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Fixing flat sceen TVs for fun and learning
Old 01-20-2016, 06:30 PM   #1
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Fixing flat sceen TVs for fun and learning

I recently 'found' two flat screen TVs that neighbors had put out for the trash. They look to be in good physical condition (no obvious cracked screens or other visible damage).

Googling the model numbers indicates that they are both about 3-4 years old. One is a 40" Sharp LED and the other is a 60" LG Plasma.

I'm wondering if these might be good hobby projects to repair, so I can learn a bit about flat screen TVs. I am a MechEngr by training and can do basic unsoldering and soldering, swapping out electronic parts like computer memory, etc. I can troubleshoot as long as I have a detailed guide to follow. I am not trained in electronics, by any means.

I've found a handful of youtube videos about repairing flat screen TVs. The guys who posted them seem to be repair techs, so, of course, they go through things sort of quickly and seem to skip some details (which might be critical for me to know).

I'd love to fix these at the component level (pop off the back covers, spot a few swollen capacitors, replace them and call it a day). If the cost of a replacement board is relatively inexpensive (assuming I could figure out which board is causing the TVs to not work), that would seem to be a relatively straightforward repair for me to do, also.

Several minor issues right off the bat: The 60" Plasma is missing a power cord (looks like nearby TigerDirect has a 6' one for $1.39.) I don't have the remote controls for either set (these can be purchased online for about $15-$20.)

I also don't know the reason why these TVs were discarded. I plugged in the 40" Sharp and the red power light came on and stayed on. Depressing the built-in buttons (input, channel up/down, etc.) didn't change anything. Without a power cord, I can't determine anything about the LG TV at the moment.

I'm looking for thoughts/opinions as how to proceed. Should I abandon any thought of working on these? Or should I just look for a possible easy fix (pop off the back covers and look for "bad caps" and try to replace them)? Or find a guide to troubleshooting (any suggestions?) and pursue that? Anyone know if a TV repair place (do they still exist?) might troubleshoot the issue for me (for a fee) and then I can order the needed part(s) online and do the repair myself? OR In the interest of keeping these out of a landfill, is there an easy means of getting these into the hands of someone who can use them for parts or whatever?

omni
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Old 01-20-2016, 07:06 PM   #2
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Get the manuals, of course. There are buttons on cabinet to turn on, change channels, pop menu.

My new Samsung 48 is plugged in, and has red light. Power on and should turn green. Bring up menu. That can all be done without remote.

Attach some source and change input through menu.
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Old 01-20-2016, 07:28 PM   #3
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It is not hard to replace the caps, provided you have some basic tools for desoldering. The problem is knowing what to replace. A TV can have several hundred caps. And some of them can be bad without obvious visible signs.

In theory, a technician or an engineer can troubleshoot by measuring voltages at various points to pinpoint the simple bad parts such as resistors and capacitors. More complicated failures would require probing with an oscilloscope. The problem is that schematics and design details are usually not available. And then, one often needs a board extender in order to mount a board away from the chassis to make test points accessible for probing.

If your TV is one of the more popular models, it may be possible to find enough info on the Web to replace the most commonly failed parts. However, there's no guarantee that some other caps do not also fail, if not now, then later. I do not want to make it sound so discouraging, but you must know that satisfactory results are not certain.

At this point, as you have nothing to lose, I would start by surfing the Web to look for people with the same models and who have been able to restore them. People often post the failed part numbers and their location to help others.
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Old 01-20-2016, 07:37 PM   #4
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Sams Photofacts were a great resource for third-party service documentation and schematics. The local county library around here actually maintained a collection of them.

edit: looks like you may be in luck. They appears to still be around and show at least one flat-screen tv on the home page. https://www.samswebsite.com/

-gauss
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Old 01-20-2016, 08:16 PM   #5
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Without a power cord, I can't determine anything about the LG TV at the moment.
Can you temporarily use an extension cord? Cut off the end and wire/solder it in place to avoid paying for a power cord. Or use a computer power cord?
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Old 01-20-2016, 08:21 PM   #6
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Repairs can certainly be done but note that many modern components are tiny, surface mounted things, and thus tougher to work with than their bulkier 20th century counterparts.
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Old 01-20-2016, 08:28 PM   #7
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Many of these have just 2 pc boards. One is primarily a power supply, though it does do a few other functions. The other is the main board, sometimes referred to as the motherboard. There are several board replacement suppliers online. You may be able to spot issues like blown caps on the power board, the main board tends to be difficult to troubleshoot and most techs would say the time to do so would cost more than replacing it. There are several forums that have real tech on them that are willing to answer some troubleshooting questions. Good luck.
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Old 01-20-2016, 09:57 PM   #8
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My new Samsung 48 is plugged in, and has red light. Power on and should turn green. Bring up menu. That can all be done without remote.
I tried hitting the "Power" button and nothing changed. The light stayed red. Reading a bunch of things online indicates that this is how this particular model often stops working.

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Old 01-21-2016, 01:17 AM   #9
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Modern TVs or most electronics nowadays are tough to diagnose and repair, if the failed part is not something as simple as a failed cap. And as most of the ICs are digital, if they fail there is often just no activity, no signals to even probe around with an oscilloscope like in the old days with analog circuits. And even if you isolate the bad chip, you cannot get the part, nor are able to unsolder and to resolder a new chip.

The exception was the rash of electrolytic capacitor failures, but I thought that the industry has figured that out and resolved it. See:https://en.wikipedia.org/wiki/Capacitor_plague.

Even so, on youtube I saw a TV repairman replacing ALL electrolytic capacitors in a failed TV, and he said it was the only way to ensure the TV would not fail later. That means he replaced more than just the large capacitors in the power supply section, and did all the hundreds of small capacitors in all the signal boards. This was an older TV, and new TVs may have larger and more sophisticated ICs and the boards may be condensed to just one to make the job more amenable. I have not had a chance to open one of the newer ones up to look.
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Old 01-21-2016, 02:20 AM   #10
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Too many logic circuits on those PC boards to try and trouble shoot unless you have specialized test equipment. Your only chance of getting one of these TV's working is if it's in the power supply and even then, they are usually surface mounted components that require highly specialized soldering equipment that uses hot air so the iron never actually touches these tiny parts. (Static electricity reasons).
While circuit board might be shotguned out, there's no real way to tell if the replacement board works or not.

Unfortunately, these days TV's are not repairable in the conventional sense. Perhaps current models would get a remanufacture through the factory, but that's probably it.
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Fixing flat sceen TVs for fun and learning
Old 01-21-2016, 04:57 AM   #11
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Fixing flat sceen TVs for fun and learning

Quote:
Originally Posted by omni550 View Post
I tried hitting the "Power" button and nothing changed. The light stayed red. Reading a bunch of things online indicates that this is how this particular model often stops working.

omni

If you can find the same model in trash with a broken screen, it would be interesting swapping boards.

I would open it, using online video instructions. Probably will end up at electronics recycling. Does your town have that? Most do.
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Old 01-21-2016, 05:15 AM   #12
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Many of these have just 2 pc boards. One is primarily a power supply, though it does do a few other functions. The other is the main board, sometimes referred to as the motherboard. There are several board replacement suppliers online. You may be able to spot issues like blown caps on the power board, the main board tends to be difficult to troubleshoot and most techs would say the time to do so would cost more than replacing it. There are several forums that have real tech on them that are willing to answer some troubleshooting questions. Good luck.
That is actually encouraging IMHO. Power supplies are often the weak link in traditional TVs/monitors. Perhaps even more common than caps is a destroyed power semiconductor (ie transistor/FET etc). These are often large discreet devices mounted on a heat sink device. You can sometimes get an idea if they are shot with a 'diode-mode' function on a digital multimeter - especially if it is a dead short. This can be hit or miss because if you measure them in circuit, you will also pickup whatever it is attached too.

Any Internet tutorials that you can find about troubleshooting Switch Mode Power Supplies may be useful and instructive. I believe that Repair-Faq has one.

Please educate yourself on the electrical hazards within one of these devices before you open it up.

-gauss
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Old 01-21-2016, 07:09 AM   #13
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My DW's Cuisinart food processor gave up the ghost. DW found a youtube video that walked you thru replacing the start capacitor. Looked easy-peasy right.

I ordered the part online about 45 days ago. It arrived in the mail just the other day. The return address on the package was China! So now I know what it feels like to ship something by slow boat from China!

Anyway, replaced the cap. That didn't fix the problem. Oh well, I had only $3.49 invested in the project.
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Old 01-21-2016, 07:26 AM   #14
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I discovered that some of these TVs can stop functioning only to be restored with a reset - pressing and holding a specific combination of buttons. A lot of people don't know this and toss perfectly good TVs. After one of mine gave up the ghost I gave it to an old guy in the neighborhood who earns a little side income fixing them up. He has good luck with power supplies, swapping parts, etc. He said he gets pretty good results.
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Old 01-21-2016, 09:30 AM   #15
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I discovered that some of these TVs can stop functioning only to be restored with a reset - pressing and holding a specific combination of buttons. A lot of people don't know this and toss perfectly good TVs. ...
Excellent point! My Vizio TV locked up a couple times (some bug in the 'not-so-smart-TV' function), and only a very specific and non-obvious reset procedure would bring it back.

Do some searching on the specific model numbers. Sometimes the procedure varies even within a manufacturer.

As some are saying, it could be impractical to repair - many of the parts require very specialized soldering equipment and techniques. But it also could be something fairly simple. For the reasons you mention in the OP, it is definitely worth giving it a few tries. As long as there is a recycling place you can get it to, you've got nothing to lose (i'd be surprised that regular garbage haulers would pick these up - maybe they counted on someone grabbing them, like you did?).

My old Philips CRT TV gave out, and in no time my searching came up with a common fault in that model. One of the high voltage (ceramic, not electrolytic) caps would blow, and they said replace that (they gave a P/N for a 3KV rated cap to replace the 2KV rated original). Cost ~ $10 bucks including shipping (DigiKey, IIRC), replacement was easy, and it is still working. Just looked it up, July 2005, so more than ten years of added life - and this was mfg in OCT 1998. Wow, it might make 18 this year! I'm sure DW wishes it would blow, this is in her 'craft room' (son's old bedroom), so it uses a converter for this newfangled digital OTA broadcasts, and is in 'SD' only. I could buy a new one for her, but it's the principal of the thing!

Good luck, and 'good learning' if things don't work out!

-ERD50
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Old 01-21-2016, 09:53 AM   #16
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I discovered that some of these TVs can stop functioning only to be restored with a reset - pressing and holding a specific combination of buttons. A lot of people don't know this and toss perfectly good TVs.

I found a YouTube video which included a Service Menu reset for the 40" Sharp. I will be trying that out before I even open up the back of the TV. It would be great if that ends up being the "fix".

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Old 01-21-2016, 11:46 AM   #17
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I recently 'found' two flat screen TVs that neighbors had put out for the trash...........
Stretching this thread to include trash picking in general.........last month my neighbor put a Stihl chainsaw out on the curb. I took it home (after dark ), put fresh gas in it and it ran fine. I cleaned it up and sold it on eBay for $150 + shipping.

And people wonder what we do all day.
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Old 01-21-2016, 02:45 PM   #18
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If it were me, I'd pop off the back and look for the FRU (field replaceable unit) numbers, (aka part numbers for the big stuff). Then I'd check eBay. If it's a common failure, there will be someone from Hong Kong with a cheap knock-off. If cheap enough, I'd roll the dice on it. If not, I'd put the FRU's on eBay as "unknown - came from broken TV" and someone that's in your shoes will probably roll the dice themselves. Forget trying to replace components on a PC board, those days are gone.
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Old 01-21-2016, 03:15 PM   #19
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Stretching this thread to include trash picking in general.........last month my neighbor put a Stihl chainsaw out on the curb. I took it home (after dark ), put fresh gas in it and it ran fine. I cleaned it up and sold it on eBay for $150 + shipping.

And people wonder what we do all day.
Wow! nice score!
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Old 01-21-2016, 03:56 PM   #20
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The factory reset sounds promising.

I've fixed the power supply capacitors of many small components, including all my oldest Tivos. If they don't swell, you can also measure all the power supply DC output voltages, which are usually labelled, and see if they look correct. Then measure them again and make sure they have 0 VAC (no large ripple voltage). Replace any caps with bad DC or AC voltage. At least one Tivo actually had an adjustment for the 5 VDC level that I could use to lift a sagging voltage and get things working again.

I replaced several suspicious caps on my MIL's TV, but that didn't get it working. At that point you need more equipment, a good repair manual, and a lot more time. Or a quick internet fix. And in the end you have an old TV that's probably not worth what you put into it.
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