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Motherboard won't turn on after installing new PSU

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  • Homebuilt
  • Gigabyte
  • Motherboards
  • Systems
Last response: in Systems
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November 22, 2011 3:42:31 PM

Hello,

I'm running a stock C2D Q6600 w Gigabyte GA-P35-DS3 mobo. I recently bought a OCZ ModXstream 700W PSU to replace my old Antec 500 because I couldn't OC with it. After I replaced the PSU and plugged in all the cables, the computer won't turn on at all, as if it's not getting any power.

Then I plugged in my old Antec PSU (only 24pin plug and 12V plug) to check, the MOBO still won't light up.

For further testing, I found a old satek mobo laying around. I wired the case power and reset botton onto it, then plug in only the 24pin plug and 12V plug OCZ psu while leaving the rest of the cables connected in my GA-p35-Ds3). After firing it up. The old Satek mobo turned on, along with all the fans and lights on the Gigabyte board. My conclusion from the test is that the new PSU is working, the chasis's power bottons are wired correctly, and the Gigabyte Mobo still somewhat function. So is the power distribution on the Gigabyte gone bad? Is there any other test I could run before deciding the mobo has gone bad?

A side note, when I was plugging the 24pin plug onto the Gigabyte mobo, the CPU cooler did light up for a brief second. And the weird part is that the main power switch behind the PSU was off??

More about : motherboard turn installing psu

a b B Homebuilt system
a c 231 V Motherboard
November 22, 2011 3:59:24 PM

Sounds like you may have damaged your mobo (potentially) when you swapped the PSUs. Verify that you have firmly connected both the 24-pin and 4 or 8 pin aux power connectors (firmly click into place) and try again.
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November 22, 2011 4:23:35 PM

An explanation for the side note is: a capacitor in the PSU discharged.
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November 22, 2011 5:11:00 PM

Thx for the fast response. I tried with both PSUs before w no luck, but i'll take everything off and try just with the psu and the board w cpu.

But before I invest into another mobo, how could I've potentially damage the board? I unplug the main power before disconnecting any cables and I kept the main switch off until everything on the new psu got plugged in. very straight forward and im pretty sure I kept one hand grounded to the case the whole time.
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a b B Homebuilt system
a c 231 V Motherboard
November 22, 2011 5:15:47 PM

Static discharge is always an issue. You should also press the power button (after disconnecting all power sources; e.g., power cable, monitor/video, powered speakers, etc) to discharge residual power stored in the various components in your system BEFORE you start taking stuff apart. Strange, but true.
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November 23, 2011 2:40:27 AM

Ok, quick update. I took the Mobo out of box and disconnected everything except for the F_panel leds. Hooked multiple PSUs (all certified to work on a seperate Mobo). When only the 24pin plug was plugged in, everything would start w/o a hitch (judging by the CPU cooler. But right after I plug in the 4 pin 12V pin (combined w 24pin plug), the CPU cooler would try to start for a second and then nothing, the fan on the PSU would still spin. Any thoughts on this symptom? I guess this Mobo is still F'ed in the A?
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November 23, 2011 7:03:06 AM

Manoftheyear2k said:
Ok, quick update. I took the Mobo out of box and disconnected everything except for the F_panel leds. Hooked multiple PSUs (all certified to work on a seperate Mobo). When only the 24pin plug was plugged in, everything would start w/o a hitch (judging by the CPU cooler. But right after I plug in the 4 pin 12V pin (combined w 24pin plug), the CPU cooler would try to start for a second and then nothing, the fan on the PSU would still spin. Any thoughts on this symptom? I guess this Mobo is still F'ed in the A?


The colors of the CPU's 4-pin 12V cable are yellow and black.
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November 23, 2011 10:54:11 AM

that's correct. and when I plug it in along with the 24 pin plug, the cpu cooler would have trouble starting up.
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a b B Homebuilt system
a c 231 V Motherboard
November 23, 2011 2:20:00 PM

Sounds like a fried mobo at this point. Sorry.
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December 6, 2011 12:39:17 PM

A new update on this. I ordered a new GA-Z68XP-UD3 Mobo from Newegg. Wired everything up w the OCZ Modxstream 700W and..... NOTHING! Also tried with other power supplies and still nothing turns on. So I thought, ok, a new DOA board, it happens. So then I re-wired up my MSI H61 mATX board, which I was using while waiting on the new board to arrive, to the new OCZ PSU. but now, the CPU fan would only turn on for 2 seconds before shutting down, then everything goes dead. I tried with other working PSUs and same symptom.

Now i'm suspecting maybe it's the OCZ PSU killing all my boards, since both old and new Gigabyte mobo won't work after I plugged in the OCZ. However, i'm confused because the MSI was working before with the OCZ PSU, but now it's not. I also tested out the OCZ PSU with the ancient Saitek mobo and still worked. Any opinions? Could a new PSUs kill mobo like this? Can I RMA the OCZ PSU? but on what ground since it's still working with certain boards?
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December 6, 2011 4:22:13 PM

You can test the PSU with a multimeter and a paper clip to determine if it's putting out the right voltages. I've seen power supplies that turn on but only put out half the required voltage. Disconnect all the power connections from the OCZ PSU. Plug in some old drives or something, CD/DVD/floppies whatever. Don't plug in any of the motherboard connectors. Take the paper clip and bend it into a U shape and insert one leg into the SOLID GREEN WIRE ON THE 24 PIN MOTHERBOARD CONNECTOR. Insert the other leg into ANY BLACK WIRE ON THE 24 PIN CONNECTOR. The power supply should switch on. Use your multimeter to test.

You should get:

SOLID RED to SOLID BLACK (ground): +5V
SOLID YELLOW to SOLID BLACK (ground): +12V
ORANGE to SOLID BLACK (ground): +3.3V

Remove the paper clip to turn off the power supply.
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a b B Homebuilt system
a c 231 V Motherboard
December 6, 2011 4:36:27 PM

Also, verify that the 4/8 pin aux power connector and the 24 pin main power connector are firmly attached (push until the retaining tab clicks into place) to the motherboard connectors.
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December 7, 2011 11:56:02 AM

The OCZ PSU passed the voltage test, per Nuts' instruction. So does that mean the psu is good and it's just bad luck that all 3 of my mobo failed to boot? I'm getting the new mobo s RMA'd. I just don't want them to go bad again because of the psu
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a b B Homebuilt system
a c 231 V Motherboard
December 7, 2011 1:12:29 PM

When you look at the common variable in the equation, your PSU does become suspect especially when you consider more than one mobo has been involved.
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