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PSU works with other computers but not mine

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a b ) Power supply
October 15, 2010 10:24:29 PM

Hello,

About a year ago, I bought a computer from Best Buy. It was a mistake. 3 months ago, I started having problems of overheating. The model was HP Pavilion e9180f, a computer with very high end components (click on the link for the details).

That is why I decided to change the case and the PSU. By the way, on the website of HP, it says that the PSU has 460W, but on mine, it was written 385W. I opted for the CoolerMaster HAF X and the CoolerMaster Silent Pro Gold 1000W.

The problem is, the computer would not POST, and I had no video signal. I could hear the fans on the case and on the motherboard spin, the HDD and the Optical Drives worked fine. The CPU was working, as well as the graphics card. I simply had no video signal on my monitor. I also remarked that when I was powering on the computer, everything would start, then after 5 seconds it would all shutdown, to restart only 3 seconds after that. I timed it and it was always the same. It would only do that when I disconnected the power cord from the wall. When it does that, I realized (by plugging my old PSU) that the BIOS was always reseted.

I’m not new to building computers, so I immediately checked all my connections and etc. Everything was ok. I put in my old PSU, and the computer worked fine.

By a process of elimination, I was able to determine that the problem came from the 24-pin ATX connector on the motherboard. I then tested the voltage on each pin, as well as all the grounds (COM), with a multimeter. It was all within the norms, even the Power Ok (or Power Good).
I then used a PSU tester to check the time it took for the power to stabilize and the 5V value to be displayed by my power supply. The result: between 340 and 360 milliseconds, so there was no problem on that side.

I then used the PSU tester on my old power supply, and again, the results were the same as before, to a difference of 0.1V. The only “major” change was that the PG signal was much more stable, it was always at 350ms.

After that, I chose to test my PSU in other computers. I tried it with a 20-pin and 24-pin ATX motherboard, with or without a pci and pci-e graphics card, a multi-core and single-core CPU, with DDR1-2 RAM filled or half-filled. In all those cases, the computer booted and worked as supposed to.

I tried to test a friend’s PSU on my machine, and it worked fine (it was an Antec 550W). I used my old PSU to power only my motherboard, and the new one (with the pins 15 and 16 shorted) on all the other components, and the computer booted.

I’ve now tried everything I know, to no avail. That is why I’m asking for your help. I am now left with only three hypotheses:
1.My new PSU is not compatible with my motherboard.
2.My motherboard cannot use a PSU of more than 600W or so.
3.The PSU is defective, and cannot provide enough power (through its 24 pin connector) to a motherboard that needs a lot of juice to boot (as is the case with an X58 motherboard). That would explain why it worked with a less powerful computer.

That is all I could come up with. Any ideas as to why it does not work or, even better, solutions to my problem, would be greatly appreciated. My next step would be to ask for a RMA and request a new one, without the assurance that this new one, be it the same or an other model, will work.

Thank you for your help,
al360ex
a c 713 ) Power supply
October 15, 2010 10:32:13 PM

1 unheard of
2 it should run even if you had 2000watt PSU
3 most likely the case
I would try to get an Antec, corsair or seasonic even XFX instead.
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a c 243 ) Power supply
October 15, 2010 10:39:07 PM

rolli59 said:
1 unheard of

Just one example, read the yellow box at the bottom
http://www.silentpcreview.com/article273-page5.html
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a c 713 ) Power supply
October 16, 2010 12:47:47 AM

delluser1 said:
Just one example, read the yellow box at the bottom
http://www.silentpcreview.com/article273-page5.html

That is really strange! All it does is put out volts DC within ATX specs but then again there might be something wrong (different) with the power OK signal for some motherboards.
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a c 144 ) Power supply
October 16, 2010 5:22:33 AM

al360ex said:

The problem is, the computer would not POST, and I had no video signal. I could hear the fans on the case and on the motherboard spin, the HDD and the Optical Drives worked fine. The CPU was working, as well as the graphics card. I simply had no video signal on my monitor.

If it is not posting, it is not working.

The PowerOK signal is a simple TTL Logic HIGH signal. When active, it removes a hardware reset signal from the CPU. If another PSU works, I don't see how it could be the problem.

Start over.

Work 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.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

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.

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...

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.

This will be a little different if you have integrated graphics.

Silence or long single beeps indicate a problem with the memory.

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.

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 ) Power supply
October 16, 2010 6:56:34 PM

jsc said:
If it is not posting, it is not working.


Then how do you explain that, without touching or replacing anything else, simply using another PSU (like my old one) will solve the problem ? And how does it explain that my new PSU works with other, less powerful builds ?

Thank you for your very comlete answer, but I had already done all of those steps before starting this thread. Also, because my motherboard is an OEM, there are no place to plug a speaker into, and I have no instruction manual either.
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a b ) Power supply
November 27, 2010 3:25:07 AM

Best answer selected by al360ex.
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a b ) Power supply
November 27, 2010 8:14:46 AM

This topic has been closed by Maziar
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