PC problem ?motherboard

[Ed Quinn]

I have had my system for about a year now and had a few issues in the past but this last week things went down hill fast. Now when I press the on button I get nothing not even the fan on the power supply starts. My system is running a Gigabyte 785G UD3A with an AMD black 7700 2.8 processor 2 gig of Crucial Ballistic ram (2x1gig) and a sapphire 4670 video card with 1 gig on it. The system for about 4 days would randomly restart no blue screen just a reboot as if I was just restarting it no error log nothing I thought it may have been a problem with the RAM I did have one bad chip when I first bought the computer and crucial replaced it. But now nothing not a thing when I push the on button ant thoughts not sure what to look at and yes the Power supply is and ANTEC earthwatts EA500 I have tested it per Antec by jumping the green lead with a black and yes the fan then turns on. The entire system is just under one year old.Also running XP sp 3 and have Panda Security Antivirus and spybot and adaware on the system no virus reported on the scans last week when it started this random reboot.

 

[SeanL]

Try removing the ram altogether and see if the system tries to boot before you replace the power supply - but it sounds like you have a faulty Mother board. If the system tries to boot with out the ram there will be a lot of beeps and then you can must try new ram

 

[jsc]

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.

 

[Ed Quinn]

Ok I have begun the process of following your step by step and I get no response what so ever. with just the Mobo and CPU hooked up and yes I have the speaker on the mobo. The power supply has no response. I did pull the plug on the case switch to check it with my meter and I show it is working it is open until i push and hold then I get good continuity. Antec is claiming the power supply is fine because the paperclip test did turn the fan on. Although the fan just barely runs, is their anything else I should try to ID if it is the PS or Mobo I am waiting for a new powers supply to come since I do not have another in house right now. I do recondition Dells from our recycling drives and I will say my experience is to change out the power supply first in 99% of the time I wind up with a running computer. If I do find out the power supply is gone do you recommend any one maker or should I stick to the Gigabyte list. This antec was on their list when I purchased the barebones system. How about the Mobo is it worth just getting a replacement or upgrade and to what? New mother boards are so picky with Ram I am concerned I have to replace that as well. I had a real hard time getting two good sticks when I bought the system. One stick was a little flakey and I got blue screens once in a while during the first month I owned the system.

I will keep you posted on the results as I work through this system issue

Thanks

 

[Ed Quinn]

OK New power supply arrived since this was untested I took the recommendation of going step by step and everything works 100%. Since I got no response from the old one other then the jumper test which did slowly turn the fan I suspect the power supply has a failure since it would not even turn on with just the mobo and CPU plugged in. Thank you for the guide it was extremely helpful going step by step.

best to all who responded Thank you!

Ed Quinn