[Solved] Motherboard beeps but monitor doesn't turn on

urbanium

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Nov 26, 2010
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When trying to boot my PC, the screen never turns on. The fans are spinning, and the light on the motherboard is on (I know this doesn't mean much :??: )

The mobo gives me 1 long – 3 short beeps which, according to the manual means no VGA is detected.

My first reaction was to try clearing to CMOS so I both removed my mobo battery for a while and also cleared it with the appropriate jumper. Is it possible that the mobo battery be out of juice after merely a year and a half of use? (bought new)

I also tried my RAM sticks one by one and in different slot, nothing helps.

After reading quite many topics on this forum, I decided to change my PSU (I had a very cheap 420w) and bought a Corsair 550W. If it didn’t help, it wouldn’t hurt to change it anyway. And indeed it did not work.

At that point decided that everything was pointing at the graphic card being defective so I went to the store and bought a new card. That did not solve the problem either.

I seem to be left with either a dead CPU or defective mobo.
I read in several places that since my motherboard still gives me some error beeps, my CPU *should* not be dead. (can anyone confirm this?)

Now, I’m thinking that the PCI-express slot is damaged somehow. I tried to look closely and noticed that one of the pin isn’t visible anymore. And also there is some residue of glue (!!!) around (and maybe inside, I can’t really see) the slot because the genius who built the PC thought it would be wise to get the card in place with glue.

I don’t have any other PC handy to test my hardware unfortunately…

Does anyone have any opinion on this?

Specs:
Mobo Asus P5QL PRO
Intel Core 2 Duo E8500
4GB DDR2 RAM 800
2 graphic cards I've tried:
-GeForce 9800GT 1gb (old)
-Asus ENGTS450 DIRECTCU TOP (brand new)

Thanks a lot in advance!
 
Before going further, verify the monitor (and the monitor's port) are working correctly, ideally by using on another PC. Then try another cable. A failure at any of those points (from the monitor back to the motherboard) can cause this problem.

If its still fail, now the problem is isolated to the motherboard/slot.
 

jsc

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Start over from the beginning:

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-posting-boot-problems
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 beeps 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-breadboarding

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

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.

Motherboard LED's mean very little. When on, all they are telling you is that the computer os plugged into a live power socket and the PSU is switched.

Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
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=youtube_gdata

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.

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.
 

urbanium

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Nov 26, 2010
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Hi again,

I just wanted to come back and say thanks to whom replied to my thread. My problem is now fixed...the defective part was indeed the mobo (most proably the PCI-e slot...) I have invested in a PSU too (like I mentionned before) which I think is not a bad decision anyway. So all is fine now and I have learned how to install a CPU on a motherboard at the same time :)
Thanks again!
 
If you haven't done so, don't forget to makes sure - right now - that the old psu will also power the new setup. All that is required is to get it to boot into windows - no need to "push it".

If it works, save the psu. Sometime in the future you will need to swap in a "known working psu" in order to debug a hardware problem.
 
G

Guest

Guest
Hello ,same problem
Windows starts,monitor ramains black 5 min after that it displays the desktop
used the monitor on a diferent PC works perfect
Used a diferent monitor on this PC works perfect !
I dont get it
 

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