Dumpster TV Repair

In which I repair a TV I found in the dumpster

A while back I found a Samsung UN40F6400 LCD TV in the dumpster in the alley. Brought it inside and it seemed to work, although the backlight was not even in all spots.

Over time, it began to develop a problem where, during binges of The Great British Bake Off, it would occasionally go into this weird reboot cycle for 5-10 minutes. A moderate slap on the back of the TV seemed to fix it. Loose components maybe?

Recently, there was a power event in our building. I think a transformer exploded or something because when I was home for lunch I saw a giant spark and heard a loud pop near our front door. It was rather startling. Even though the AV equipment was on a surge protector, the video part of the HDMI inputs stopped working on the TV. Audio was fine, strangely enough.

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Hey the TV was free from the dumpster, so let's at least ses if it's an easy fix. First, I entered service mode by powering off the TV, then pressing Mute, 1, 8, 2, Power.

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Then I dug around the menus and ran some self tests and stuff and eventually came across some sort of status menu that said that all the A/V interfaces presented on the back of the TV were "Failure" or "NG" (no good). So maybe that power event fried some component that deals with I/O.

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I cracked open the TV so I could find a specific part number or something, and it turns out that modern TVs are pretty simple. It will a breeze to simply replace the mainboard. One popped up on everyone's favorite online auction site with some broken connectors, so I picked it up for $70 because I only really care about HDMI. The part number was BN97-07704.

Pro Tip: Use masking tape to attach the screws near their holes on large things like this. You're less likely to lose them because if you drop a screw there's a 97% chance it will bounce into a very annoying place.

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The replacement mainboard showed up, and it's a match. Looks like the replacement has a different style of heatsink on whatever chip to which the A/V interfaces route, and of course the broken connectors as described in the auction listing.

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Here are some additional reference images if you want.

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After a quick swap let's power it on and...

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Awesome. Fixed a dumpster TV for $70. Resist throwaway culture!

Later on, maybe I'll borrow my coworker's heat gun and swap the busted connectors. I also picked up a line conditioner for this A/V crap since this power event also seemed to fry the HDMI on my stupid receiver which I had to take to Deltronics to be repaired because I'm a caveman and that's waaaay too complex.

Written by fred on Sunday March 17, 2019
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