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Computer Repair with Diagnostic Flowcharts
- Your First Sale
- From Hobby to Self Employed
- Buying and selling hardware
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- Accounting and Taxes
- PC Customer Service
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Copyright 2012 by Morris Rosenthal
All Rights Reserved
Video Adapter and PC Display Diagnostic Flowchart
Warning! You must unplug your ATX power supply from the wall before working inside the case.
The video failure troubleshooting below is one of the 17 diagnostic flowcharts from my book, "Computer Repair with Diagnostic Flowcharts Revised Edition." As PC technology has continued to develop in recent years, the old general purpose video cards have nearly disappeared. These days the video is either handled by an integrated motherboard controller or an expensive video gaming adapter that employs more raw computing power than the CPU. Every diamond symbol on the flowchart is linked to text that explains what the abbreviated flowchart messages mean.
Video Card Troubleshooting
If you aren't sure whether or not system power is coming on, see the flowchart for power supply troubleshooting.
Do you see anything on the screen of your LCD or CRT monitor? This doesn't have to be your Windows desktop appearing, any text or scrolling messages counts for "anything" in this step.
Are you sure the monitor is powered and turned on? Don't laugh. All LCD monitors have some form of status light, usually right above the power button, to tell you when they are powered on. Older CRT monitors have status LED that lights up when the monitor is powered and may blink or change color depending on whether there's an active video card driving it. CRTs (Cathode Ray Tubes) generally make a noise when they power on, a combination of static cling and something like a rubber band being strummed once. Both types of monitors, LCDs and CRTs, normally utilize a detachable power cord, so make sure the male end if fully seated in the monitor's power port. If you still aren't getting any signs of life from the monitor, try a different power outlet.
You may encounter an old LCD display with an external power supply, similar to the AC adapter for charging a laptop battery. If you have such an old LCD and it's not powering up, use a multi-meter to check that AC adapter output is approximately the same as the faceplate rating. In all cases, LCD displays are designed to take up the minimum of desktop space, so the tend to have the power cord plug in vertically, in parallel with the LCD screen on the back, rather than perpendicular. That means make it hard to inspect the connection, so just make sure it's in as far as it goes.
Funny stories are great when they're about somebody else, so don't be the guy who takes his monitor to a repair center only to be told that the controls were turned all the way down. This was far more common with old CRT monitors with exposed brightness control dials that could be accidentally turned all the way down. LCD monitors can save user settings as well, though they don't have the kind of range to make the image disappear entirely. In any case, the simplest way to troubleshoot whether you are dealing with a monitor problem or a PC problem is to connect the monitor to another PC or laptop and see if it works there.
If the only message your monitor will display is something that includes the word "power" it's probably informing you that the video adapter in the PC requires additional power to operate. The video card is alive, it's generating the message, but the motherboard slot doesn't supply enough power for it to function normally. Both the current crop of PCI Express cards and the higher performance AGP graphics cards that preceded PCI Express usually require a dedicated lead from the power supply. If you've just built the PC, it means you forgot to connect the power supply lead or didn't make the connection tight. If it's a PC you just had open for a different reason, you probably loosened the power cord connection enough to break the circuit. But if the case hasn't been open since the last time you used the PC, either that power supply circuit has failed or there's a hardware failure on the video card.
These supplementary power leads come in many forms, from the old fashioned 4x1 Molex connectors used in PCs since the 1980's, to the dedicated PCI Express video power connectors on the latest ATX power supplies. Some video cards will accept multiple types of power leads, it's just a little extra real estate on the card, but others will force you to find an adapter to convert from an available connector to one the video card will accept.
Most monitors will light up with a text message telling you no signal is detected if there is a problem with the video cable coming from the graphics card, or the graphics card is not putting out a signal. While it doesn't tell you whether the problem is specific to the cable, the video card, or the PC not working at all, it does tell you that the monitor and its electronics are healthy.
Make sure the video cable is securely installed in the monitor's video port. Two types of video ports are currently in use, the newer DVI connectors and the older SVGA 15 pin connectors. If the connector includes screws on the ends, make sure they are snugged down, finger tight, into the receptacles. The older SVGA cables used a high density connector the included a triple row of five pins, and one of these could easily get bent and then mashed down flat if the connector was forced on.
Because it's easy to do, check that the monitor functions properly on another computer. When using a laptop to test the monitor, you may have to use the function keys to tell the laptop an external monitor is installed. Since the point of the test is just to see if the monitor will display something, it doesn't matter if the image is funky, scrolling or looks like you have double vision, because it may not support the signal format the video controller of the test computer is generating. If your LCD monitor displays a very faint image that doesn't respond to brightness controls, it means your backlight is out. If it's a newer LCD with an LED backlight, it's most likely a failure to power the LED strip. If it's an older LCD with a CCFL backlight, like older laptops, it's more likely the inverter than the CCFL tube. Monitor inverters sometimes buzz audibly when they are failing.
LCD monitors often support both DVI and SVGA connectors. If you are using the SVGA connector, inspect the pins to make sure they are all perfectly straight. If any are bent, you can try to straighten them with tweezers or needle nose pliers but if they've been bent over flat, they'll most likely break. It's normal for a few pins to be missing from the connector as long as there aren't broken off stubs, it just means they weren't supported by the monitor. But if you do have a broken pin, I recommend finding a replacement cable (ask friends if they have one around) before trying to solder on a new end. The last time I did one with my shaky hands, it took me a couple hours, and the replacement connector costs more than a factory manufactured cord.
New monitors often ship with both SVGA and DVI cables, because the cable cost is low to the manufacturer compared to getting a returned monitor when the customer didn't get the right cable. This means you might have a spare cable yourself, and even though your video adapter in the PC probably doesn't support both types (some do), all you need is a video converter plug, which is a standard computer/electronics store item.
SVGA Video Connector Pin-out
- 1-Red
- 2-Green
- 3-Blue
- 4-Monitor ID (Note: pins for ID bits often not present)
- 5-Ground
- 6-Red Return (coax shield)
- 7-Green Return (coax shield)
- 8-Blue Return (coax shield)
- 9 No-Connection
- 10-Sync Ground
- 11-Monitor ID
- 12-Monitor ID
- 13-Horizontal-Sync
- 14-Vertical-Sync
- 15-Monitor ID
Did the PC let out a long series of beeps when you turned it on? A long series of beeps is a common code for video card failure, but it doesn't mean the video card is bad, it may have just popped out of the slot. If you search the internet for troubleshooting beep codes, you should be able to find exactly what your PC is trying to tell you. But I mention that the long series of beeps is often video adapter failure in case you don't have access to the Internet because your computer monitor isn't lighting up.
Check that the video card is sitting down in the motherboard slot. You have to open up the PC for this procedure, so unplug the power cord first. Before opening the case, take a look for the location of the video port on the PC. If the video port located on one of the shiny stainless steel plates that are lined up one after another on the back of the case near the bottom of a mini-tower, you have an add-in video adapter. But if the video port is within a half inch of the USB ports, mouse and keyboard port, etc, the video controller is probably integrated on the motherboard, so check the manual before you bother opening up the case. Assuming you have an add-in video adapter, the only way to be sure that it's seated is to remove it and reseat it. Check both ends of the adapter at the motherboard level for locking latches before you remove the hold down screw and start pulling on it. After you seat the video card in the slot and close and locking devices, go ahead and put the screw back in, but make sure it doesn't cause the opposite end of the card to rise up as the end under the screw is pushed down.
If you couldn't find the meaning of the beep code, and reseating the video adapter doesn't fix the problem, it's likely the video adapter is dead or the RAM installed on the motherboard has failed. RAM failure is also a common, repeated beep code, which is why it's worth looking up which one you have if you can access the web. See the flowchart for troubleshooting the motherboard RAM and skip to that point for the swapping tests you can do.
Does the PC display the initial BIOS screen identifying the hardware and then freeze? If so, it's probably not a video card problem unless you just installed a new one, in which case there could be a conflict or compatibility issue.
Did the problem appear right after you installed a new PCI adapter and closed up the case? This type of failure is pretty rare with newer PCs due to dedicated slots for video cards being isolated from the PCI bus, but I try to support older generations of PCs that used plain PCI video cards on the flowchart as well. If this is the case, try uninstalling the most recently added adapter to see if it's a conflict.
While you have the case open, whether you have a high performance gaming video adapter or integrated motherboard video, check for the presence of an active heatsink (a fan mounted on finned metal) above the video processor. Some video cards for gaming are practically covered with a heatsink, and if the fan isn't active when the power is on, there's a real good chance it failed, causing the video processor to overheat and fail as well.
Does the Windows Desktop appear after stripping the other add-in adapters out of the system? If so, the only thing to do is troubleshoot the problem adapter by replacing them one at a time until the problem reappears, making sure you power down and unplug the power cord before each replacement.
If you just built the PC or replaced the motherboard, try the video adapter in another computer before throwing it away because it could be a simple incompatibility. Even if the PCI Express version matches or the AGP speed (8X, 4X, etc) matches and the adapter fit into the slot, it could be the video card brand was never tested for the motherboard brand. Some AGP video cards were supposed to support multiple speeds, which led to funky card notches and confused the issue for everybody.
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