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Computer Will Not Post

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April 9, 2011 11:52:08 PM

I searched the site and found similar scenarios, but haven't found a solution.

I have an Sony Vaio (rx 550) that has run perfectly for years. About a year ago, I moved and put this machine in a storage unit. Two days ago I got the machine out of storage and attempted to use it and discovered the problem.

The power comes on, fans run continuously, sounds like HD is spinning, but nothing happens. No beep, no signal to monitor, keyboard doesn't have power.

The LED on the front of the machine labeled HDD doesn't light up. The CD drive however does work.

What I've done so far:

Replaced cmos battery
Reseated all components and power connections
Replaced PSU
Removed RAM
Reseated RAM
Tried starting machine without components/cards. (motherboard, PSU, CPU only)
Removed motherboard and inspected very closely for bulging capacitors, signs of damage etc... mobo looks brand new
Kicked machine (not really but i wanted to)

My next step is to take the machine to a professional shop Monday morning, but they are going to charge me a hefty amount to run tests. I was hoping I could glean some useful info from this community and maybe fix the problem myself.

Any ideas?

More about : computer post

April 10, 2011 1:42:54 AM

Resetting the cmos battery should've resolved the hardware configurations lost due to expired battery, but try putting the CMOS jumper to Reset if Sony Vaio has it, turn it on then off after posting, reset jumper to normal and enter config.
Static can be an issue, make sure to plug it into 3 prong outlet.
Was the PSU switch off while in storage ?
You should get beeps for missing RAM or CPU, even missing video card if none onboard. Otherwise it might just be a dead MOBO, shorted by critters or water dmg. while in storage.
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April 10, 2011 7:14:25 PM

Thanks for the reply.

I tried using the jumper reset method described for my mother board (Asus P4B-LX rev 1.04) here: http://www.unitycorp.co.jp/support/download/manual/478/... on page 2.16.

This mother board has two three prong switches with a jumper cap on each of the 2/3 prongs. I tried your method of switching the cap and then powering on the machine but with the jumper cap placed on the first two prongs the machine wouldn't even power up.

I've plugged it into several outlets to be sure there wasn't a problem with the surge protector also.

The original PSU didn't have an on/off switch. The only power switch was on the front of the machine. The new PSU I have now has an on/off switch but when it was stored there is no way there could have been any electricity to the board.

I'm baffled at this point.
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a b à CPUs
April 10, 2011 7:57:39 PM

how many watts is the new and old PSU?
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April 10, 2011 10:54:53 PM

New one is 380, the old one lists 268.9w max output.
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a b à CPUs
April 11, 2011 1:12:55 AM

If you can, try testing the individual parts elsewhere to isolate the MB as the problem. If so, I doubt a shop will give you any useful information.

You can always try baking dead parts. I'm three for three on graphics cards.
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a c 172 à CPUs
April 11, 2011 1:21:35 AM

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%. If you have a white wire (many modern PSU's do not), it should be -5 volts.

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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a b à CPUs
April 11, 2011 1:34:06 AM

Well...that's smarter than throwing parts in an oven!
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April 11, 2011 4:51:34 PM

Took it to a shop today and did more testing with different video cards, memory, unplugging everything but the motherboard, pcu, and the psu.. looks like my fears were confirmed; it's the mobo.

Only problem is this mobo is old as dirt. Anyone know where I can find one cheap? Refurb?

Thanks.
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