Introduction: Fix a Malfunctioning LCD Power Supply
So I got five of these Optiquest Q9B LCD monitors from where my dad works, thinking I could use them for something other than monitors. The problem was, they just didn't even turn on. The problem was the same in all of them, so I'm guessing it is a pretty common problem for these monitors. I have also seen other LCD monitors being repaired this way, so it's worth a shot if your monitor doesn't work.
DISCLAIMER: The power supply in these monitors can potentially carry a lethal current in them. I am not responsible for anything that could happen by your following my instructions.
Not sure if that was necessary, but I want to protect my ass just in case...
Step 1: A Little Bit of Background
In LCD monitor power supplies, the capacitors will occasionally go bad. This causes them to leak and bulge out and the power supply will not be able to provide power to the monitor, causing it to not even turn on. So yeah, this is quite a problem if you want the monitor to work.
Step 2: Materials and Tools
You will need:
-Monitor that will not turn on
-Capacitor-you will find out the exact capacitor needed later
-Possibly a prying tool
-(optional) A solder sucker
Step 3: Disassembly
This is specifically for the Optiquest Q9B, but I'm sure most people could figure this out. First, take off the plastic part over the hinge for the stand. Then, remove the two screws shown in the picture. Now, all you have to do is pry the two halves apart with some way, shape, or form of prying implement. They should come apart fairly easily. Make sure not to break any wires possibly attached between the front and back halves. These will usually just be speaker wires, and I don't find them to be very important since I use external speakers, but still try to be careful. The power supply is usually covered, so take the cover off. Now make sure to unplug any wires going to the power supply, and take it out.
Step 4: Find Your Bad Capacitor
Now, on the power supply, you should see a bunch of capacitors. Most of them will look normal, but you're looking for a capacitor that has a brownish-yellowish crusty liquid coming out the top or is bulging on the top. The picture will show it better than I can describe it.
Step 5: Desolder
Now, fire up your soldering iron and wait a minute until it heats up. Mark the negative lead of the capacitor on the board for later use. The negative side is the side with the gray stripe on it. Then mark the capacitor that you need to take out and flip the power supply over, keeping track of the bad capacitor. Heat up the solder on one of the legs and use the solder sucker to remove the liquid solder. Do the same to the other leg now. If you don't have a solder sucker, just heat up a leg, bend the capacitor to pull the leg out a bit, and let the solder solidify again. do the same thing to the other leg and keep repeating until it is all the way out.
Step 6: Find Capacitor Value
Don't throw away the capacitor yet, look at it and find the value of it which should be printed on the side. It will probably not be the same value as mine, so make sure to check. Write down the value and throw away the offending capacitor.
Step 7: Selecting a Capacitor
So, this is where you take the capacitor value that you got from the bad capacitor, and find a new one. I used Digikey, but you can use whatever electronics supplier that you like. Select you capacitor using the filters, and then buy it. Isn't shopping fun!?
DO NOT USE A CAPACITOR WITH A LOWER VOLTAGE RATING!
*I skipped this step...I had the exact right one in my parts box.
Step 8: Solder in the Capacitor
Now that your capacitor came in, or if you just happened to have one in stock, you need to solder it back into the circuit board. Take it out of the packaging, place it into the holes where the bad capacitor was, making sure the polarity is correct, and then flip the board over and solder the new cap back in place.
MAKE SURE THE CAPACITOR IS IN THE CORRECT POLARITY! IT COULD EXPLODE OTHERWISE.
Step 9: Put It All Back Together
Now that your capacitor is replaced, plug all the cables back where they should be but don't completely put it back together. Turn on the monitor and, if that really was the problem and you did everything right, then it should show the monitor companies logo, or at least a warning saying, "No Signal". If that happens, then voila, put the case completely back together and it's complete and you can pat yourself on the back. If not, go to the next step.
Step 10: Troubleshooting
If you didn't get the desired result, then theres a couple things you can try.
-Resolder the capacitor in the other way. The capacitors polarities could be backwards, in which case, it wouldn't work.
-Try resetting the memory. I had this on a monitor once that would light up the indicator light but not do anything. I reset the memory, and it worked. Do a Google search for "reset __________ memory". Your model number goes in the blank.
-Try other methods. This might not even be your problem.
I hope this helps somebody, and now I will leave you to fix your monitor.