No video signal - no green light on monitor
- Video card problem - possible short in VGA connector or connector loose
- Monitor problem - possible short in VGA connector
- Short in VGA cable
No POST, no video but green light, no beeps from computer:
- IDE cables plugged in backwards - some early ones were not 'keyed' and could be plugged in backwards.
- One or more RAM modules are seated incorrectly or not at all.
- If you have 1 RAM module, most boards require it to be in RAM slot 1
- Incompatible memory types - mixing EECs with non - EECs.
- One or more RAM modules are defective
- Dust on the RAM modules is causing a direct short somewhere. This dust is most often from the CPU fan since most RAM slots are located very near the CPU socket.
POST and beeps
- Check the number of beeps in the board's manual to find out the problem. Generally, one beep is either a keyboard error, hard drive error (can't find the boot drive), or floppy error. Floppy drive cables can be plugged in backwards which will cause the red light to stay lit. This will cause the drive to be unresponsive to any commands coming from the BIOS which will flag an error.
- 3 beeps - video card error. Video card is either being shorted out by dust on the card, is not seated properly, or has an on-board problem causing the 2D circuitry to be unreponsive to BIOS POST.
No power, no lights, no spin ups on hard drives - no responses
- Short inside of the power supply - a lot of stress is put on these power cables in order to reach many of the devices in the case. Often times these power cables will short out near the exit from the power supply and/or completely detach from the power supply motherboard. Check all power connections to all devices and ensure that the female and male plugs are connected correctly and solidly. Often times the metal tabs holding a wire in the plastic plug will break causing a bad connection to occur when mated with it's female counterpart. Replace these immediately - these can and will cause a hard drive to reset if they short out and will certainly result in lost data and/or a dead drive.
- Modern power supplies have a breaker built into them. When this breaker has been overloaded it trips and does not allow power to get to the motherboard. This can be reset by simply flipping the switch on the back of the power supply to zero instead of 1. Unplug the computer from the outlet or power strip and wait for a couple of minutes. Plug the system back in and turn the power supply to one, and turn the system on. The system should start. One sure sign of an overloaded and tripped power supply breaker is a flashing green power light or a flashing power light on the case. This indicates an overload has occurred.
- The power supply has burned up either due to age, excessive heat, and/or a massive power surge. If it is because of the latter you can bet there will be some fried components in the computer including but not limited to: video card, sound card, LAN card, CPU, CPU chipset, keyboard circuitry, etc. Basically anything that was plugged into the motherboard at the time of the surge.
- Onboard video is interfering with a 3rd party video card. Sometimes this causes an unresponsive system. Remove the video card and reboot. Go into the BIOS of the system and turn the onboard video off. Turn the system off. Plug in the video card into PCI slot 1 or AGP slot 1. If it is a PCI card, the video card must be plugged into PCI slot 1.
- Onboard video card (if equipped) has a problem. Purchase a 3rd party video card (NVidia or ATI), turn the onboard video off (via the system BIOS), install the new card, turn the system on, and install the new drivers inside of Windows using the CD that came with the card.
If you get absolutely no response from the system and you have checked that power is indeed getting to the power supply, my best estimation is that the internal power supply breaker has been tripped due to an overload, a sudden power outage, or a sudden spike in the line. This breaker is designed to protect your motherboard and if it has tripped then you can probably be assured that none of your components have been damaged.
If this is a video problem it is because the card is not taking interrupt 10h and the BIOS recognizes this serious problem and simply halts the system. The video card if it is a PCI or older ISA card must be in slot 1. Any other slot will not work. There can only be one 2D card in the system at any time. There can, however, be more than one 3D accelerator in the system. In the past card manufacturers would create cards that were simply 3D accelerators and nothing more. These cards do not take interrupt 10h and therefore can be installed along with a normal 2D video card (provided the drivers and hardware are compatible with the 2D card). The old 3DFx Voodoo series cards used to do this. This practice has since been discontinued, but when working on other people's computers - you can come across pretty much anything and everything.
Troubleshooting steps
- Get down to a bare bones system.
- Unplug all unnecessary devices from the motherboard.
- You probably will only have the CPU, memory, and video card (if you don't have onboard video) in the system.
- Turn the system on.
- If it works, then gradually one by one plug in a new card or new device and turn the system on.
- Repeat this process until the system becomes unresponsive. This is essentially process of elimination. This will identify for you which card or device is causing the problem.
