Samsung UN65RU8000FXZA Led Driver Board

[Hink85]

Hi All,

I picked up a Samsung UN65RU8000FXZA 4k Smart TV a few weeks ago, in hopes I could repair it and get it working. It was purchased in Nov 2019, Samsung already replaced this tv by the original purchaser.

I have eliminated the main board and power supply, and back lights are working. It was cycling on and off when i got it, I disconnected ribbon cables until I pinpointed it down to an LED driver board, and with the suspect board or ribbon cable section, 3/4 of the TV will now stay on and it no longer cycles on and off. I haven't found any shorted capacitors on the board. I did find a few threads that said capacitors shorted can be a common issue on the 8000 and 9000 series samsungs.

I have eliminated power board and main boards by using shop jimmy replacements previously, and measured my 13Vs and 3.3V outputs on the power supply connected to the main board and disconnected as well.
Some of the 3.3 voltages drop out with all the LED driver boards connected, obviously causing the on off cycle. This stops with a small ribbon cable 69.75T11.T02 (jumper) removed.

The main board Number: BN94-14163D
Power Board Number: BN44-00932M
LED Driver Board Number: BN96-48077A (4 boards)

I'd primarily appreciate any info or tips for troubleshooting the other chips on the board. The driver board has a part labelled 6514P and a uS5506P chip that I haven't really been able to identify. It would also be great if I could see what the capacitors values should be so I can check they measure what they should. I have also seen threads with people cutting or lifting the ribbon cables and successfully getting the section of the panel back working. I will get pictures uploaded as soon as I can.

Thanks in advance! Let me know if I can get any more info.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Attached pics, if this is a component level repair, I would be comfortable doing so, I just don't have access to a service manual on this tv. I do have a rework station, and a weller analog temp controlled soldering iron, and many years experience building tube amps, and repairing amplifiers. I also know my way around mouser and other sites on ordering parts if I can find what these parts are. If I eliminate the parts and it is a ribbon cable issue or panel, then I may be willing to try lifting the tabs.

[diif]

Re: Samsung UN65RU8000FXZA Led Driver Board

6514P is a diode used for ESD protection.
Check the resistance of the capacitors, under 100 ohms and it's probably shorted.

[neilc6]

Re: Samsung UN65RU8000FXZA Led Driver Board

Looks like a bad panel. Did you remove a side tab already or was it from the top? If it was from the top, the panel is done. Could be shorted chip caps on the panel boards.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

I did perform continuity, but I'll double check the resistance Of the caps when I get home. Does anyone know how I'd find a data sheet on these diodes so I can know which legs to measure for anode and cathode and check to make sure these aren't shorted as well? I didn't have any luck searching online based off the 6514P markings. I haven't tried lifting any tabs at all as of now, there are 3 separate tabs on the Driver board that shuts the tv off. I would much rather find a shorted cap, but I didn't consider ones as high as 100 ohms. I don't know if that may be high enough my meter didn't beep and I just overlooked it.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

The tabs I see were all located at the bottom directly tied to the board, unless there are more on this particular model under the outer frame? I haven’t removed the frame to see either, I thought it was just the 3 tabs going to the board.

[neilc6]

Re: Samsung UN65RU8000FXZA Led Driver Board

So you removed the interconnect flex between boards to disconnect the far left side to get the tv to turn on? That points to a possible short on that side of the panel. That model doesnt have a tcon so your only hope is a shorted cap. If not, you can try cutting the last flex going to the panel a few traces at a time from the outside edge.

Also your terminology is incorrect. Those aren't LED driver boards and have nothing to do with LEDs. I call them panel boards and have seen them referred to as scan boards. They are considered part of the panel and you wont find schematics for them in any service manual.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Okay, I struggled trying to figure what exactly these boards were called. You are correct I removed the flexible interconnect between the two left side panel boards. I will triple check my caps, and if that doesn’t have any luck, I will resort to cutting or lifting the ribbons on the outer edge.

Thanks for the time and input!

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Update, I remeasured my caps in circuit. I did find 2 caps that were smaller than a 1206 package, measured approx 1mm or 1.5mm by 0.6mm. One of the caps measured 0.4 ohms in circuit. I removed the two capacitors and re-measured them out of circuit and was reading in the M ohms. One was 1uF, but I haven't identified the package just yet, and these are small enough I had a really difficult time keeping from losing them. I actually did lose 1, but I will reference the other panel boards with the same chip to see if I can figure what the other cap value may have been, if I don't find it. I had written down some of the values on the back of the tv (in circuit measurements) but will do more testing when I get time.

Any recommendations on an assortment of panel board caps to stock would be appreciated. I was reading approx 1uF, 10uF, 15uF and maybe 30uF on some of these surface mount caps. I already have a pretty big order from mouser lined up for amplifier parts, but I'm definitely adding some of these before I place my order.

** looking through my Surface Mount book - might be the 1005 (1.0mm X .5mm) package or 0402 (1.016mm X 0.508mm)

I will double check these in inch and metric to get it exact

[budm]

Re: Samsung UN65RU8000FXZA Led Driver Board

Sp the suspect cap shows 0.4 Ohms in circuit , but shows M Ohms off the board.
Do you get 0.4 Ohms if you measure the solder pads of the removed cap?
Attach good clear pictures of where the suspect bad cap is.

[eagle00799]

Re: Samsung UN65RU8000FXZA Led Driver Board

Sorry I didn't mean to post this here.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Yes budm, was reading M ohms resistance after removing the caps I Initially suspected. I measured both sets of pads at 36k with the caps removed. I rechecked the other caps and now have a smaller cap showing 10 ohms. These caps were all a common point on one side, maybe the possible other bad cap was masked by the two I thought were suspect, will try to get better pics, but can be tough to get a good focus on my phone, may see if I can get my camera out tonight and get better pics. Otherwise, the cap now testing bad in circuit was not previously less than 100 ohms with the other 2 caps in circuit.

[budm]

Re: Samsung UN65RU8000FXZA Led Driver Board

Yes budm, was reading higher resistance after removing the caps I suspected. I measured both sets of pads at 36k with the caps removed. I rechecked the other caps and now have a smaller cap showing 10 ohms. These caps were all a common point on one side, maybe the possible other bad cap was masked by the two I thought were suspect, will try to get better pics, but can be tough to get a good focus on my phone, may see if I can get my camera out tonight and get better pics. Otherwise, the cap now testing bad in circuit was not previously less than 100 ohms with the other 2 caps in circuit.

I am confused, when the suspected cap was in place it was showing 0.4 Ohms, so you removed the cap and check the resistance of that removed cap and it shows in Mega Ohm mode, and now you are saying the empty pads of the removed cap no longer shows 0.4 Ohms?
Most of the time they will put bunch of caps in parallel so it is not easy to find out which cap is shorted out or if the load is shorted, you will just to remove the suspected cap one at a time until the shorts/low resistance reading goes away.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Sorry I may have made it confusing. Initially I had 2 capacitors in circuit that were showing less than 100 ohms, I removed them and tested them out of circuit and my voltmeter was measuring in the M ohms on the two capacitors I removed (testing out of circuit). With those two resistors still removed from the board, I remeasured the existing capacitors on the board, and am now seeing a different capacitor measuring 10 ohms. I have not yet removed it to measure it out of circuit.

[budm]

Re: Samsung UN65RU8000FXZA Led Driver Board

Sorry I may have made it confusing. Initially I had 2 capacitors in circuit that were showing less than 100 ohms, I removed them and tested them out of circuit and my voltmeter was measuring in the M ohms on the two capacitors I removed (testing out of circuit). With those two resistors still removed from the board, I remeasured the existing capacitors on the board, and am now seeing a different capacitor measuring 10 ohms. I have not yet removed it to measure it out of circuit.

OK, I see.
Just keep on probing, you are gaining knowledge so really nothing to lose.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Pic of caps removed and now reading another cap circled in yellow testing at 10 ohms in circuit

[neilc6]

Re: Samsung UN65RU8000FXZA Led Driver Board

Those caps are usually for decoupling/noise filtering on the power rail so there will multiple ones all in parallel.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

I pulled off the cap I had circled in yellow and I am reading 10 ohms across the pads with that cap removed, saying this cap is difficult to measure out of circuit is an understatement. I measured .44mm by .16mm with my caliper for size but I can’t get an ohm reading on it out of circuit, and read 100nf on capacitance.

[Hink85]

Re: Samsung UN65RU8000FXZA Led Driver Board

Just a follow-up... I am in the process or getting a few tweezer handle solder irons, and I picked up a few large magnifying glasses. I've went through mouser and added a bunch of 0603 / 0402 / 0201 capacitors in different voltage ratings and capacitance values. I want to get the tweezers and pull some caps off and do a few more measurements on component values before I order, just to get an idea on part values (maybe off the boards with no issues, but not sure if I want to risk heating the components up). Voltages I measured on the board are 1.8V and 0.4V on the 0201 package, 6.4V and 8.3V on the 0402 size package, and 16.3V on the largest 0603 package. Will update when I get my solder irons in and get time to pull caps off, and order new parts.

*** Cap values I am trying to add are 0.01uF / 0.1uF / 1uF / 10uF and a few values in between (mostly trying to stick to the highest voltage rating I can get 16 to 25V) If do de-rate the capacitors I would need 35V for the 0603. I've read some people use 10V rated cap for a 5V supply or 25V rated cap for a 10V supply; either way, I want to get the highest rating for prolonged life and buy some in bulk for future possible failures.

[peterkos2]

Re: Samsung UN65RU8000FXZA Led Driver Board

Good day. Did you fix this problem?. I have something similar on the Samsung UE50RU7092 TV.
Thank you for your response