I have a JVC LT-42E910 LED/LCD TV. The unit powers on fine. The screen displays the please wait box and then shows snow if it's on antenna but after about 5 seconds the screen goes dark. I replaced the FRC board thinking that there wasn't any image on the display, then to figure out that everything works, sound and display it's just the backlight is out. The picture can be seen if you shine a flashlight into the screen. Which board on this model controls the backlight or what can I check? I have searched for a service manual with no luck. Thanks for any help.
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Re: JVC LT-42E910 Led/Lcd backlight issues
Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem -
Re: JVC LT-42E910 Led/Lcd backlight issues
My guess is that you have a bad LED in the backlight.Comment
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Re: JVC LT-42E910 Led/Lcd backlight issues
Ok, I have attached a picture of the back of the television. I am still stumped by what could be wrong with this tv. Ive tried changing out the power supply board with a cheap used one I purchased off ebay. That made no difference. I don't know how relevant it is but the backlight only will turn on for the short 5 seconds after the tv is first plugged in and cycled on. If I push power off and put the tv in standby and then power it back on, the indicator led turns blue but now it doesn't attempt to even light the backlight at all. I after watching some youtube videos agreed with the previous post and thought I had bad led(s). I tore the entire tv apart, exposing the leds, it does not have led strips like I had seen in the youtube videos but instead has four thin circuit boards with tons of LED's which are attached to aluminum bars running across the top and bottom (two boards on top and two on bottom) I hooked the power switch up and plugged it in and observed the leds, when they turn on, all of them are lit with the same intensity which is very bright and none of them are out or dim. I tested voltage at the backlight inverter board and it has a constant 24V regardless of whether the backlights are on or when they go off. Could one of the other boards be bad? What board tells the backlight to turn on? Any thoughts or ideas are greatly appreciated!Attached FilesComment
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Re: JVC LT-42E910 Led/Lcd backlight issues
Maybe look at the BLon (back light on) signal. Comes from the main board to the PSU. Problem is, that I can't see any pin outs so we would know what is what. Maybe you can measure all pins on the PSU with the TV off, then redo everything again with the TV on. Gonna be not that easy.Comment
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Re: JVC LT-42E910 Led/Lcd backlight issues
Ok, Ive attached another pic showing a closeup of the inverter board. With the TV off, BLON shows 0V DC, when the tv is switched on it shows 3.15V DC and remains unchanged regardless of whether the backlight is on or off. When the TV is switched off and put into standby the BLON voltage drops back to 0. Any thoughts or suggestions? I'm really confused by this and ive tried a different backlight inverter board but still the same results.Attached FilesComment
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Re: JVC LT-42E910 Led/Lcd backlight issues
Wow a real JVC looks decent build quality lol you probably need a new firmware flash or try to do a factory reset while shining a torch on the screen
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Re: JVC LT-42E910 Led/Lcd backlight issues
Since you get BLon to the inverter board and the LED's are good, the problem should be the inverter board itself.
Could you upload a nice straight shot, high quality picture, so we can see the board better?Comment
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Re: JVC LT-42E910 Led/Lcd backlight issues
How about the Dimming control signals E_PWM, and I_PWM? Do they go away when the Backlights cut out?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: JVC LT-42E910 Led/Lcd backlight issues
Ok, when the TV is powered on I-PWM shows 3.29V when the backlight is off, when the backlight illuminates it stays basically the same at 3.30V. E-PWM shows 0V when the TV is powered on until the backlight illuminates which then it only shows .16V until the backlight turns off then it drops back to 0V.Attached FilesComment
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Hello,
YouTube video of the problem encountered: https://youtube.com/shorts/q7TLNv36LUo
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