troubleshooting information ••

Wow! Very interesting. It must be some overcurrent trip from a underdeveloped circuit from voltages not being delivered to the panel causing stress on the multi PWM circuit.

[retrofix]

Re: •• samsung * ku * range troubleshooting information ••

You can include the KS series because what you describe is EXACTLY what I'm experiencing with my UN49KS8000F. Problem began with a thick black vertical line along the right side of screen. Now it's boot looping with flashing backlight and Samsung badge. I have a new mainboard on the way but I'm not confident that replacing it will bring the set back to life.

What might be causing the panel fault/error? I'm assuming there's a bonded tab where line was that is coming apart but would curing the tab solve the issue or is there likely a shorted chip on the signal board also?

I also see a Winbond memory chip on the signal board that might have become corrupted.

I appreciate your highly informative post.

Thanks

[RJARRRPCGP]

Re: •• samsung * ku * range troubleshooting information ••

Bad COF adhesion is suspected.

[budwich]

Re: •• samsung * ku * range troubleshooting information ••

I would give some form of "tape cutoff" method a try... some how cutting off some of the signals going to the panel ... you might get lucky.

[CuriousJohn]

Re: •• samsung * ku * range troubleshooting information ••

Maybe I wasnt so lucky to find this info before purchasing a spares or repair Samsung 55JU6740 that had symptoms of dead backlight or mobo so perhaps include "JU" as well depending....

Apologies for what might appear thread hijack happy to start a new thread but seems relevant here.

When powering on this TV the Tcon blue led flashes on for a second then goes off i suspect it does this to protect itself. By disconnecting one of the two ribbons from Tcon to panel the tv would start up and backlights come on but still no video not even half a screen worth. These curved sets also have ribbons between the far end tabs so i did the same and still no sign of any video.

With Ref to the photo attached below which shows the far left tab if panel was seen from the front.



I detected a short across what i think is SMD C01 so removed it to find it ok. So i removed the tiny black SMD next to it that is in parallel with the Cap, one side to ground the other side feeds into the panel itself and yes it is S/C off the board. I have no idea what this SMD component is as has no markings i can see and the board suggests it is R06. Similar tiny black SMD components on other tab also measure short but do not cause any Cap to be S/C so suspect it a plain old link but doesnt make sense being in parallel with a cap to ground, not from DC point of view anyway and if its a resistor what value?

So With these two components still removed i decided to power up for a see what and still no sign of video on panel however i can now have both ribbons from Tcon connected and it powers up ok so long as i dont connect the far left tab with the mini ribbon.

I guess this a long winded way of asking what is R06 and should i stop wasting my time trying to fix a bad panel. I need to find a suitable SMD component to replace and put the SMD cap back on to see if miracles happen this Christmas...

[budm]

Re: •• samsung * ku * range troubleshooting information ••

Yes, that is R06.
Look at other section of the board, it may have the same circuit setup so you can verify what that resistor is.

[CuriousJohn]

Re: •• samsung * ku * range troubleshooting information ••

Thanks budm I have put the SMD components back on i checked around no similiar circuit on other driver tabs all similiar smd components appear to be sc so links but no marking on them and no other appears to be connected in parallel with a cap straight to ground. Think I was chasing ghosts anyway as appear to have made an error in my last post.

With both of the far end panel drivers boards connected (A + D) the tv will not power up the tcon flahes its blue led once and powers down, with ether one of them disconnected the tv powers up fine but no video on screen, also noted tcon gets warm like this but not hot and has volts in and out as expected. This tcon was bought cheap but stated known working, the original tcon performs the same.

I begin to possibly accept a bad panel because all passive components on panel driver tabs test ok other than the oddity described in the last post with the smd cap wired in parallel with a link to ground so appears short across it, cant find any other issues leaping forward.

There is a winbond spi flash on one of the panel drivers and a couple of tiny smd packages possibly just resistor packages. That winbond chip has 3.3v embarrassed to say have no idea what a spi flash chip is doing on a panel driver board.

Going to try taping some panel driver connectors off with sellotape when I have more time to see if something can be restored but for now this TV is RIP suspect bad panel.

A service manual for the chasis would do wonders if one is out there?

Heres a photo of the thing...

[CuriousJohn]

Re: •• samsung * ku * range troubleshooting information ••

Can anybody help please this curved samsung tv is still refusing to show video on the panel and has winbond spi chip on one of the four panel drivers which is perplexing me and cant find any info, why would a spi flash chip be there does anybody have any idea? It is a Winbond 25Q64FV and is receiving 3.3v as it should be but no idea if its working or not.

[CuriousJohn]

Re: •• samsung * ku * range troubleshooting information ••

Any one?

The Tcon has its EEPROM and the panel driver has this EEPROM, the cynic in me wants to believe Samsung are coding there panels to the tcons to prevent repair or swop out but I resist there must be a better theory of operation. Why a SPI flash EEPROM on a panel driver!!

[diif]

Re: •• samsung * ku * range troubleshooting information ••

Why not read the SPI flash and find out ?

[CuriousJohn]

Re: •• samsung * ku * range troubleshooting information ••

Im going to man soon as i get time watch this space.

[misterhaus]

Re: •• samsung * ku * range troubleshooting information ••

@CuriousJohn - did you ever figure out this issue?

I've got a UN65KU630D that is similar in that the LED backlights cycle on and off on about 7 second cycle. Backlights stay on constantly if I disconnect the cable between power supply and main board.

If I disconnect a single TCON cable (at main board), then the tv stays off when I plug in power. When I press power button I hear two tones and then the same 7-second backlight cycle.

If I connect both TCON cables, then it turns on immediately after plugging in cord and cycles backlight on similar 7-second cycle.

I've tried checking voltages on edge board and many test points have only very small voltage. Doesn't this tv have VGH/VGL test points? Anyway, my hunch is something turns off during boot up due to a fault.

Not sure if it's panel fault. Not sure which pins to block with cellophane tape.

Any ideas?

Thanks,
Rich

[nomoresonys]

Re: •• samsung * ku * range troubleshooting information ••

Hard to tell but I suspect the mainboard.

[dragometin]

Re: •• samsung * ku * range troubleshooting information ••

I think this can also be applied to the MU6225 series. They also dont have a tcon board.

[howardc64]

Re: •• samsung * ku * range troubleshooting information ••

So to summarise, these TVs don't turn on if you disconnect the panel, they loop, if you have a cracked one thats shorted a driver it again won't turn on.

Ditto!

Have a terribly cracked panel UN55KU6290FXZA. Disconnect either/both panel flex cause TV to boot loop.

TV boot properly laying flat and hear UI sound. But if tilt the screen, will reboot -> boot loop. Likely from the terribly cracked panel (many crack lines and impact points, looks like someone beat up the LCD haha)

Will harvest boards including main (likely good but can't prove it)