Repairing the Backlight on an LG Monitor (and Maybe Other Monitors) AKA the $9 Fix!

Greetings all!

DISCLAIMER: This project also involves electricity. If you're not comfortable with electricity (a.k.a. "man-made lightning"), you might want to give this a second thought. I'm still not a licensed electrical-anything, so it's distinctly possible that I did something that could/should have killed me and I just lucked out. This project deals with capacitors on an LCD monitor, and the word "capacitor" comes from the Latin word "capus" (I assume... I may be making that up), the root of which is "cap," meaning a jaunty hat or a slang term for whackin' a chump, as in "this capacitor has the ability to cap yer butt, resulting in your death or incapacitation." Use caution.

I still haven't figured out how to take non-blurry pictures (technology hard), but this time I did a better job of keeping my gigantic mitts out of the pictures. Mostly.

This particular monitor is an LG W3000H, so while this is specifically geared towards that, it might give you a general idea of how to approach a different monitor which is also having this problem.

A couple sizes of phillips-head screw drivers. I have a nice kit I got from Amazon a while back that I've found very useful: https://www.amazon.com/gp/product/B071PB4RPV/ref=p...

A stiff putty knife for prying apart the plastic case. Probably not an electronics-approved tool, but I was careful and it did a great job of not hurting the plastic. Much better than a flat-head screwdriver, so... I'm improving.

Replacement caps. Look at your caps and make sure you get the correct ones. In my case, these were the ones that I needed: https://www.digikey.com/en/products/detail/panason... I needed 4, so that was a whole $3, and the shipping was another $6.

The capacity to de-solder the old caps and re-solder the new ones. (See what I did there? Yeah... sorry.) Anyway - a soldering iron. I was surprised by the way these were attached, which made it REALLY easy - a basic soldering iron is all you need.

This monitor has been my main screen for a long time. Maybe 10 years or so. Early last week I turned it on and it looked like the dramatically-recreated picture above. Almost completely dark, though still identifiable to the computer as being there and "on." It also sounded like a summer evening in upstate New York - the buzzing of a thousand bugs in a nearby field wafted through my office, which is in Los Angeles, so bugs are mostly illegal and not something you hear 'round these parts. Turns out it was the capacitors on the... I'm going to call it the LED driver board. It probably has a proper name, but... me mechanical guy.

Remember... man-made lightning bad.

I've read a couple of things - one said that leaving the monitor unplugged for 20 minutes or so should make all the caps safe, another said it's more like 24 hours. Either way, try not to touch stuff in there if you don't need to.

You may need to remove the stand from the case first. I'm using a bracket in the VESA mounting holes connected to a thing on my desk, so that came off to move the monitor so I could work on it. I think the original stand also used the VESA mounting holes, so just unscrew the 4 screws holding it on.

There are two screws on the back of the monitor towards the bottom (see picture). Unscrew them, then carefully begin to pry apart the front and back of the monitor. I used a number of tools, but the winner was a stiff putty knife and a butter knife. If you go that route, make sure you don't shove it too deeply inside, since there's electronics in there and you might break something. Be gentle. Also maybe use a clean butter knife or you'll get butter everywhere.

The long edges on the top and bottom are a good place to start, and the corners are really hard. Take your time and work your way around the perimeter unlatching the plastic latches. Once I had a couple of corners done on one side I was able to pop the whole thing apart.

There's a little control board attached to the front frame of the monitor. It's connected to the inside stuff (called "the guts" by the cool technical people, though I might be making that up) via a little plastic plug thing. Unplug it. I was able to grab the plastic part with my fingers, but a tool of some kind (pliers or tweezers) might be helpful. I just know you shouldn't pull the wires directly - grab the plastic part.

At this point, everything should come apart into 3 pieces - the front frame (with control board), the back frame, and the guts.

Put the guts screen-side-down on a towel to make sure the screen doesn't get messed up.

If you're experiencing the dying monitor scenario where you turn your monitor on and it stays on for a few seconds then turns off, you'll need to access the power board, which is somewhere in the main guts. Take a look at my other Instructable for the general steps to address that issue (although it's a different monitor, it'll still give you an idea of the general process): https://www.instructables.com/Repairing-an-Acer-X1...

In the case of the problem I was having, I needed to access the LED driver board thingy, which is way easier to get to than the power board.

If you're looking at the back of the monitor in its correct up-down orientation, the part we're looking for is on your left. If you're looking at the first picture in this step, the bottom of the monitor is at the top of the picture, so what we're after is on the right.

There are two screws holding down the metal cover.

I rotated the monitor so the board we're interested in was facing me, so all the pictures from this point on are taken with the screen down and the bottom of the monitor to my right.

Unscrew the two screws and the metal lid will lift up, hinged by a piece of tape. No need to undo the tape - just fold the cover back out of the way.

Three screws and a strip of glue hold down a plastic shield of some sort. Unscrew the screws and gently peel the plastic shield off the glue strip. This will give you your first look at the caps.

There are 4 caps on this board, and mine were yellow (which means nothing), 35 volt, 270 micro-Farad capacitors. If the caps have signs of venting or bulging (see pics), they need to go. They were attached with a "solder blob" method that I hadn't seen before, but that made them really easy to replace. More on that later.

Even if some of your caps look pristine, I'd say to replace them all - it's really cheap and easy.

I use little paper or plastic cups to hold my screws and other hardware as I disassemble things, because it keeps them in one, easy-to-knock-off-the-table location. If you manage to not knock them off the table, you'll know exactly where to find them when it's time to reassemble whatever you're working on. If you do knock them off, it's at least decisive. None of this "one screw missing" garbage. If you add a poorly trained dog with an unnatural attraction to paper cups, it can become a fun game of keep away. Ask me how I know. If you're lucky, you won't have to retrieve any screws by tying a magnet to a string, coating it in peanut butter, getting the dog to swallow it... etc.

Anyway, my method is to stack the cups by steps. In other words, I put the screws from the first step in a cup, then put a second cup inside that, wherein I put the screws from the next step, then another cup, etc. It not only keeps them all together, it keeps them in order. I can't possibly accidentally use the outer case screw to reattach the board because those screws are several cups deep. The screws I can see in the top cup are the ones I need to use up before I can go to the next cup and the screws in it.

Here's one of the things I messed up and where you can learn from my mistakes. I took the screws out first, then disconnected the wires from the board, and then figured out I should have done the connectors first so the screws would still be holding the board securely.

There are 12 connectors and 3 screws to remove in this step. Start with the connectors.

At the "top" of the board (the way we're looking at it) on the left-ish side is a thin, blue-tipped ribbon connector that just carefully pulls out. I looked for a latch like I've found on this type of connector in the past but there didn't seem to be one and I didn't want to pop the connector off the board by trying too hard to make something open that doesn't.

Going clockwise from that location is the main connector (and again, I'm making up names for all these things). It also just pulls out, and I carefully used a flat-head screwdriver to get it started.

The right side connector has a snap latch thingy on the top of it. Pushing down on the tab all the way to the right lets the latch release and you can unplug it.

The same is true for the 9 LED connectors along the bottom.

Now you can remove the final 3 screws, and the entire LED driver board will be free.

At this point you'll see the plastic shield is connected to the back side of the LED driver board. I began to peel mine off so I could get to the bottom of the board to access the through-holes for the caps, only to discover that they don't go through the board. They're actually soldered to little pads on the top of the board by blobs o' solder.

Because of that, I just folded the plastic shield out of the way so I could work on the board and just left the shield attached.

Bend the caps up and away from the board so you can get a grip on them. Hold your soldering iron on a blob of solder, gently pulling the cap away from the blob as it melts, then repeat on the other leg of the cap. Easy-peasy. Do it for all 4 caps.

I should point out that the caps I ended up getting (these guys: https://www.digikey.com/en/products/detail/panaso...) were a little shorter and fatter than the original caps that were in there. The result of that is that they don't lay down into the cutouts in the board as much as the originals did, but there's still plenty of room in the space around the board when it's reinstalled, so I'm fine with it. If you want to get a better match, the originals are 15 mm long and 8.25 mm in diameter. (In America, that's .591" long and .325" in diameter, but good luck searching using those dimensions. It's almost like the rest of the world uses the metric system for some reason... Hmmm...)

I trimmed the legs on the new caps so they were about the same length as the old caps' legs - I just eyeballed it.

I tried two different approaches to replacing the caps, neither of which have pictures to go with them. Sorry. At this point I feel the need to reiterate that I'm a mechanical guy, not electrical, so... For the first two caps, I removed the old solder completely (down to the bare pad on the board). I found that the next thing I had to do was put down a blob of solder so the new cap leg would have something to stick to, so unless the old solder is somehow... old... expired? No longer good? I'd suggest you save yourself the extra work and re-use the existing solder blobs. It worked for me.

Remember that polarity matters. In this case, the negative side has the shorter leg... what do you mean you trimmed them to the same length? Who told you to do that?!? Me??? Oh... Not a problem - it's the leg that has the stripe above it on the body of the cap. In the case of the caps I got, the stripe has rectangles on it that I eventually figured out were minus signs. It would have been a little clearer to me if they were filled in, but I got there eventually.

If you were using my stack o' cups method of hardware organization, this part is a breeze.

Put the board back in place and secure it with the 3 screws along the top.

Gently push the blue-tipped flat ribbon cable into its socket.

Push the main controller connector into its socket.

Snap the right-side connector into its socket. It makes a nice little click when it's in.

Plug in all 9 of the LED plugs (they also snap into their sockets nicely).

Let the plastic shield flop back onto the board and secure it with its 3 screws. I also ran my finger along the glue line in case it was stuck down for a reason. Not sure it did anything, but it made me feel like I was helping.

Hinge the metal shield down into its position and secure it with its 2 screws.

Plug the guts into the control panel that's still inside the front frame.

Snap the front and back plastic frame parts together.

Screw in the last 2 screws that hold the frame together.

Reattach your stand or VESA mount or whatever you've got going on there.

My monitor looks just like it did on day 1. So... $9 and a really tiny bit of work and it's like having a brand-new monitor. Woo-hoo!