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TV repeatedly turning off/on (power cycling)

As of now, my after turning on my TV, I can see the backlight turning on for a second or two, then turning off for a second or two, and endlessly repeating this cycle.

Background:

This began to occur a couple days ago when I was playing a game on my Xbox One, which was connected to the TV through my receiver. Mid-cutscene, the picture became darker (but still visible) and then vertical green lines appeared over the image, growing and moving horizontally across the screen. Once I realized this wasn’t some weird-ass cutscene thing, I turned everything off, waited a minute, and turned the receiver back on, which also powered on the TV via CEC, and then the power cycling began, which I eventually narrowed down the the TV behaving as I described above.

I took the back off the TV to see if I could find any obviously bad capacitors, but from what I can tell (I am no expert) they all look pretty good to me.

I was hoping somebody here could give me any advice and/or guidance.

Thanks!

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Update (07/16/2020)

I did some more testing/experimenting/bumbling and determined that the TV will not power cycle when one half of the cable going between the power board and the main board is disconnected (it’s the “northmost” connection on the “east” side of the main board, see picture).

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After realizing this, I reconnected it and then powered on the TV after disconnecting one of the cables coming out of the main board, one by one sequentially. I also tried disconnecting both ribbon (FFC?) cables coming out of the mainboard simultaneously. With each test, the TV still continued to power cycle.

So, I think the problem might be the cable going between the power board and main board. I tried finding it on samsungparts.com, but the only cables listed there are FFC cables, so I’m not sure how to go about getting a replacement.

Thanks in advance for any ideas!

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I tried pulling out and reseating each of the ribbon cables coming out of the main board, but no luck.

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I am having the same issue..did you ever find out the problem?

完成的

I think the cable ended up being a red herring for me. Eventually I found some burnt up resistors on the buffer boards (I think that's what they're called?) at the bottom of the screen. I removed them using a heat gun and some small pliers, which got me a less distorted, but still unusable, picture.

Here are pics of the burnt resistors. They were on the bottom-right and bottom-left boards: https://imgur.com/a/KbcUdc5

The best help I got was on the badcaps.net forums, you might consider making an account and posting there. I just ran out of steam on the whole thing or else I might have soldiered on with those guys.

Sorry I couldn't be more help.

完成的

Reopening this question. I have the exact same thing with my tv. Same TV as yours. No solution.

I replaced all the board's thinking that could solve something, main board power supply all the cables, everything. My TV flickers when no picture is playing, but if the cable box is hooked up, and on, then the tv will act somewhat normal.

Now it's starting to power cycle and flicker the backlight as well. It's all a mess. Any ideas? I'm thinking I might need to replace the backlight but they all seemed to work just fine when I do get a picture.

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@weezyfiggs I recognize that this is old but I would suggest to check one more thing. Disconnect the main board from the power board. Does your screen show the backlight? Does it stay on? If it does not then the issue is your backlight array on the inside of the panel. Let us know what you get. Of course this will only work if you A. still have the TV and B. if you have not yet gotten it fixed. :-)

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Hi @weezyfiggs

Try the following:

Disconnect the power from the TV.

Disconnect the cable between the power board and the mainboard.

Reconnect the power to the TV.

The TV screen backlights should turn on full and stay on. There will be no picture because the mainboard is disconnected.

If the backlights don’t stay on or they blink then there is a problem with the power board or the LED array.

Disconnect the power from the TV and then disconnect the LED power cable from the power board. Reconnect the power to the TV and then check the voltage at the power board’s LED power cable connector. It should measure ~ 250 - 280V DC or maybe even as high as 300V DC If it is not that high or is pulsing it is a power board problem. If it is steady it is a LED array problem.

If the backlights stay on, check the voltages at the power board’s mainboard cable connector and see if they are as per what is marked on the power board near the connector. If they are as marked and also steady then it is a mainboard problem

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Thanks. I did as you instructed and the backlight stayed on, so I tested the pins in the connector, which was labeled 13V. Each of the pins that were labeled 13V tested at 12.74V, so if I follow you correctly, it sounds like I should start looking at the mainboard, but I'm not sure what to look at there. Any guidance would be appreciated.

Thanks!

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Hi @weezyfiggs

Mainboards are harder unless you can find the schematics or service manual for it. You could try searching online for "(insert mainboard 'board number') schematic" and hope that there is one available online. If it is a newer model this is less likely though.

The other possibility is that it is a firmware problem (which is on an eeprom on the mainboard anyway).

Unfortunately it doesn't state on the support page for the TV if it is possible to load the firmware without going through the TV menus, although I did find this procedure for another model which although it shows that you have to use the menus perhaps they may still work when the USB option is loaded

A lot of TV makes including Samsung allow you to load the firmware via USB by downloading and copying the firmware (usually a .bin file but may be different) to the root directory i.e. not a sub folder of a USB flashdrive and then inserting the USB into the TV and turning on the TV. Part of the normal boot up sequence is to look for a USB file with the correct file name and then if there is one there install the file from there and restart the TV. Normally this occurs very early on in the boot process. If the correct file name is not there then it proceeds with the boot up of the TV

I am thinking that if the firmware was corrupted that usually this part of it is safeguarded to allow for a re-install.

As I said it isn't mentioned for your model but you never know. If it does start to load etc, allow some time for it to install and configure etc and also for it to restart i.e. be patient ;-)

-----------------------IMPORTANT--------------------------------

If you decide to try this it is important that you get the correct firmware for the TV as the wrong firmware will brick the TV and the only way to fix it is to replace the eeprom with one that has the correct firmware for the TV or the mainboard. Make sure that the page I linked or the one you need is for the EXACT complete model number of the TV.

-----------------------------------------------------------------------------------------

If you can't find a schematic and IF the firmware doesn't work as described above etc, then you may have to replace the mainboard.

Search online using the TV model number or the mainboard"board number" to get results for suppliers

完成的

Thank you again!

I ordered a replacement mainboard before I saw your reply. It came today and I swapped it out, but I still saw the same issue. My guess is that a different mainboard with the same issue rules out a firmware corruption, though I suppose it's possible that I got a second board that already had the same, or similar, issue (it is a refurb, after all).

In any case, I plugged in the firmware-loaded USB drive and powered on the TV; it seemed to just power-cycle as expected, without taking the opportunity to install firmware from USB, but I let it go a while. I called it off at 15 minutes of no change.

I noticed in one of your links above that there is a way to flag the TV to install from USB at boot, but Samsung's own link for that isn't working. However, I gathered from the link below that I might be able to just create a blank file called SWU_AUTO_FLAG at the drive root - I'll try that next and report back.

Link: https://eu.community.samsung.com/t5/tv/n...

完成的

Well, I just installed the replacement power board, and I'm still experiencing the original issue - to be clear, this is now using a replacement mainboard and a replacement power board simultaneously.

I should also note that, while working on the TV over the past week, I've been using a different outlet and circuit than the one where I originally encountered this issue.

If anyone has any other ideas, I'm all ears!

完成的

Hi, any update for this issue? Fix or no fix?

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Normally, most TVs will power up after a few seconds of turning on power to allow the PSU to stabilize. When the relays activate, if there is a problem with other powered circuitry, as in an abnormal load, it will then shut down and start the power cycle again. Disconnecting a cable would point to the board that has a problem. However, if that board is connected to another circuit the problem might be in that circuit. This follows Brandon’s find of burned resistors off the main board. Replacing the resistors will not solve the problem until the cause of the burn is found. A schematic will tell you what the resistors power, and of course, if the resistors are burned only a schematic will tell you what the value is.

Otherwise, it is replacing parts till you get results, which can become more costly the a new TV.

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