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Presumed dead backlight, but TV does get some flickers on startup. Could the problem be elsewhere?


Called by my mom when her TCL TV went black. Pretty quickly found it to be a dead backlight.




Noticed on a hard power cycle that the screen can briefly flicker on during startup.


I'm not a display guy, so before I made any promises about just replacing the backlight I wanted to check here to be sure it was the issue. Figured backlight being dead or alive was binary, so the flickers of life got me worried it could be something else, like maybe some wiring that's right on the edge, IDK. The last thing I want to do is get her thinking I'll fix it only to find out it's some deeper component too far out of my wheelhouse. She's already worried about having to delay the new carpet for the 50th time.


Situation, with a bunch of info since I don't know what is or isn't relevant:


1) Only occurs on hard power cycle, after plug pulling.

2) Only occurs during the startup, while the TCL/Roku screen is up. Ceases once the menu has loaded.

3) Occurrence of flashes can be replicated, nature cannot.

4) Most times it has flashed on was three, least was two. Not effected by time off or brightness setting.

5) Timing of flashes is not consistent.

6) Duration of flashes is not consistent, never more than about 3/4 of a second, some almost a blink.

7) Flashes rarely reoccur within a second of each other. More typically, three to eight seconds separate them.


If this is something that can be diagnosed by someone more knowledgeable about displays, it would be appreciated. I'd rather be too hesitant to be right, than be too eager to be wrong.


Many thanks for any who take their time for this.

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Sometimes failures are temperature related.  Something could be in a "failure" state when it's cold, but as it gets heated up, it could start working. 


For example LEDs are made from  very small silicon die which is soldered to a base material and there's one or two bonding wires connecting the other end of the die to the terminals (pins) of the led) 

See picture below, a RGB led has all 3 silicon dies (one for each color) "glued" to a base material, and then there's 2 bonding wires on each die, one for each end of the led. 


In some cases, one of those bonding wires can come loose at one end and not make good contact. Or not even loose, could be bad soldering joint. The backlight circuit detects that the chain of leds which has this faulty color consumes less power and stops backlight from working to protect the other leds. But as the backlight flashes on and off,  it's possible for the led to get heated enough from the other colors so that the gold bonding wire stretches by a very small amount and now touches the terminal and makes a connection, and all three colors work and now the backlight circuit sees good power consumption and keeps working.




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