Sharp Roku LC-55LBU591U Back light is on but no picture. - RESOLVED
Hello. I have a Sharp Roku LC-55LBU591U TV that has no picture but seems to have all other functions. When using the remote I can hear the normal sounds as I’m making selections but the screen is simply black with a back light. I unplugged the ribbon cable to the t-con and half of the screen went white.
I tried to test voltages at the t-con board but I’m not really sure what most of the test points should be reading. I get a decreasing range of voltages at the various ribbon test points.
I will post pictures momentarily.
Any help is appreciated.
Update (07/14/2020)
Pictures:
Update (07/15/2020)
Main board:
Update (07/24/2020)
I am proud to report that the replacement main board solves the problem. Full functionality and picture has been restored to the tv.
thanks so much for the help
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7 comentarios
Hi @chillin014 ,
Just verifying the following:
No video at all when using different inputs, input types e.g. coax, HDMI, Component video, input cables, signal sources e.g dvd player and also no TV menu screen?
Audio works though?
- de jayeff
@chillin014 ... please test the 5a 32v fuse on the tcon board. (power on state with backlight lit) test both side and list voltage here. also, test vdd4 and vdd12 and list the voltage here. if no voltage is present, the likely culprit is the main board. post a pic of your main board so we can see whats going on there as well.
- de jostewcrew
@jostewcrew Fuse seems to be good. 12 V coming through it. I could not find VDD4 or VDD12 for the life of me. Searched all over the board. Can you point me in the correct vicinity? I've added a picture of the main board to my original post.
@jayeff Audio works fine. Admittedly I haven't tested the inputs because I have no idea how to cycle through them. It's a roku remote and no designated input button. I can hear the sounds when I use the remote like its searching through the menu.
- de Christopher Hill
@chillin014 .. if looking at the main ic on the tcon, to the right youll see a smaller ic. vdd4 is directly above this as a test point. vdd12 is the ic immediately left and the test point is above this.
- de jostewcrew
@jostewcrew I found vdd12 but I couldn't find vdd4, do you mean VCOM?
Vdd12 - 6.36 V
VCOM - 1.18 V
- de Christopher Hill
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