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Finding a new MoBo for my computer.

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April 19, 2011 7:20:51 PM

How would I go about finding out if a certain motherboard will fit my desktop PC (Dell Precision 300 I believe) I bought this (custom built) computer for really cheap a few weeks ago and it was fine, I left for the weekend and came back to turn it on and it's got what I'm 99% sure is a bad motherboard out of nowhere. Not sure what happened but if I can replace the MoBo for ~100$ that would be so awesome with my income/finances. I'm looking at a few on Newegg but not sure if what I will buy will be the right one/fit. Who's got the answers/help?

More about : finding mobo computer

a b B Homebuilt system
April 19, 2011 7:33:08 PM

Secondary said:
How would I go about finding out if a certain motherboard will fit my desktop PC (Dell Precision 300 I believe) I bought this (custom built) computer for really cheap a few weeks ago and it was fine, I left for the weekend and came back to turn it on and it's got what I'm 99% sure is a bad motherboard out of nowhere. Not sure what happened but if I can replace the MoBo for ~100$ that would be so awesome with my income/finances. I'm looking at a few on Newegg but not sure if what I will buy will be the right one/fit. Who's got the answers/help?


If it's really a Dell Precision 3-series that's a P4 machine and an antique. You'd have to scrounge for used parts. The additional bad news is Dell parts are almost always proprietary and you have to replace them with Dell parts, making finding replacement parts for old machines challenging and not entirely cost effective.

I'm a little confused because you say that it's a custom built machine, so is it new? Or just "new to you"? Does it have any warranty on it at all?

If it's really a P4 antique unless you can find a replacement board for free it's not worth fixing.
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April 19, 2011 8:12:08 PM

New to me. I'm pretty sure the Motherboard and whatever else aren't from Dell necessarily. A friend of a friend builds computers and he thought for some reason the video card was bad so he just sold it to me for real cheap because money isn't as important to him I guess. I hooked it up and there was no video card problems or anything. (That was one of the weird things about the whole situation. Whatever though) so what I *thought* I could do was just buy a MoBo and just swap them because I thought I was really just dealing with a case/size issue and nothing more. But, keep in mind I'm very new to all of this so I have no idea.
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a b B Homebuilt system
April 19, 2011 9:01:05 PM

It's possible your friend just re-purposed a Dell case and the actual innards of your machine are very recent.

What you need to do is open up the case under good light and take a really good look at what is in there. See if you can read any of the labels of any of the parts in there (do not actually attempt to remove anything) If you can get some pictures and post them we can probably take a very general guess at what century the machine is from.

It *may* be as simple as swapping a board (assuming the board is an issue, which it may very well not be) but the advice you're going to get here is going to depend on what hardware you actually have.
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April 19, 2011 9:16:03 PM

Alright I can do that when I get home. The reason I think it's a motherboard is when I try to boot up the power LED turns an amber/orange color for half a second before turning green and I get a six beep error. From the research and asking around I have done, I have found that it is most likely a MoBo issue. So you just want pictures of the MoBO and close up decent pictures of the insides and MoBo and then a list of whatever labels/markings I can find on the MoBo or on everything in the computer?

I honestly think that the computer I am dealing with is more along the lines of what you said in the first sentence about it being re-purposed and all that because everything looks new/updated and not old in any way.
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a b B Homebuilt system
April 19, 2011 10:48:17 PM


If you can open up the case and give us the make/model of the mobo (most mobos will have this on their face, but you may have to crane your neck a bit and squint and eyeball it) If you can't get a good read on the mobo make/model a top-down picture may help us guess what it is. Don't unseat anything.

The main goal right now is just to determine if the innards of your machine are Dell originals or something else.
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a c 122 B Homebuilt system
a c 156 V Motherboard
April 20, 2011 11:43:33 AM

If the system will not boot, try to fix it. Once you fix it, you can use a utility called CPU-Z to find out what kind of motherboard you have.

To troubleshoot the computer:

Work systematically 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.
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.
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, 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.
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