When I chose to build my first home theater computer (HTPC) and test it using a television with high definition, I was shocked that I had problems with "no signal." For those of you who wish to use a computer with your television, let me share with you some of what I knew previously and what I learned in the process of troubleshooting my first problem with a home theater computer.
There are three probable faults for no signal. The computer, the television, the video cable, or a combination of these three things.
Now if you do see a logo when you first turn on the computer but then video disappears, might we suggest you try adjusting the Windows video settings. Try entering the low-resolution boot option by pressing F8 just as Windows would start loading. Once in Windows, you can then try adjusting the video resolution until the problem is resolved. If the low-resolution boot mode does not work, then you probably have a bad video driver. This is of course based on there being some form of logo pictured from the computer when you first turn it on such as the brand of the computer or the motherboard.
When there is no signal, and before testing anything else, make sure the power is turned on. It seems silly but there are times when you may do a bunch of troubleshooting and then go to unplug the computer to move it for repairs to only realize that the computer was unplugged the whole time. This is the easiest problem to fix. Plug in and turn on. Check both the computer and the television.
If you suspect the outlet is without power, there is an easy way to check. Grab a lamp, radio, or any other electronic device you know works. Plug that into the socket in question. If the device works elsewhere but not at this outlet, you may not have power here. Some outlets are wired on a light switch, and it may be limited to just one plug so try all the sockets in question.
Does your computer shut off the power to the "display" after inactivity or go into Standby or a sleep mode. If so, try moving the mouse, pressing a key on the keyboard, or pressing the power button. If using a wireless keyboard or mouse, make sure they are turned on before attempting to wake the computer. Some computers wake when the power button is pressed. This can vary by manufacturer and customized settings.
The video cable
Video cables do fail. If you can, use a spare cable to test. If you have another HDMI or DVI device, chances are that you may have another cable, or you can usually purchase a cable for less than ten dollars. Simply swap out the cable and try again. You may know rather quickly whether this fixes the problem. If the television and computer are both turned on as you swap the cable, the computer may recognize the change and adjust the signal according to the EDID information provided by the television. Give it a few seconds. If after a few seconds the problem persists try restarting the computer. By default, Windows will attempt to identify the display it is connected to during start up. If you swapped the cable and you still have no video even after restarting the computer, then the odds are good that it is not a problem with the cable.
The computer
A computer problem could be anything from bad video drivers to failed video hardware. Here is the first way I identify if the problem is hardware or software: do I see a logo when I first turn on the computer? Most computers display a logo during initial power on while conducting some quick self-tests. If I see no logo when starting up the computer, then I suspect a hardware problem of some sort.
One possibility is that you do not have that video port enabled in the computer. Some video ports are built into the motherboard for integrated or onboard video. If you have an expansion video card as well, the ports on the motherboard are disabled by default in favor of the expansion card video. If your computer has an expansion slot filled with some sort of video card, you may want to check that you are plugging your video cable into an active port. It is an easy mistake to make. Just because your motherboard has the integrated HDMI port does not mean it will be an active port.
If you are using a video card that supports two displays and the other display is working, you may want to check in your display settings to make sure both "monitors" are enabled. This would be most evident if you have picture on the other display while showing picture on this television. It is becoming more common for computers to support two displays simultaneously, and some video cards support more than that. Activating a second display can usually be done directly through the Windows Display Properties or another utility for the display drivers. For example, AMD calls their video software the Catalyst Control Center.
If you still have no signal on the television, then if you have another television or a computer monitor available, trying connecting the computer to one of these instead. Some computer monitors support HDMI input. The purpose is to isolate if the problem is with the computer or the television. If you still get no video using a known good monitor or television, then the problem is with the computer.
If your monitor does not support HDMI, check and see if your computer shares a DVI or display port with the HDMI port you are questioning. The reason for this is because some computers share the HDMI port with a DVI port or display port. This is not a perfect test of the HDMI port. The best choice would be to plug a cable into the HDMI port with another television or monitor for testing purposes. If you cannot create the ideal test, you can get a basic idea whether the HDMI port should work if you connect a monitor to the matching DVI or display port it is paired with. If you still get no video using a known good display, then the problem is with the computer.
If the computer is still under warranty, I would recommend you contact your computer manufacturer/builder for support. If the warranty has expired or was invalidated, there are businesses with the skill to diagnose your computer located in most locations. Check your local listings. For example, in our local telephone book under "computers" there are several pages worth of businesses offering to repair computers, some even offering to come on-site to service your computer.
For those of us conducting repairs the easiest way to identify if it is a hardware versus software issue with the computer is to have another computer and compatible video card available. Do any part swaps with the computer(s) turned off. For example, after pulling the video card out of a computer, I found that the user's computer worked again when I turned it on again using only the integrated video port. I knew then that it was either the video card itself or the drivers in Windows. I was fortunate to have a compatible video card on hand that day. When I used my video card instead, there was picture. This eliminated the software and drivers as possible issues since both the software and drivers worked fine with the compatible video card. Since I had determined the actual problem was their video card, I was able to complete the correct repair and the end user was very satisfied with the work.
The television
Do you have another device that can connect to the same HDMI port as the computer was plugged into? If so, plug the alternate device into the television in the same port used with the computer. If this still produces no video, then there is a problem with at least the HDMI port on the television.
I bought a used television to use with my initial test HTPC. When I started having occasional problems with video, it turned out to be an indication that the HDMI port on the television was failing. It wasn't long before it completely failed. When I did a little research on the television online, I found out why the computer worked fine with my computer monitor but had troubles with the television. Other owners of that make and model television were having the exact same problem. What they found is that if they moved their cable box or gaming platform HDMI cable from port 1 to port 2 on the back of television that all their problems disappeared with both sound and picture. In this example, I was fortunate that the television had a second HDMI port to use and that this resolved the problem without having to replace the TV.
If the port on the television is failing, it could start sending bad information back to the computer. When the computer connects to any display it sends a signal requesting the device identify itself (EDID). If the television gives the computer faulty information, the computer will not identify that the television provided incorrect data. In our test rig, it was that faulty EDID signal, so the computer would end up sending incompatible signals. We could force the correct setting but whenever we changed inputs on the television, we had the issue that switching back to the computer caused a new EDID identification and the computer would return to a setting the television did not support.
Having corrected our issue with a faulty HDMI signal, I have had the opportunity to see more of the wonders of owning our own home theater computer. It has been better than anticipated once we resolved that one problem of "no signal."
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