I turned on the PC today and then started to walk away. It started to boot and then beeped really fast (not sure how many times but somewhere around 8-10). Something also popped up on the screen but I was across the room and it was gone by the time I got back to the machine.
Then the screen went blank and the fans all ran at high speed (normally they start at this speed and then slow down during the boot process).
Now when I turn it on, there are no beeps, and nothing comes up on screen. The fans run fast and never slow down. It doesn't even get to the BIOS prompt.
I'm not sure about the beeps since it doesn't beep each time.
I've swapped and re-seated each stick of memory. I've unhooked the extra hard drive, the extra video card, and the DVD-RW to lift strain off of the power supply (in case it's degraded).
I removed the CMOS battery in order to reset the CMOS settings.
I'm trying everything easy first even though it's not the proper troubleshooting order. I don't have a spare power supply big enough to handle the components so I'm hoping it's not the problem.
EVGA 780i SLI Mainboard
Q6600 Quad Core CPU
8 GB PC2-6400 RAM
2 NVIDIA 9800GTX+ Video Cards
Sounds like a pretty old machine. If that happened to me I would quickly reach a point where I would build another. The only thing you can do is replace suspect items with known good ones including the CPU & PSU. Even if you do find out what it is I'd sooner put the repair money into a new box.
One of my systems has an OC'd Q9550, 4 GB RAM, a GTX260 - a card which pulls about 25 watts more than a single 9800GTX+, a Gigabyte EP45-UD3P motherboard, 3 hard drives and an optical, and a Soundblaster card all powered by a Corsair 750TX.
Running 3 instances of Prime95 to load the CPU and 3DMark06 to load the GPU, it pulls 375 watts from the wall as measured by my Kill-a-Watt meter. Figuring 80% efficiency, the system pulls 300 watts from the PSU. And a 2D desktop load will be 50 - 75 watts less. You could use a decent 350 watt PSU for testing with a single video card.
I have tested the following beep patterns on Gigabyte, eVGA (680i), and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
Make sure you plug the CPU power cable in. The system will not boot without it.
I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.
You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.
If no beeps: Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.
At this point, because you do not have a video card installed, you can use a less powerful PSU.
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.
The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.
Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.
Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST. At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.
Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
Was at my wits end and just took everything out and cleaned the case (in preparation for new components I was going to have to order). Cleaned all the current components and then put MB CPU and psu back in and reseated the MB, reconnected the powersupply and it booted up with memory beep codes...added memory: video card beep codes....added video card: single beep.
Added the rest of components and it all works fine now..