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I'm hoping there are some PC builders here that might be able to help me on this one. I recently rebuilt/upgraded my workstation after the previous mobo failed with a new ASUS P5Q SE PLUS, a Core 2 Duo E8500, WD VelociRaptor and WIN7. I kept my existing SeaSonic S12-380 380W ATX12V power supply and 3 Gigs of Corsair XMS2 memory. It's been running fine 24/7 for four weeks (built at beginning of July). Today it was sitting locked out with the login screen when  all of a sudden it shut down. Attempts to restart it didn't work from the button and only after I unplugged it and plugged it back in did it try to start. The RAM sticks have LED indicators on them like the level meters on an amplifier and they were going wacky, skipping rows, etc and after a few seconds they'd shut off as though some safety had kicked in.

It wouldn't boot at all after the shutdown and since I don't have parts to swap the mobo, PSU or GFX card, I took it in for diagnosis. do these symptoms ring any bells for anyone here? What should I be expecting to hear from the techs?

i don't know what video card do you have, but that power supply doesn't look big enough..

does it beeps with an error code while booting? [anything except a short beep is an error]

things to try
- clear the CMOS [there's usually a jumper or a button near the battery]
- unplug EVERYTHING, leave just the processor and a stick of RAM. It has to boot and beep a "video error" [beep codes]. If it works start pluging in one thing at the time and see what is the cause.
- check that the power supply is well connected to the motherboard [both cables, the 24 wires one and the 6 wires one]

Finally, a question I can definitely answer.

If you don't see any burn marks or smell any magic smoke it's a good start!

First I'd try re-seating all the easy connections (Power, HDD, memory, but not the CPU). Sometimes it's just something loose. While you're in there look for any stray screws or debris that could cause a short. I always lift up the case and give it a shake and check the back of the motherboard with a good flashlight if I can get to it without major surgery.

Next I'd test the power supply, (be very careful). You can short pin 14 to ground (any black wire) to turn on the supply when it's detached from everything else. First listen for the power supply fan, if that's not on then either it didn't work or the supply's dead. I've attached the pinout for the basic ATX 20 pin connector below, the optional connector uses the same color codes. Basically you're just looking for roughly the right voltages where they should be. I've only seen a half dead power supply once (no 12V) but it can happen. There's a pwr_ok line that should handle voltage checks, but it can fail too, and it doesn't always cover all the rails. If you're uncomfortable tinkering with the supply then feel free to skip it, it's totally understandable.

From here it's all about isolating parts. If you can borrow someone else's machine that'll allow you to swap parts out to confirm they're good. If you have no other option you can try unplugging everything from the power supply but the motherboard just to see if you can get it started. Even pulling the video card and starting the computer without it should get you a post code, assuming you have a speaker hooked up. Check the manual if you have it (if not you can probably download it) for details on post error codes. Any 8? 0.25W or so speaker can be used, so you can 'borrow' one from elsewhere if you need. Some (should be all!) manufacturers splurge on an onboard beeper to save you the trouble.

Hope that helps some :)

Edit: Found this in a newegg review. I've seen it before, and it's probably worth checking.

--- Quote from: Newegg Review ---Hey all, I think I may have stumbled upon an issue which seems to affect pci boards from various manufacturers including asus.

Basic Symptom: a blank display screen, after powering up machine - regardless of being completely off (prior), or in sleep mode/state. Progressively occurring more often over time.

Possible Solution: unscrew the metal pci slot bracket (preattached to all videocards); *gently & firmly* installing the card back into place (motherboard); connect monitor; power system on/off until satisfied with results.

Contributing factors seem to be: insufficient 'cumulative' height (horizontal view on table) of a motherboard's circuit board, and or plastic pci input slots used on motherboards; and least likely - radical case design interfering with sitting height of the pci cards.
--- End quote ---

To clarify a bit, the tolerances are sloppy between case frame and pci slot heights in just about everything. If it's a lot of work to tighten down the GPU then unscrew the bracket and the socket screws so it moves loosely, snap the card in, and tighten everything back up. This removes the unnecessary pressure in the system, hopefully avoiding connection problems.

I went back to the newegg reviews and yep, lots of dead ones out there. Normally I'd sit and try and figure this out myself, but life's a little more hectic with a 2 year old in the house and a business to run :) Worst of all, I don't have spare parts to swap out on this machine. It's probably going to cost me a fortune just to get the diagnosis from the repair guy, but I really don't have the time to deal with it :(.

I don't have a speaker hooked up, so can't say whether the beeps are right or not. The PSU tested ok by the tech with one of those PSU testers. Of course, that doesn't tell me if it's functioning properly under load, but at least it's a start. My GFX card is a FireGL V3300, so not very power hungry. I haven't hooked up all of the peripherals yet, so it should have been fine with what load was on it. Now that I've had some time to do some reading, it's sounding like the board is dead. Should be fun getting that replaced... :(

Thanks for your answers!

I suspect your power supply is operating at its margins and I'd recommend you buy a new one. I'm using a corsair HX650W

This power supply has a 7 year warranty that Corsair stands behind 100%. The one I have installed is a new replacement (replaced under warranty) for my previous HX620W (5 year warranty) which stopped working after 3 year of use. Cost me £40 to send back to Corsair in Holland and a week and a half later a brand new supply arrived. They sent me the newer 650w model with a longer warranty as well. Great company and products.


P.S Some ebay links




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