FLAT PANEL LCD SCREEN PROBLEM

[W2PFY]

FLAT PANEL LCD SCREEN PROBLEM.

 My son having been trained as an expert dumpster diver like his father, brought home a non-working monitor. I have absolutely no experience working on this type of monitor. So I got it open which wasn't easy and I don’t know for sure if I created a problem.

Before I go into that in case there is someone out there who has a bad LCD monitor, I got wind of the fact that faulty electrolytic caps were the most likely problems in these monitors. So I started looking around and noticed that two had bulging tops and the others were perfectly flat.  So I yanked them out and proceeded to measure them on a digital multi meter in the cap tester position. The 550 uf one read about 330 uf. The 1000 uf one read .184. They were both rated 25 WVDC. I didn’t have any of those so I stuck two 200 uf at 16 volts knowing both are under rated for the job.

Then I prepared to fire it up knowing that those two caps might explode.  I put myself behind a 16 inch thick piece of Lexan that had been formally used to test the effects of 50 caliber machine gun rounds. I felt safe now to plug it in and to my surprise, it turned on and the screen became brilliant.  

Now the problem is that on the lower right hand corner, the pixels seem to be all black with a smattering of other colors blended in. You can see this in the picture I have provided. What is the cause of this and can it be repaired?

[Mike/W8BAC]

What is the cause of this and can it be repaired?

The display had a hard hit and is broken. That goo at the bottom right is the liquid display juice leaking out. As far as I know, nothing can fix this.

I had an IBM Think Pad that hit the floor of Mexico City Airport hard. The display did the same thing. Negative outcome, Not Goood. Wish the news was better pal.

Mike

[Opcom]

agreed. strip it for the backlight. That might be useful for a project. If it is not LED, use care as the cold cathode lamps are usually very thin and easily broken.

[ke7trp]

The panel is trashed.  However, That might not be expensive.  Check the model and type of panel and search ebay. I recently got one cheap.  The light, Board and control board are the expensive parts.
C

[Todd, KA1KAQ]

Sounds like a victim of the Capacitor Plague, Terry:

http://en.wikipedia.org/wiki/Capacitor_plague

Ran into the same think here with a Westinghouse Flat Screen TV that Jen bought in 2008. Online reports from many other owners of them croaking within days of the 1 year warranty. I was about to toss it when my Scottish blood kicked in and I decided to fix it instead.

Sad thing about your monitor is, the damaged screen was probably not an issue until it got hurled into the dumpster.

[W2PFY]

Interesting read Todd. You know as time goes by I forget some of my basic training of the visual things that should be looked for such as bulging caps. Just the other day I re-examined a computer PS and sure enough, there is one bulging cap on it.

Unfortunately, I already took some parts off it so now it's junk. I guess I could reuse some of the caps even though they are suspect. Since they would be used in my stuff, I guess it would be ok rather than paying the man for some parts  

[Todd, KA1KAQ]

Well, we've had it drilled into us, been reassured for years and years how we need to replace all the old caps in our rigs because today's new caps are infinitely better, China has improve their quality, blah blah. They can and do still sell junk as do other countries. I was ready to toss the TV figuring there was nothing in it I could fix, probably a bad chip, cheaper to buy a new one than the parts. Part of the disposable society mentality.

Don't let go of those troubleshooting skills just yet.  

[flintstone mop]

Looks like you're on ebay, might think about buying a used one there.

Fred

[W2PFY]

Looks like you're on ebay, might think about buying a used one there

Yes I have an account on epay. I looked but there are very few replacement panels on there. If anyone finds a source on there, I would like to know.

Thanks Terry

[w3jn]

We use a bunch of professional grade LCD CCTV monitors at work - these things cost $1000 each.  One would think they might be immune from the capacitor plague...  however, when I got here there was a stack of dead monitors in the shop and all of them were victims of leaking capacitors.  I showed the techs how to troubleshoot and repair 'em.  The most time consuming part was taking the damn things apart.

These monitors have a SMPS that provides +5, -12, and +12.  Only the +12 is used, and that feeds an inverter board that supplies the +5 and -12; the latter board is where the bad caps are always found.  A needlessly complex and stupid design - why not just use the unused +5 and -12 rails off the existing SMPS?

There's a push to use LED replacements for fluorescent tubes as electricity overseas is very expensive.  These abominations use a PWM supply with - you guessed it - chinese capacitors.  So much for the vaunted "20 year" lifetime these stupid things promise.

[WA1GFZ]

A 20 volt cap of today is a 10 volt cap in past years.