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 Post subject: LED TV repair?
PostPosted: Sat Jul 14, 2018 9:13 pm 

Joined: Sun Jan 15, 2017 5:03 pm
Posts: 165
Any of you guys savvy in the way of TV repair? Usually I scrap the boards but I had one that was what I thought an easy fix. I had to completely disassemble an LG LED TV to replace some LED strips however about 2 weeks past between dismantling and putting back together and I'm not convinced I put the diffuser pieces back in the right order. Logically I would think the hard plastic would go on the bottom (closest to the LEDs) as it would rest on the handful of plastic pins that jut out and then the other sheets on top of that and then the LCD screen itself....but the order in which I stored them would suggest the opposite. Needless to say, I put them in one way, put the TV back together, powered it on and all I got was a lit up screen with a weird look to it -- some rainbow-like reflections, extremely reduced viewing range from any angle other than straight on, etc (like I had things in the wrong order)...but there was no picture whatsoever so now I'm not sure if there's some other problem or if this is 100% tied to the order of the diffusers.

Any help out there?

I will say this...the 3 thin plastic sheets I kept stacked together so those didn't get shuffled and they appear to only be able to be installed one way (slots don't line up otherwise) so really the only possible change -- that I can tell -- is the location of the thick plastic sheet.


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 Post subject: Re: LED TV repair?
PostPosted: Mon Jul 16, 2018 12:50 am 

Joined: Tue Feb 03, 2015 6:57 pm
Posts: 4796
Location: Low DOS
You’re a bit outside my normal work area. So I’m totally guessing:

My first guess is a loose cable (or a connector too far in). You’d be surprised how much a loose cable can screw up. So make sure everything is seated properly. :note: remember flat wire isn’t like “3D” cable connectors. Putting the ends in all the way is not always the proper alignment. I see issues like this in old laptops a lot.

My second guess would be something somewhere grounding out wrong. A wire not fully inserted (again), a piece of loose solder, your daughter’s bracelet.. Etc. I take this from my extensive knowledge of BetaMax/BetaChord players; where a grounding issue that doesn’t burst into flames outputs garbage on the video channel, if anything at all.

My final guess is a blanked controller, depending on the age and brand.
A fair number of LCD units, from ancient to today, save system commands on an EEPROM chip. Static can flash it blank.
Assuming you don’t have one of the earliest LCD units with a socketed rom; Look carefully at the main board for an array of two or three small pins and a marking of PG, PR, ROM etc next to it. Epr was common in the mid 90s as well.
Any variance in erase(able) program(able)(ing)(er) ROM.
[pro note] also look for a set of two or three blank bare, filled in, through holes. Some manufacturers (LG is notorious) use these “pads” rather than pins to deter 3rd party flashing.
Actually that last guess is the majority issue for blank screens after a repair. And you can’t fault LG. If I was crazy enough I could flash Linux onto my smart tv and have a full fledged computer. But the big issue for them is that they sell the same tv at different prices based on the included software . And services pay based on inclusion. So if I flashed Kodi or MythT to my LG to get my Netflix they don’t get the contracted payment for that use.

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 Post subject: Re: LED TV repair?
PostPosted: Tue Jul 17, 2018 9:11 pm 

Joined: Sun Jan 15, 2017 5:03 pm
Posts: 165
I replaced both the t-con and mainboard (happened to have one of each laying around) and it didn't change a single thing in the tv display. I checked and reseated all cables. Still just a lit up blank screen...I wish I knew if changing the order of the diffuser panels could cause this or not...it's purely a guess and google hasn't been super helpful.


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 Post subject: Re: LED TV repair?
PostPosted: Wed Jul 18, 2018 5:00 am 

Joined: Tue Feb 03, 2015 6:57 pm
Posts: 4796
Location: Low DOS
Try asking at I foxit.com
Their people are truly the best when it comes to tinkering.

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-- my grades are my own and do not represent an offer from boardsort, nor are they guaranteed. Please keep that in mind.


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