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HELP me repair a HP SL4282N MediaSmart 42” LCD HDTV

tmink

May 27, 2021
2
Joined
May 27, 2021
Messages
2
Hello all! I am brand new to electronics repair, but I am a hard worker and a fast learner.

My TV screen stopped working a few days ago, shortly after a power outage in an older building in old Denver, but the power light can still be toggled on and off (yellow = on, blue = off). The TV is a freebie, “old” hand-me down, and I’ve purchased another for actual TV entertainment. However, I am looking to turn this TV into an extra monitor that I can connect to my computer via HDMI or VGA.

I’ve opened the TV and everything looks “normal” (to my very untrained eye), except for half of the power supply board (mostly the thick metal “scaffold”, possibly called the heatsink??) is coated in a white dust.

Can anyone help me/guide me toward the feasibility of what I’m looking to accomplish? Any ideas of what went wrong or how to diagnose?I’m happy to provide pictures of any components needed to help troubleshoot. Thanks so much in advance!

Best regards,
Taylor
 

Bluejets

Oct 5, 2014
6,990
Joined
Oct 5, 2014
Messages
6,990
Many LCD screen faults can be tracked down to failure of the backlight.
If this is the fault, you can connect a known good signal and turn the tv on, an image can be seen by shining a torch at an angle to the screen.
As you are a self confessed amatuer, the standard warning about fooling around with mains connected device is relevant.
 

tmink

May 27, 2021
2
Joined
May 27, 2021
Messages
2
Hi @Bluejets, thanks so much for your reply!
First, thank you for your emphasis on safety, I'm making sure to be extremely careful, and also making sure I am grounded (and the TV is unplugged) when touching any components to avoid any ESD.

I plugged in the unit and checked the backlight (both using the torch/flashlight method) as well as looking for any light bleed through from the back of the TV. Unfortunately, I did not see any picture at all with the torch method, and also did not see any light bleed through from the back. So I have a feeling that not only is my backlight out, but I also might not have any picture generated on the LCD screen. One other piece of evidence that points me to believe that I have an issue in addition to the backlight is that I tested the ability for my computer to send audio to the TV speakers through an aux cable (audio jack). I tried cycling through the inputs but no input resulted in any audio output from the TV speakers.

There seem to be 2 separate backlight boards on either side of the TV (not pictured).

Orange power light changes to blue when turned "off"/"on standby".
controls-and-orange-power-light.jpg

Green light on Main Board is on when plugged into power outlet.
https://ibb.co/Svdh61r
main-board.jpg

Power supply board has white "dust" covering one half of the heatsink (not sure if on the "hot" or "cold" side):
power-supply-board.jpg


Please let me know what the next logical step would be in determining which board(s) to replace, or where the issue is. I have ordered a multimeter which will arrive tomorrow in case I need to test current flow to/from various components.

Thanks again for your help! :)

~Taylor
 
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