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Televisions made by the Chinese multinational electronics company, TCL.

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TCL Roku 65" Black screen, no back light, audio and picture ok.

I have a TCL Roku TV that has a black screen. The back light will sometimes flicker and show the screen but there is no back light. Since all the LEDs light up whey it does flicker, i decided to throw a new LED driver in thinking that may be the problem.

The LED driver did not fix the problem. The only other board i can find even attached to the LED driver is the power supply board. I'm reluctant to buy one however because the power supply seems to be functioning perfectly despite the LED driver now illuminating the picture. Could the main board be bad? Finding a schematic online is next to impossible, has anyone else had this issue?

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@oldturkey03 I replaced the LED driver board. The way it looks like it is wired, has two ribbon cables coming off the Power Supply board. One goes to the main board, the other to the LED driver board. I can't tell how the Main Board talks to the LED driver board since the main board does not appear to be directly connected. I'm just not sure how to proceed here without a schematic diagram or principles of operation how everything is supposed to work. [image|2446631]

[image|2446632]

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@sailor_dan not quite sure about the replaced the LED driver (IC) on the board or if you replaced the driver board. The main board is only responsible for telling the power board to tell on the backlight. Check the voltages going to the LED drivers with a voltmeter. you can also continue to measure it when the light is off. Let us know what voltages you get (set your meter high (~300VDC). It is possible that this is a LED backlight array error so if you maintain the voltages you know to check the backlight strips (The LED’s may still be okay just heating up and turning off). Post pictures of all of your boards with your QUESTION so that we can see what boards you are working with since schematics are impossible to get.

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@sailor_dan I despise not having a schematic but this is what we have to deal with. Anyhow. The LED driver board gets its signal from the main board. It is the main board that tells the power board to turn on and the LED Drive board to turn on as well. Measure the voltage on CN1 of the LED driver board. There should be legend on what voltage you are expecting. BL-On is the one that might be of interest as well. I would see if you have something like 4V-5V on that. It is this that turns your backlight on. Sometimes and I am just saying, adding a 4V-5V cable on that point will turn on the backlight if it is a signal issue. See if it gets that. After that measure the voltages on CN 2. Those will be VDC and with a 65 inch panel I'd be looking at around +300V so set your meter high enough. Going by your description and having worked on a few TCL TV's my prime suspects for your TV are failed LED backlight strips. It's a PITA to fix but just because of the large size. Proper prep and some help lifting etc. will prevent the panel from flexing to much if you have to replace the strips

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@oldturkey03 does the main board communicate with the LED driver through the power supply board? That would make sense since I fail to see how else they would communicate with each other. Really hoping it's not an LED strip. ? There should be a resistance value for the LED strips, but checking they are all getting voltage first is probably a good starting point. Hopefully I can return the LED driver ?it really is a PITA not having a schematic.

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@sailor_dan looks like your model uses 12 LED strips with 7 lights each. you got 3 power lines going of your LED driver board. So your LED backlight strips are probable connected in a Series - Parallel Circuit. Will have to see what the output is. Again you can also try to add some voltage to the BL_ ON connection and see if that get's your back lights to fire up. No more than 5V please ;-) start low and go up to 5V.

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@oldturkey03 So I read out the voltage in VDC using my Fluke at CN1. PDIM- 2.28, ADIM- 3.33, BL ON- 3.33, 12V- 12.27, All GNDs 0, NC- 0.02, All VIN+- 179.6 +/- .2

I'm about 90% sure I'm not getting the correct voltage to the LED driver.

What do you think? I'm figuring out how to connect to the LED strips to check resistance values before applying voltage.

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Bl_ON looks right at the 3.3V . That is the voltage on your power board I assume. (or on the LED driver board?))The only way to measure the resistance is on the cable unless you get to the back lights trips by taking the panel apart.

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