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Computer turns on but no video

Last response: in Systems
November 13, 2011 10:08:33 PM

Gigabyte GA-990xa-UD3 MD
Corsair Vengeance 8GB (2x4GB) 1600HHz
HIS Radeon HD 6770 IceQX video card
Corsair GS800 PSU

My computer turns on fans run but im not getting any video to my monitor. Tried the trouble shooting before posting nothing worked even tried bread boarding still nothing. Also the mouse i tried would get power and then loose it (the light on the bottom would flicker then turn off), I tried a different mouse and it seems to be working fine but im having the same problem with my keyboard.

More about : computer turns video

a b B Homebuilt system
November 13, 2011 10:53:45 PM

Do you have access to another video card to swap in for troubleshooting? I assume you never see anything on the screen (even the BIOS splash page). Is that correct?

Also, verify that both your 24-pin and 8-pin power connectors (from the PSU to the motherboard) are firmly attached.
November 14, 2011 12:19:01 AM

Both are connected firmly and no i dont have another video card to swap and yes nothing on the screen
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November 14, 2011 1:34:01 AM

No beep at all? That could be anything, i'm afraid...
Did the harddisk spinning? You might be able to check the led indicator for this.
Have you tried changing/swapping the ram?
November 14, 2011 2:20:00 AM

it doenst have a speaker saddly and i looked all over and couldnt find anywhere to buy one and im not sure if the hard disk is spinning which led is it the one on the fron of the case is solid or blue
a c 122 B Homebuilt system
November 14, 2011 2:37:42 AM

The following thread (our standard troubleshooting thread) also has a source for the system speaker. Because your system is not POSTing successfully, you really need one. You can also salvage one from an old case.

Work systematically through our standard checklist and troubleshooting thread:
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If that doesn't help, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.

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, 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: 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.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

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.

November 24, 2011 11:08:16 PM

so i tested my power supply and it all the voltages checked out but when i hooked it up to the mobo the grey wire didnt go to 5V it went to 4.3V is that a problem