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Issue I Just Can't Diagnose

Last response: in Systems
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January 12, 2011 2:01:47 PM

If this isn't the right section of the forum, please move the thread appropriately and I apologize.

Okay. So here's the dealio. I actually fix computers as a job, but I can't seem to figure out my own problem with my own computer. I've never had to post on a support forum, but I don't have any real ideas at this point.

Wake up in the morning to hear the fans on the computer whirring full-speed and the monitor in standby. Won't come out of standby. Weird. So I power it down and power it back up. I have 2HDDs and a DVD-ROM plugged into my SATA ports. The HDD the OS is on is not showing in the POST. Strange. So of course I get a "boot manager not found.". That makes sense if it doesn't see the HDD. Most of the time, I don't even get that far. Most of the time, I get a warning message. I hop into the BIOS to find that the 12v line is only supplying 9.8v. I wonder why. So I switch around the SATA connectors and move them all to different ports, check and re-sit all my connections, and I get the same thing. Voltage warning AND the same HDD is not showing up in a different SATA port. So I think: okay, maybe it's a fault with the HDD, causing the PSU to only output 9.8v (I'm an electrical engineer, so I know weird crap like that happens sometimes, so who knows?), so unplug that HDD from power and the SATA port, same voltage warning. I unplug ALL SATA devices, same voltage warning. So I think "okay, it's probably the PSU", so I hop into the BIOS again, and low and behold, the computer restarts on me randomly while I'm in the BIOS sometimes.

So here's the real question:
- Is it the PSU? If so, why is that one specific HDD not showing up no matter what SATA port it's in and my other ones are, even if it's the only SATA device plugged in. It just seems strange. But then again, I am getting occasional random restarts while in the BIOS...
- Is it the HDD? If so, there were none of the usual warning signs. I've had this same issue before, and completely took the computer apart and reseated EVERYTHING short of the CPU and it worked again for months, no problem.
- Is it the mobo? If so, how do I go about knowing for sure? Do I run some diagnostic software on it? There are no blown/bulged capacitors or burnt parts. No red light. Nothing to point to the mobo as the issue.

I just don't know. What do you guys think? I'm going to run some diagnostic software pretty soon here. Before that, I may reset the CMOS and/or try a new PSU.

More about : issue diagnose

a b B Homebuilt system
January 12, 2011 2:10:07 PM

I would try the new PSU first. That one specific HDD may be more sensitive to voltage changes than the others. Are your HDDs all the same make / model? As you said... weird crap!
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January 12, 2011 2:12:32 PM

sadams04 said:
I would try the new PSU first. That one specific HDD may be more sensitive to voltage changes than the others. Are your HDDs all the same make / model? As you said... weird crap!


They're not the same make/model. The one that doesn't show is a 10,000 RPM drive with the OS loaded on it. The other is a 7200 RPM. Obviously, the 10,000 RPM probably draws more current, but I don't know if that's really related or not. And yeah, it is weird.
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Related resources
January 12, 2011 2:19:17 PM

Yeah, I would try a spare PSU if possible. If you have a power supply meter and multimeter and know how to use them (I don't, but I recently had to take my computer to a repair shop, and they used them to test my PSU, which was faulty), you could also probably diagnose your PSU using them.

As for your HD, why not just use some of the Ultimate Boot CD's hard drive diagnosis tools? Also, have you tried a different SATA cable on your HD?
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a b B Homebuilt system
January 12, 2011 2:23:31 PM

It probably is your psu... is the one you are currently using designed with a multi rail or single rail design? The higher rpm drive is probably not getting enough power to run properly and therefore not working. I'd agree with sadams and try a new psu and see if the drive works or plug it into another computer if you have one around and try getting the drive to boot there. If you can read the drive you know it's not it, and it's the psu.
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January 12, 2011 4:45:25 PM

Hastibe said:
Yeah, I would try a spare PSU if possible. If you have a power supply meter and multimeter and know how to use them (I don't, but I recently had to take my computer to a repair shop, and they used them to test my PSU, which was faulty), you could also probably diagnose your PSU using them.

As for your HD, why not just use some of the Ultimate Boot CD's hard drive diagnosis tools? Also, have you tried a different SATA cable on your HD?


I don't have a PSU tester or multimeter (though I SHOULD have a multimeter, I've never needed one at home). I can borrow a spare PSU from work and use that. I can't use the diagnostic tools if the HDD isn't recognized, but thanks for the link. I doubt it's the HDD, though.
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January 12, 2011 4:51:23 PM

evilavatar said:
It probably is your psu... is the one you are currently using designed with a multi rail or single rail design? The higher rpm drive is probably not getting enough power to run properly and therefore not working. I'd agree with sadams and try a new psu and see if the drive works or plug it into another computer if you have one around and try getting the drive to boot there. If you can read the drive you know it's not it, and it's the psu.


Honestly, I don't know if it's multi rail or single rail (though I probably should, shouldn't I? I guess I've never had to know). What difference would it make? I may try using a spare PSU. I'm fairly sure it's not the drive.

HOWEVER, a faulty SATA cable would make a lot of sense (except for the voltage issue). And guess what? I just switched out the cable and it's recognized again and boots. No voltage warning either. What the heck? I really don't know. I'm going to permanently switch out the old SATA cable just in case, to eliminate another variable. It's so strange. The PSU I have in there has been RMA'd and repaired in the past. I didn't mention that because I didn't want it to skew anyone's ideas about what the problem might be. But add that into the equation after we all agree that it's probably the PSU and it makes a lot more sense. I may have to get this PSU replaced if this happens again. I just have no idea.
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January 12, 2011 4:55:34 PM

Right as I post this, I hear in the other room "beep". The friggin computer was booted into Windows and then restarted itself (and no, it wasn't automatic updates. I hadn't signed in yet). It's got to be the PSU or mobo. But then why did switching out the SATA cable make the HDD recognized? Fluke? Or perhaps both a SATA cable and the PSU went out at the same time? Unlikely, but possible. This thing is going to drive me up the wall. Thanks a lot for your help, guys.
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January 12, 2011 5:01:31 PM

I had a similar issue just last week (would power on, then do nothing, except for ONE time when it got to the BIOS screen, but I didn't hit "Delete" fast enough, and then it went into loading Windows and the screen went blank again).

Had it tested out by a computer repair shop and it turned out that the PSU and motherboard had died. Luckily they both had 3 year warranties, so I am RMA-ing both now, *sigh*...
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January 12, 2011 5:12:27 PM

Hastibe said:
I had a similar issue just last week (would power on, then do nothing, except for ONE time when it got to the BIOS screen, but I didn't hit "Delete" fast enough, and then it went into loading Windows and the screen went blank again).

Had it tested out by a computer repair shop and it turned out that the PSU and motherboard had died. Luckily they both had 3 year warranties, so I am RMA-ing both now, *sigh*...


I do not envy you, good sir. That's certainly a worse fate, though perhaps a bit easier to diagnose. So it's kind of a double-edged sword. My computer now seems to be working fine. I just replaced a friggin' SATA cable. That cannot be the issue. I think it would have been fine even if I didn't do that. I remember the first time something similar to this happened, I shut it down for a few hours, then it was fine. This seems to be the case here. Perhaps the PSU is actually bad (it's likely). If this happens again, I will certainly RMA it again and demand a replacement instead of a repair. So sad. It's always the PSU for me...

Thanks again.
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a b B Homebuilt system
January 12, 2011 5:46:42 PM

http://www.directron.com/800w.html check out the psu's here... I'd see if can get a refund than go overboard and put in a psu bigger than I ever think I'll need.
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January 13, 2011 3:39:47 AM

Haha, just heard back from OCZ Technology about my PSU RMA...

"I've checked with our RMA department and your replacement is currently on backorder and so an Advanced Replacement is not possible. I've looked into other models and there is nothing available close to the specs of your unit (OCZ700MXSP and OCZ550FTY)."

...And they won't give me a refund, the bastards... How on earth could they be out of stock on my PSU as well as any comparable model!?!
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a b B Homebuilt system
January 13, 2011 7:55:23 PM

2247066,7,803648 said:
Honestly, I don't know if it's multi rail or single rail (though I probably should, shouldn't I? I guess I've never had to know). What difference would it make? I may try using a spare PSU. I'm fairly sure it's not the drive.

With the single versus multiple rails you can run into an amperage versus wattage issue. If everything is pulling from one rail they are usually designed with a fairly high amperage compacity, but it may not be sufficient to run everything at the same time. With multiple rails you ahve to make sure you have your wires for each item run from the right spots or the connectors might not be getting sufficient amperage and voltage to the parts (this assumes the maker has seperate rails running seperate connector sections which is not always well defined).
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!