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
-Soldering Iron
-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. Be the First to Share


We often get asked ‘How to fix a monitor that won’t turn on?’

1. Check your monitor’s connections

To begin with, your computer may not be broken at all. The first and simplest test is to determine if the problem is with your monitor or the connections between it and your computer.

2. Check the wall socket

If your screen is still black, see if the problem can be resolved by plugging in the monitor to a second outlet. Still no luck? You’ll need to go on to the next troubleshooting stage if this fails.

3. Check your monitor’s backlight

When your computer is on and the screen is entirely black, shine a light directly onto it with a torch. If you can see an image using only touch, the backlight on your monitor is probably broken, and you’ll need to replace it. This isn’t something anyone without technical repair knowledge should attempt alone because if you break your screen.

4. Check if it’s a problem with your PC

If none of the above-listed troubleshooting options has solved your problem it’s now time to test if you can rule out the problem being with your computer and knowing that it is a problem with your monitor or connections to your monitor.

5. Try with another monitor

If you have another monitor accessible (perhaps from a different computer in your house or even friends), utilize it to check whether your current monitor is defective. Simply unplug the device connected to your present monitor and connect the second monitor, which you know works. I’d use the other power cord and cable to do this. If the second/replacement monitor turns on, you can safely eliminate this as a cause of your computer’s problem.

6. Check the monitor’s adapter

The next step is to look at the supply of power to the monitor, including the cable. Some monitors are built with an internal or embedded power supply, while others are powered externally (similar to a laptop). If the power supply of the second monitor is interchangeable, I’d connect it to the first monitor’s power supply. If you notice that the screen still lights up, then there’s something wrong with the power supply. If the screen does not light up, there is generally a simple remedy that does not cost much. Your option may be to buy a new power adapter. However, before you go out and get a new screen power supply, first reconnect your original monitor to the second monitor’s power supply and see if it works. However, if this does not solve the problem, you may need to replace other components in addition to the power supply.

7. Make sure you have plugged in the right cable

This is simply a test to ensure that the power supply is working properly. Just make sure the cable’s connections to your computer and monitor are secure and durable. If your screen still works after you’ve tightened these up, you’ll feel silly, but it will provide excellent results. If this doesn’t work, try swapping the cables to see whether there’s a problem with the cable. If you have a computer and monitor that support a range of connection types, consider VGA (15 pin blue), DVI, or DL-DVI-D (white). If replacing your cable solves your issue, this is the easy solution If the screen remains dark, you may have a defective monitor that is best replaced rather than attempting to repair it. If you haven’t ruled out that your computer is faulty rather than the display, move on to the next phases of troubleshooting why your monitor won’t turn on.

8. Check the graphics card

If you have no prior experience repairing a PC, opening up your computer to examine the graphics card is probably a task for a technician. If you have the expertise, take out the graphics card and reset it in the PCI-e slot (or another PCI-e slot if your motherboard has more than one). If this does not work, then it is possible that your computer’s motherboard is broken.

9. Computer Motherboard

You can exchange motherboards to see whether this is the reason your monitor’s screen is black. This requires a large amount of work, and it’s not for those with little or no technical knowledge. You can also try plugging in another computer or laptop to see if you get any display. If you’re having trouble with a certain program or game, search the internet for an uninstaller. There are plenty of free uninstallers out there, so it’s easy to find one that works with your operating system and model. If nothing else works, maybe you should start over with something simpler. The RAM modules in your computer may need to be replaced. If after all of this troubleshooting you still don’t have a solution to your issue, get in touch with a local IT technician.


Actions This document pertains to HP desktop computers with Windows 10, 8, and 7. Troubleshoot a video connection from a monitor (or a TV being used as a monitor) to a desktop computer. If your computer has a built-in display, see Screen is Blank after Starting the Computer. This document will help you determine if the blank screen is being caused by the computer hardware, the video signal to the monitor, or the monitor itself.

Before you begin troubleshooting a blank monitor

Check the following items before using the steps in this document:

  • Make sure the monitor has power and the power light comes on when the power button is pressed. If the light on the monitor remains off, the monitor is not receiving power from either the wall outlet or the power adapter.
  • If you have a flat panel LCD monitor, unplug the monitor power cable, wait about 30 seconds, reconnect the cable and then turn on the monitor. This resets the electronics on the monitor.
  • If the monitor has a detachable video cable, obtain a second monitor cable for testing purposes in case the cable is bad.
  • Disconnect all connected devices except the mouse, keyboard, and monitor. This includes removing USB flash drives and memory cards from card reader slots.

Step 1: Check the power

Disconnect the video cable from the monitor and make sure the monitor power cable is plugged into a power outlet. With the monitor plugged in, press the power button on the monitor. There is a power indicator light located on the monitor case.

  • If power light remains off when you press the power button, either the monitor is not receiving power or the monitor is defective. Check all the following items before attempting to service or replace the monitor:
    • Make sure the power outlet has power and the power outlet matches the power rating for the monitor.
    • Connect the monitor to a different power outlet.
    • Try a different power cord.

    If the light comes on, the monitor has power. Continue to the next step.

Step 2: Check for fan noises, beeps, and power lights

To help determine whether the problem is caused by the computer or the monitor, turn on the computer, listen for sounds, and look at the lights.

  • If the computer makes a beeping sound when turned on, a card, cable, memory module, or processor inside the computer might have come loose. Go to Reseat loose internal components to check for loose components.
  • If you do not hear noise from the fans and the power lights on the computer are not on, the problem is related to the computer, not the monitor. To troubleshoot a computer that does not start, see Computer Does Not Start.
  • If you can hear the computer fan spinning and see lights on the computer, the problem is probably caused by the video cable connection or the monitor. Continue to the next step.

Step 3: Reset the monitor

At first setup, or under certain signal conditions, the monitor might not be able to switch to a new display resolution. Do not shut down or restart the computer. Instead, reset your monitor. If you need instructions for resetting your monitor, search the HP support website. Go to HP Customer Support, and follow the instructions to find your product. You should see the image from the computer on the screen. If not, continue to the next step.

Step 4: Check for error messages on the monitor

Use the following steps to see if a built-in on-screen message is displayed.

  1. Connect the video cable and turn on the computer.
  2. Turn on the monitor and wait about ten seconds while the computer starts.
  3. While the computer is starting, disconnect the video cable.
    • If the monitor remains blank, turn off the computer and continue troubleshooting.
    • Some monitors do not have on-screen messages but instead use the lights to indicate no signal. When you disconnect the cable, instead of an on-screen message, the light turns amber, indicating that the monitor lost signal and is working properly, but is out of range, or not receiving the signal.

Step 5: Check cable connections

Otherwise, check the video cable connection on the back of the computer and on the monitor. Make sure that it is connected properly and the connecting screws are tight. Turn the monitor off and then back on again (while the computer is on) to see if an image is displayed. Make sure that you have the monitor power adapter cord plugged into the power connector. After you have reconnected the power cord, turn on the monitor (while the computer is on) to see if an image is displayed. If there is still no image, continue to the next step.

Step 6: Connect the computer to another monitor

Connect the computer to another monitor to determine which device has the problem (the monitor or the computer). If you do not have an extra monitor, temporarily connect the computer to another monitor for troubleshooting purposes. After the monitor is connected, turn on the computer and the monitor.

  • If the newly attached monitor displays initial startup screen(s) but then goes black, there is a problem with Windows starting.
  • If the new monitor works, the original monitor or its cables are faulty. Try connecting the monitor with a different video cable. If the monitor still does not work, replace the monitor power cable. Replace or service the monitor if it still does not turn on.

Step 7: Inspect the video cable and video connectors for damage

Inspect the video cable and video connectors for damage. Check for sharp bends or breaks in the cable, or bent or broken pins at the connectors. With the monitor and computer off, try to straighten bent pins with a small metal tube, like the tip of an empty mechanical pencil or the tip of a retracted pen. If you had to straighten any pins, reconnect the monitor making sure that the video cable is firmly connected and then turn on the computer and monitor. If the monitor is still blank, continue to the next step.

caution: Do not remove the video port cover. If your computer came with a graphics card, HP may have installed a plastic cover over the video port attached to the motherboard. Most PCs can use graphics from the graphics card or the motherboard, but not both at the same time. If you remove the plastic cover to connect a monitor (VGA or HDMI), the video will not work unless the graphics card is removed. The better solution is to connect an adapter to make the connection.

Step 8: Reset the BIOS

In case an item was changed in the BIOS, such as the primary monitor device setting, use the following steps to reset the BIOS back to its default configuration:

note: You can use these steps even though you cannot see anything on the monitor.

  1. Turn on the computer and repeatedly press the F10 key about once every second for eight seconds.
  2. Press the Down arrow three times.
  3. Press the Enter key two times.
  4. The computer restarts.If the monitor is still blank, continue to the next step.

Step 9: Reseat loose internal components

If the computer case was recently serviced or moved, a card, cable, memory module, or processor may have become loose. When this happens, the computer might make a beeping sound when it turns on. Use the following steps to check for loose components:

warning: The edges of metal panels can cut skin. Be careful not to slide skin along any interior metal edge of the computer.

caution: This product contains components that can be damaged by electrostatic discharge (ESD). To reduce the chance of ESD damage, work over a non-carpeted floor, use a static dissipative work surface (such as a conductive foam pad), and wear an ESD wrist strap connected to a grounded surface.

  1. Unplug all cables except for the power. Note each cable location if you do not already know where it connects.
  2. With the power cable removed press and hold the power button on the front of the computer for 5 seconds.
  3. Remove the screw(s) that retain the panel or cover from the rear of the computer.
  4. Slide the side panel off from the rear of the computer. Image of a computer on its side with a side panel retaining screw called out and a directional arrow pointing to the rear of the computer.
  5. Gently press down on the outside edges of cards and memory modules that are inserted into the motherboard to better seat them. Do not apply too much pressure.
  6. Gently press down on the connectors of the flat ribbon cables to seat them.
  7. Replace the side panel and screw(s), reconnect the computer cables, and turn on the computer.
  8. If the monitor still displays a black screen or displays a No signal message, the video hardware may be faulty and needs to be replaced or serviced. If the monitor displays the first startup screen but then goes blank, continue to the next step.

Step 10: Change the display resolution

Use this step to configure Windows to use a display resolution that is compatible with the main monitor device. In order to perform these steps, you must connect the computer to another working monitor. If you cannot view the first startup screens, skip to Replace the graphics card or have the hardware serviced. Use the following steps to change to a compatible display resolution and color depth setting from a standard graphics mode. For flat panel LCD monitors, set the display resolution to the monitor’s native display resolution.

  1. Right-click Start, and then select Shut down or sign out.
  2. Press the Shift key while you click Restart.
  3. Click Troubleshoot, and then click Advanced options. Troubleshoot screen with Advanced options selected
  4. Click Startup Settings. Advanced options screen with Startup Settings selected
  5. Click Restart. Startup Settings screen with Restart selectedThe computer restarts, and then a screen displays with a list of options you can enable or disable.
  6. Press the 3 or F3 key to enable low-resolution video. Startup Settings screen showing the various startup options
  7. Wait until Windows opens.
  8. note: If you cannot select your monitor’s native display resolution, then update the computer’s graphics drivers and repeat this step.

Step 11: Disable power settings in the BIOS

If Windows was recently upgraded, Windows might be starting up into a Power Saving state and producing the blank screen before it loads. After Windows loads (about 2 minutes after turning on the computer), press the power button briefly or press the Suspend key on the keyboard to see if the computer comes out of a suspended state. If the computer opens into a suspended state every time the computer is started, use the following steps to disable Power Saving in the BIOS.

note: Connect the computer to a working monitor to perform these steps.

  1. Turn on the computer and repeatedly press F10 until the BIOS Setup Utility opens.
  2. In the BIOS Setup Utility, press the Right Arrow key, and then select the Power tab.
  3. Press the Down Arrow key to select Hardware Power Management, and then press Enter.
  4. Press the Right Arrow key to disable SATA Power Management.
  5. Press F10 to save the settings.
  6. Press the Left Arrow key, and then select the File tab.
  7. Press the Down Arrow key to select Save Changes and Exit, and then press Enter twice.

Step 12: Replace the graphics card or have the hardware serviced

If you have tried all the steps in this document and are still having the issue, the hardware is probably faulty. If the monitor does not work on another computer, the monitor may be defective. The monitor should be replaced or serviced. If the monitor works on another computer and the computer has a discrete graphics card, try replacing the graphics card using the following steps.

caution: Keep any items away from the internal area of the computer to avoid damaging the computer.

  1. Remove all memory cards, USB flash drives, and CDs/DVDs from the computer, turn off the computer, and then open the computer case.

    note: If you need specific instructions for opening your computer, search the HP support website. Go to HP Customer Support, and follow the instructions to find your product.

  2. Locate the graphics card.
  3. Disconnect any cables connected to the card and remove the graphics card.
  4. Install the new graphics card and connect the cables to the card.
  5. Plug in the power cable and turn on the computer.

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