Repairing a broken LCD screen with a network switch

One of my monitors (yes I have many) decided to fail on me about a month ago. It is a LG 204WT that was purchased and used for a couple of years. The symptoms consisted of the LED power light blinking, and occasionally, the screen would seem to be attempting to get the video going before going dark once again. A quick search of the Internet showed that this apparently is a common issue with this monitor, where the most common resolution resulted in throwing the monitor out in the garbage making you worried that some hoarder is going to come sift through your stuff while making a mess on your lawn trying to find it. I hate throwing out useful technology before the end of its life span, so I decided to challenge myself to see if there was an easy way to fix the problem. Since it's not really worth spending money to fix (except maybe $5) given the price of new monitors, I decided to extend the challenge to see if I could fix it without spending a penny.


Now monitor and TV failures is all to common, and manufactures at times intentionally build them to only last a few years by putting in cheaper electronic components. This also makes them cheaper to manufacture, lowering the cost. The price of these things today is silly (cheap), so it is understandable. The biggest problem is that when something fails, you throw everything out in the garbage and buy a new one. Kind of like when you want to upgrade an Apple device.


The most common component to fail on a TV/Computer monitor (which is really the same thing) is the power supply. More specifically, the capacitors in the power supply. Now this doesn't mean that the power supply IS the problem, but it is a good place to start. Capacitors can easily fail in other areas of the unit, but typically the largest ones are in the power supply. The following semi walk through can be used for any monitor/TV really, as they are all very similar inside. If you are not comfortable getting your hands dirty with electronics, then stop now. The garbage is in the other room.

Opening it up

Now opening up this specific monitor is not easy. A lot of them you can just unscrew the back and get started. For this specific monitor, you need to wedge a screw driver between the front part of the monitor casing (white), and the back part (black). Once inside, delicately pry them apart. Once you manage to get one of the fasteners unlocked, just move along the side from there unlocking them one by one. Ignore the label that says "Do not open, this unit isn't user serviceable". I'm on to you LG.

Once you get the back/front off, it'll look like this.

Getting this thing open sucked. I hate you LG.

The board on the bottom is the power supply. Note where all the cables are connected (I took the above picture instead) and remove them from the board. Unscrew the board from the chassis.

Checking the capacitors

 

Now there is a chance that the problem isn't related to the capacitors. The first thing you should do is check everything out and look for obvious signs of burned out components, or fried continuity sections on the board itself. If you find a giant glob of burnt ketchup, you've learned that eating around your computer isn't a good idea, and that you are a nasty pig. If everything looks good, we can move on to the capacitors themselves.

If the LCD unit has been recently plugged in, it is very advisable that you discharge the capacitors before continuing. The best way to this by connecting a resistor to both of the leads. If you have a strange enjoyment of pain, you can remove your clothing, rub oil over your naked skin, and touch the capacitor with your finger for it to discharge into you. Charged capacitors are essentially tasers, and some can store a significant amount of energy. If you are not a freak, a resistor or any device that can drain the load is best practise. Otherwise, find something insulated you can hold on to that is grounded, then connect the two leads. I personally don't worry about tiny capacitors, but that is because I am a rebel that likes to live on the edge.

There are many methods you can use to test the capacitors to see if they are functional at all where there are no signs of damage.

Method 1 

 

The easiest way without a capacitance meter is to set your multimeter to measure resistance, and connect the multimeter to the leads of the capacitors (make sure the polarity is correct), and watch the ohm reading slowing increase from 0 to infinity (off the scale). This is the multimeter charging the capacitor.

If the resistance is 0 and stays there, the capacitor is dead.
If the resistance increases, but floats around an Ohm value for a period of time before increasing (if it does), then the capacitor is like a large male dear that was just hit by am even larger pick up truck at high speed. Sure it may be alive, but it is dying, and likely the cause of your problems. You should also call your insurance company.

Method 2

Method 2, otherwise know as you should really do this first but I wanted to educate you on testing capacitors. Check the capacitors for obvious sign of damage. If a capacitor is leaking, then you can breath in deep while flexing your chest to show how confident you are that you've found the problem. The capacitors may also look like this (mine)

LG Quality parts

If the tops of the capacitors are bulging (not flat), then the capacitor is bad and needs to be replaced. The tops of capacitors are are flat with grooves carved in them. When a capacitor goes bad, the pressure inside increases. The slits allow the capacitor to internals to expand so the capacitor doesn't explode under pressure. If you see this, you've found the problem.

Remove bad capacitors

Since 3 out of the 5 capacitors were bad in a single area, I decided to remove all of them. They are obviously terrible anyway. Thanks LG.

To do this you need a soldering iron. You can try blowing hot breath at it, but I doubt it'll work.

You may now remove the capacitors. Make sure you note the farad rating, and the voltage rating of the capacitor. It's probably also wise to note down where each capacitor goes, and what each polarity is. Putting in the wrong capacitors, or putting them in the wrong way, usually has amusing results.

This board has the polarity marked, so that saves a step.

The removed capacitor spots kind of look like the LG logo if it wasn't winking at me. Fitting.

Find new capacitors

This step usually involves searching a bunch of electronic component sites and selecting the capacitors you want, but paying $1 per capacitor + $15 shipping is more than a cent, thus, breaking my rules. You should probably order them though, especially if we are talking about an expensive TV or something. Make sure to get capacitors with the same  farad  rating (no matter what some smart ass says), and with the same voltage rating (or higher). Higher voltage is better, higher  farad   is bad. Get capacitors with a decent life rating at a high temperature. You don't want to do this again in a month.

Scavenger hunt

Now I'm tasked with finding free capacitors in junk I have lying around. The best place to find capacitors with high farad ratings is in other devices that have internal power supplies. Old computer power supplies, power bricks, or old audio equipment. I was about to try and open up a 8 year old IBM power brick (which isn't fun), before I remembered I had an old D-Link rack mountable switch that didn't work.

It's Christmas!!

Luckily, the main board had all 3 of the 1000 microfarad  capacitors I required, and the power cluster fuck (the black blob at the top) had the 680 microfarad capacitors I required. That was too easy! Now lets hope this thing didn't also die because of bad capacitors.

It's like a giant bowl of nerd candy

Once you remove everything that is useful, you can toss the remainder with pride that you recycled!

Put the new (or used) capacitors on

 

 I hope you can find where you wrote down where everything goes. Now is the time to solder them in the right spot, and the right direction. Don't worry, if you put any of them in the wrong way, they will only explode, scaring the living shit out of you.

That looks better

Once you're happy with the soldering job, now is the time to put everything back together.

Test your might

I had a step before this, but I was holding everything together and turning the monitor on with my tongue. Trying to take a picture would have probably resulted in being violently electrocuted.

Success!

If everything worked as expected, you should see the default monitor interface telling you that you're an idiot for not plugging a computer into it. Inform the monitor that it had a terrible accident, and that it just came out of the operating room. If the message is still flying around the screen, making fun of you, feel free to inform the monitor you've already replaced it, and that he'll be now a secondary monitor for your wife's computer. You can also tell him that the only reason he lived was because a piece of network equipment signed his donor card. I bet you feel stupid now for being racist against communications technology, you son of a bitch.

Back in one piece.