System build, keyboard doesn't detect, could this be the power supply? [DETAILS INSIDE]

[Vivtek]

So I'm trying to build a complete system, and essentially I'm stymied. I started with an ASRock 980ED3/U3S3 motherboard, an AMD FX 6300 CPU, 8GB of memory, Gigabyte Radeon R7 370 graphics card, and a Corsair CS450M power supply. Everything worked great, POST worked - but it can't see the keyboard (oh, just wait, this is only the beginning).

Did my homework: found two dusty old PS2 keyboards - neither worked. Tried the CMOS battery trick to recognize PS2 keyboards in problematic situations - no dice.

Call ASRock. The engineer tells me all the above steps, agrees it's time to RMA. I RMA. Hmm, I think, looking at the reviews for this board - let's switch to Gigabyte, because my own box (this is for a friend) has a Gigabyte board, never had problems with that. So I order a Gigabyte GA-970A-DS3P motherboard.

Install the CPU, and nothing happens at all. OK, I think, second mobo can't possibly be bad, I've surely fried the CPU taking it out. I RMA the CPU. The new CPU has the same problem. So OK, bad mobo -RMA the mobo (same Gigabyte brand) - no dice, same problem.

Gigabyte's site indicates maybe there's a BIOS incompatibility, so I order an Athlon to drop into it to upgrade the BIOS. Except the Athlon also stays dark. Zip. Well. That was a used CPU off eBay, maybe it didn't work?

Screw this, I say, I'm going back to ASRock, at least it gave me a POST screen, amirite? So I order the same ASRock again. Same keyboard problem! And I put the Athlon in it to confirm it works - the Athlon is fine, but the ASRock still doesn't see keyboards.

So at this point, four motherboards and three CPUs in, I'm forced to admit that the *only common denominator* was the power supply (before you say anything, I did actually try a different graphics card in there at one point, but I'm not 100% sure when). Could a power supply allow a motherboard to POST but not detect keyboards? Does that even make sense? I'm losing all contact with reality and common sense, and this has been going on for over a month (not full time, thank God).

 

[Vivtek]

Just a little more, here: I went to Best Buy and picked up a Corsair CX750M power supply, tried it with the ASRock mobo and the Athlon CPU (this is just what was still assembled), and it still didn't detect any keyboards. So not even that commonality is untested now. I am entirely at a loss. Thinking of trying an Asus motherboard just for laughs. Eventually *something* has to work.

 

[Chicano]

Well, it's almost certain the Asus motherboard won't work either... the only components you haven't mentioned and probably haven't tested is the RAM.. so that would be the next one to test.... if you have to, buy a cheap 1 or 2 GB stick just for testing purposes. You haven't mentioned AC power either... replace the AC cable, and the case is unlikely but it has rarely occurred that it was the cause for similar issues, so see if another case makes a diference or breadboard the system.

Computer case issue
http://www.tomshardware.com/forum/335331-31-computer-case-cause

 

[Vivtek]

the only components you haven't mentioned and probably haven't tested is the RAM.. so that would be the next one to test.... You haven't mentioned AC power either... replace the AC cable, and the case is unlikely but it has rarely occurred that it was the cause for similar issues, so see if another case makes a diference or breadboard the system.

You're right, I had also realized the memory is another common factor. I'll use the memory out of my own machine to try that end. The problem with the ASRock board is definitely not the case, because it was breadboarded (and still is at the moment), but that might have been the problem with the Gigabyte board, as it was installed in the case and I didn't take it out to retest (I had already received the RMA, so I figured there wasn't much point).

Multiple AC cables have been used over the course of this story.

Hmm. I will definitely try swapping out the memory tomorrow and see if that makes a difference. Thanks for the suggestion!

 

[Chicano]

I missed your last question on the original post...

Could a power supply allow a motherboard to POST but not detect keyboards?

Yes it can happen and I have experienced it several times.. twice with old computers and once with a more recent build... On the old PCs it was probably due to old motherboards, one failed soon after, the other one had bad capacitors, and the third (recent build) I didn't find a cause as I didn't give it much importance, I just double check all power connections and did a BIOS reset and issue was solved.... so either may have been the cause.

Another possible cause I can think of is USB port issues if you have USB keyboard and mouse connected to USB 3.0 ports. They don't normally work before you install USB 3.0 drivers.

 

[Vivtek]

Another possible cause I can think of is USB port issues if you have USB keyboard and mouse connected to USB 3.0 ports. They don't normally work before you install USB 3.0 drivers.

Ha, no, we learned that early on in the process. The ASRock motherboards don't detect *any* keyboards on *any* USB or PS2 port at all. Just sit there. And it turns out it's not the power supply anyway, because trying a different one results in the same problem.

It's very weird. This is our third build and we thought it was just going to be a cakewalk - and instead it's been a death march. 🙂

 

[Chicano]

Some power related issues are not the PSU but the AC source. So, just for the sake of eliminating every possible cause; have you tried another computer connected to the same AC outet, or connecting the new build to the AC source where the other computer is working normally?...

 

[Vivtek]

Well, it's almost certain the Asus motherboard won't work either... the only components you haven't mentioned and probably haven't tested is the RAM.. so that would be the next one to test....

Yep, you called it. I dropped my own RAM in it and it booted fine, so I tried each of the sticks we were using, and one worked; the other didn't. The weird thing is that it brought up a POST screen just fine but didn't say anything about the memory, and the ASRock engineer didn't *ask* about the memory when I called them with the very first motherboard.

Thanks for the clue!

 

[Vivtek]

Some power related issues are not the PSU but the AC source. So, just for the sake of eliminating every possible cause; have you tried another computer connected to the same AC outet, or connecting the new build to the AC source where the other computer is working normally?...

Just for the sake of humor, I should note that the first attempts were in Puerto Rico, and now we're in Indiana - so not only did we test with a different outlet - we tested with a different *power grid*.

 

[Chicano]

Just for the sake of humor, I should note that the first attempts were in Puerto Rico, and now we're in Indiana - so not only did we test with a different outlet - we tested with a different *power grid*.

Yeah, PR to US would discard the AC power source for sure... LOL

Bad RAM can even work fine through the BIOS Post and through part of the Windows boot and can even make Windows fully load, all depends on how bad the damage is... and the good stick may have contributed to hide the actual cause... and if the BIOS is set for quick post hiding the post text or part of it, that can be another reason the problem was not being declared... but as I said, bad RAM isn't always reoported by the BIOS and can appear normal. And may only show short of the installed total in Windows System information or third party system info programs.