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Boot problem - no vga detected

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December 18, 2010 11:39:27 PM

Dear all

I have a booting problem. My pc cant boot at all. It stops at the beginning and the monitor remains blank (no vga detected). The diagnostics leds stop to 2 reds.
It all started when I tried to add 2 identical ddr rams (elixir 256 Mb – pc2700u-cl2.5). The pc didnt recognized them and it begun the long periodically beeps. The diagnostics leds stopped to 3 reds. I turned back to my old ddr rams (1gb and 512mb) and for that moment the pc refuses to boot normally
I used and an other vga card (XFX 7300GS) but nothing. I used and the other pci slot and nothing.
I tried different combinations in DIMMs with my two rams (1gb and 512mb) and also nothing again.
Can you tell me about the possible causes and solutions to this problem ?

Thanks by now
Karathanasis B :pt1cable: 

MB : DFI Corp,LTD LP UT NF4 Expert
CPU : AMD Athlon 64 X2 4400+ @ 2200 MHz
DDR RAM : 1536 MB (Twinmos 1gb pc3200 cl2.5 and Samsung 512 pc2700 cl2.5)
VGA : EVGA GeForce 8500 GT
HDD : WDC (200 GB) and : WDC (80 GB)
WINDOWS XP
December 19, 2010 8:01:49 AM

nobody??
a b V Motherboard
December 19, 2010 9:45:05 AM

Reset the bios to bios defaults. Usually a jumper "CMOS" reset.Or unplug the power supply and remove the cmos battery for 10-30minutes or more..
Your board could not find a working setup for the mismatched ram.
Related resources
a c 238 V Motherboard
December 19, 2010 12:33:04 PM

+1 ^ reset the bios.

You are asking for problems with mismatched ram. Get a kit of supported ram in the size you want.

In the mean time, try to boot with the ram you know works.

Boot to a memtest 86+ cd; there will be no OS involved. You should be able to go a full test with NO errors.
a c 156 V Motherboard
December 21, 2010 11:10:17 AM

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
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 not, continue.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

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.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

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 or long single beeps indicate a problem with the memory.

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.
!