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Help diagnosing PSU problem

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July 5, 2011 4:13:08 PM

Hi, I'm having trouble with a PSU and hoping to get some on advice on what might be going wrong.

I recently replaced all the major parts in my Dell 630i, the new build being as follows:

Intel Core i5 2500 3.3GHz
Intel DP67BG Extreme Series iP67
EVGA GeForce GTX 560 Ti
Corsair Memory DDR3 RAM (2x4GB)
750GB (7200 RPM) Hard Drive
Corsair TX650 V2 PSU


The trouble has been (as far as I can determine) with the PSU.

When I tried the Corsair TX650 all the fans spun, lights lit up on the motherboard (none to suggest a problem) but the monitor remained blank. There were no error beeps of any kind. I tried swapping out RAM modules and the graphics card, but still nothing. I then removed all the major components leaving just the CPU and Heatsink on the motherboard, but still failed to boot with no error beeps. I then swapped out the Corsair TX650 for the stock power supply that came with my Dell PC and it sprung to life giving a series of beeps. Once I added back in everything back in it's been working fine. I've reinstalled windows and its been going it without issue.

All this to me suggests it was a duff power supply.

However, to be sure I hooked it up with the components left over from the Dell machine. Again, just connecting up the CPU and heatsink to the motherboard and gave it a whirl (this was setup outside the case on an insulated surface). Much to my suprise it booted giving a POST error beep (as you'd expect). I added in the old graphics card and a stick of RAM, connected up a monitor and it began POST, listing all the components that were missing. There was nothing to suggest the PSU had a fault.

So, does anyone have any idea what the hell is wrong? I want to make sure it is faulty for sure before submitting for an RMA so I know I'm not sending back a perfectly unit.

Any help or advice would be greatly appreciated.

More about : diagnosing psu problem

a b ) Power supply
July 5, 2011 8:41:57 PM

Is there any chance you forgot to plug in the cpu power connector on the first build?
July 5, 2011 9:02:33 PM

I doubt it. I did check all the connections a number of times. At one point I did purposefully boot without the CPU connector. It booted, but automatically shut down. That didn't happen any other time.
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a b ) Power supply
July 5, 2011 10:18:15 PM

There goes the easy answer.
I'm assuming the new board uses 8 pin cpu power and you had both 4 pins plugged in

and the old board uses a single 4 pin cpu power.

Can you try booting the old board using the other 4 pin cpu power? I wonder if one of them is mis-wired.

or assuming your old PSU only has one 4pin cpu power that maybe something is shorting out on the second motherbd socket? I doubt it but might be worth a peek under if its not inconvenient.
a c 144 ) Power supply
July 6, 2011 1:50:21 AM

Stupid question: do you have the system speaker installed in the new mother board?

The problem may not be the PSU.

popatim, the i5's should run quite satisfactorily with a 4 pin CPU power plug.

Time to breadboard the new system. I would have done that before the new components into the case.

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%.

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.
July 12, 2011 4:24:01 PM

Sorry for the late reply JSC. I thought I had set it up to email when someone responded to the thread so I didn't check manually. Thanks for the detailed reply, but I ended up taking my chances and returning the PSU. It was tested and reported to be indeed faulty. Money refunded.

The new motherboard did have a speaker and works fine. As said in the first post, when I plugged in the old PSU it started with a series of beeps. Up until that point I thought there was chance the speaker simply wasn't working. But that clearly wasn't the case.

I also went through the troubleshooting thread to, "breadboarded" the system, etc. I didn't test the power supply using a DMM; I didn't feel competent enough to be sticking paper clips in electrical sockets. I'm accident prone as it is.

Thanks again.
!