Samsung UE65KS9000 lines and reboot loop

[mrsith]

Hi, yesterday I've got a UE65KS9000 which has some lining on bottom of the screen, and reboots itself every 20 seconds or so. Seems like it gets worse with time, i.e. first boot just the bottom of the screen is wrong, then over time and over restarts it gets worse.

I've tried the cut tape method on both motherboard-to-panel ribbon tapes as well as both U-shaped tapes on the panel. If the panel woke up the lining was always there, so I guess I wasn't lucky enough with taping.

Not really sure how to progress, there are no typical test points on the boards. No idea why one of them is blue. See pics attached. Any ideas what to look for or which pins to block appreciated.

Thanks in advance fir your time and patience

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

I've seen a thread with KS8000, similar built TV.

https://www.badcaps.net/forum/showthread.php?t=72245

Is there any point trying to swap mainboard in my unit or is it definitely, 100% LCD panel board (or t-con which is built in there) related issue? If that's the case, could you please guide me where should I put probes to measure key voltages like VCC etc? Like I said in previous post, I can't see any testpoints, prints on the boards don't guide me well enough.

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

if you're saying you have another mainboard on hand to try, sure give it a try.

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

Well I don't have it, just open to the option of buying/finding it. Wouldn't even ask if I had it :P I'll try to find a broken one to replace everything replaceable.

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

indeed, I thought you would have if you had one, you can try this same as the other one to see if you have any bad caps if you didn't already, your quote there:
Double check the capacitors on these board (on your faulty screen), put diode mode and check each capacitor leg-to-leg, also check each leg against the ground. If your meter doesn't beep it's gonna proba ly show ~030 for shorted caps vs ~600+ healthy ones. Most likely you will find quite a lot of shorted caps, the problem is determining which one of them actually causes it.
In diode mode, just put one probe to one side of capacitor and another one to the other side. Or put negative probe on the ground (i.e. chassis), and positive to each leg of the capacitor. One leg should return high value, while the other should be clpse to 0. If both are suspiciously low then its probably.a short there.
Do this with everything connected, but without power cable in.
"

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

Wow, I feel almost wise, being quoted to myself

I'm gonna go ahead and start looking, cannot rule out the main board so I'm gonna check there as well.

Also, I've found this:

https://www.badcaps.net/forum/attach...6&d=1467689646

that's not exactly my model but they're built in similar fashion. Mine fails straight away, but this tells me to test the PSU as well.

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

ok, yes indeed, look for those tell tale brown burn marks on the connector.

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

I have measured every single cap and resistor on the TV panel boards, everything seems okay there. There are a couple of bigger elements I am not entirely sure how to properly test.

Found a service manual for this model. Tried tape method again, covering all CKVx and CKVBx pins, but again no joy. Checked PSU voltages, not sure if I should be reading almost 4v from fail_count. I've been looking around mainboard as well, trying to find anything wrong, but everythink looks and measures okay.

Attached pics of the smd's I'd like to test.

[Diah]

Re: Samsung UE65KS9000 lines and reboot loop

don't spend any penny on this ks9000 & NU / TU shit on Korean Samsung.
its wrong hardware of panel designed.. and who read this and still like to buy Sami..ask for advice before buying. and who owned those series and like it. i would say keep calm you will be victim of it soon.

[Storyteller12]

Re: Samsung UE65KS9000 lines and reboot loop

don't spend any penny on this ks9000 & NU / TU shit on Korean Samsung.
its wrong hardware of panel designed.. and who read this and still like to buy Sami..ask for advice before buying. and who owned those series and like it. i would say keep calm you will be victim of it soon.

I know about the NU and TU series and they are junk. I never had any real problems with the KS series of TVs. Other than the diode pack that goes bad on the buffer boards.

The ks series in my opinion is one of the best TVs Samsung made. Picture quality is pretty good and the design of the tv looks great with the thin bezel.

Just my opinion though

[Storyteller12]

Re: Samsung UE65KS9000 lines and reboot loop

Your problem looks similar to the diode pack I mentioned that goes bad on the buffer board only when most go bad we get no picture at all just lines.

Try putting flux on the resistors and diode pack on the buffer boards then turn the tv on.

See if the flux starts melting faster on one of them. That’s how I find some bad caps or resistors sometimes.

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

Your problem looks similar to the diode pack I mentioned that goes bad on the buffer board only when most go bad we get no picture at all just lines.

Try putting flux on the resistors and diode pack on the buffer boards then turn the tv on.

See if the flux starts melting faster on one of them. That's how I find some bad caps or resistors sometimes.

Will do just that, tried to find something with pistol-type thermometer but think it's not precise enough.

@Diah - fortunately I got this one for free

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

Tried the flux method with no joy. It didn't melt at all, anywhere. Confirned with my fingers, everything is stone cold on the buffer boards.
Any chance this is actually PSU or mainboard issue?

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

unhook cable from powerboard to mainboard, plug in power cord, see if backlights come on and stay on.

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

maybe post some pictures of each board and one of the whole back as to see how everything is connected.

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

Pictures attached. The backlight comes and stays on allright, the rebooting happens only with mainboard connected.
I have also included service manual for this TV, just in case it may help you help me

[nomoresonys]

Re: Samsung UE65KS9000 lines and reboot loop

not sure, maybe something like this will do it: https://www.badcaps.net/forum/showthread.php?t=107445

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

I have actually seen this thread, the thing is - as stated earlier - this TVs panel board doesn't seem to have any testpoints, not sure how to measure/diagnose it and thus where to solder the wire.
What if I'd found the VGH pin using the service manual and measure it from there? Then I could maybe solder the wire directly to that pin on the connector of the panel board. Not really sure which resistor should I desolder to put a wire from there

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

The word 'VGH' doesn't appear in the service manual even once. No pin is labeled this way. Nothing on panel board is labeled like that.

Please see pics attached. There are key voltages marked on the boards (AVDD etc), but they don't seem to be related to any particular point. Where ahoukd I check the voltages then?

Apologies for some flux left on the photos :p

edit: after carefully inspecting linked thread, I see that the VGH won't probably be listed in the manual. Seems like the pinout is the same though, so I'll take a look what pin 84 shows and take it from there. Will post update soon.

[mrsith]

Re: Samsung UE65KS9000 lines and reboot loop

If I calculated the pins right, the VGH voltage shows -0.25v when the TV is on, jumping briefly to ~0.5v while it restarts. Even if I messed up and measured wrong side connector and thus wrong pin (not really possible as used CN number as a reference), the corresponding pin on the other side would be VCCA_1.9V_PW, which still isn't -0.25v.