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Samsung UN65JU7500F, Clicking, No Display, Here's What I've done...

Hey All,

Have been lurking this forum after a TV (listed in the title) came into my possession because the previous owner did not want to deal with it. I was originally going to buy if off of them.

During the testing ( I wanted him to verify it was working before purchase), everything was going good, until he decided to plug it into a very old and not likely protected power strip. The screen went blank when he did this, it had the constant relay clicking, with the red standby light flashing 8x during the cycle. It just repeated and sounded like a power cycle.

He offered to give me the TV for free because he didn't want to deal with it.

After reading a bunch of threads on here and performing test, I bought a new power supply and installed it. The problem persisted. I took some voltage readings at the power supply and all were normal.

Here is a breakdown of what's happening now:

The TV is not powering on, as I mentioned it's power "cycling". Ie relay clicking but no image.


Backlights work when connected directly to power so the LED's are functioning.

With the TCON and Main Board disconnected from power supply, no power supply relay clicking and LED Backlights come on no issue when the TV is plugged in. No red standby LED because main board is not connected

With the TCON connected to the power supply and the Main Board disconnected from power supply (but connected to the TCON), no power supply relay clicking, but I get no backlights or screen image. No red LED standby light flashing either (bottom right of the TV frame)

With TCON and Main Board connected to power supply, power supply relay clicks in a repeatable cycle like it's trying to power on and off, but there is no backlights or no screen image. Red standby LED flashes 8x in a cycle with the relay on/off clicking.

I have the old and a new power supply, both are good as they power on the backlight LED's when the TCON and main boards are disconnected. I lose backlight LED's when either the TCON or Mainboard are plugged into the power supply.

I know the main test is to disconnect just the main board from the power supply and if the backlights come on, then it's the main board usually. But when I disconnect the main board (but leave it connected to the TCON), I don't get backlight display and the clicking/power cycle stops.

I have a TCON board coming (new) because it's a $10 board vs $100 for the main board, but I'm wondering everyone's thoughts on what it could be?

My issue differs from most because it takes me disconnecting the TCON AND main board to get LED backlights. FWIW, all the LED backlights work. I can see them through the back screw holes and I can see on the screen as well.

Thanks in advance!

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For anyone that comes back and reads this thread, it ended up being a bad main board. Once the main board was swapped out, all was good again. It seems that there are many different combinations of symptoms so this one happened to be the main board that solved it for this model. Appreciate all of @oldturkey03 's help with this

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@krashdh your T-con board and your main board sort of need each other. This does sound more like a main board issue. You should actually go ahead and measure the voltages on the connector between the power board and the main board and let us know what you get. Also, on the T-con board, usually where the ribbon cable from the main board connects to, should be a fuse. Labelled as F1 or close to the like F1000 etc. Measure the voltage on that. You can also post some good pictures of your boards with your question. That way we can see what you see Edit your QUESTION and use Voeg afbeeldingen toe aan een bestaande vraag this guide

Oh and just to clarify, disconnecting the main board from the power board and the backlight turning on, is only a test for the power board. If they do come on, it's a good power board bad main board :-)

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@oldturkey03, I was hoping you would chime in:)

I've added an image of the back of the TV to clarify a bit better.

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These comments are odd, I can't add a long enough message, so @oldturkey03, I'm going to break this up.

I've labeled all the boards even though you know what's what.

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@oldturkey03

Part 1:

As seen in the image, all the boards are connected. When I plug in the green arrow, there's no image, no backlight, constant cyclical clicking of the relay (purple box), and the standby LED blinks in the pattern.

If I unplug the mainboard from the power supply (red circle) the relay (purple box) stops it's cyclical clicking and there is no standby LED, but I also have no backlight LEDs.

Now, if I go ahead and unplug the T-Con board (blue circle), my backlight LED's are in full array and on. No clicking though because the relay is turned on.

As soon as either of the blue or red circled plugs from either board are plugged back into the power supply, I lose backlight. The only difference is I get the relay clicking/cycling when the main is connected.

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Part 2:

As far as voltages...I was borrowing a multimeter when I last checked. The multimeter I was borrowing had nice tiny leads so it was easy for me to read the voltages on the pin. My vehicle multimeter that I have, the pins are not as fine on the leads and I worry I will potentially arc (would be my fault, fat fingers). I'm trying to avoid doing this on my new power supply. The power supply I purchased was NIB.

I can likely get away with checking that fuse...it's the one right next to the open black female plug on the tcon board (to the right). I assume I can just ground on the chassis of the tv and touch the pos. lead to one of the ends of the fuse? Also, when I do that, should I have everything (all the boards) connected and the TV power cord plugged in (ie blue and red circle, and green arrow are all plugged into their corresponding connectors)?

Thanks a ton in advance, I have people telling me it's my display and I'm not sure how it would be a display issue causing this

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@krashdh no worries about the meter. I can see where in your case you need to unplug both boards. This one gets power etc right from the PSU whereas other models, the T-con gets power from the PUS via the main board. The clicking on the power board is usually caused by it trying to drive the main board circuitry to the rest of the peripherals. So I don't think we have to worry about it for now until we find a replacement. You are playing it smart. Always start with the least expensive board. In absence of schematics etc. it is the right thing to do.

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I am a Samsung Authorized Service Center. In this case you either have a bad main board or the the cables are bad. Need to replace cables along with the boards. Sometimes the cables can go bad also. With the back lights coming on when the main board is disconnected I would lean towards the cables since you have already replaced the main board. However you may gotten a bad main board.

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@n23norris, it turned out to be the main board. Cables were all fine

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krashDH zal eeuwig dankbaar zijn.
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