Question PSU woes - A jumpered PSU won't start

[RisingFish]

I bought a new Seasonic Prime PSU last week because my old PSU's fan was getting loud, and it was going to take a couple weeks to warranty it (I use this PC for work occasionally so needed it up sooner). I'm an experienced PC builder and installed it yesterday. When I pushed the PC power button nothing happened. I then unhooked everything, removed the PSU from the case (everything was unhooked), jumpered the start pins, and it still wouldn't turn on. I pulled out my DMM and verified the AC power code was showing 120v plugged in. Then I tested a few pins in the 24 pin motherboard connector and found that not all of them appeared to be powered up. I found only one 5v pin and one 12v working (I very well might not be doing this right, but I know enough about basic electronics to keep one of the DMM leads on a common pin). I tried it with both hybrid mode off and on.

To compare, I then hooked up the old PSU (EVGA SuperNOVA G2) and tried powering on the the PC, and again nothing happened. I took the old PSU back out and tried jumpering the 'on' pins and the the old PSU won't start now. I have never run into this issue before, so I'm not sure where to go from here. Is it possible the motherboard is bad and frying the PSU's now?

 

[DSzymborski]

I bought a new Seasonic Prime PSU last week because my old PSU's fan was getting loud, and it was going to take a couple weeks to warranty it (I use this PC for work occasionally so needed it up sooner). I'm an experienced PC builder and installed it yesterday. When I pushed the PC power button nothing happened. I then unhooked everything, removed the PSU from the case (everything was unhooked), jumpered the start pins, and it still wouldn't turn on. I pulled out my DMM and verified the AC power code was showing 120v plugged in. Then I tested a few pins in the 24 pin motherboard connector and found that not all of them appeared to be powered up. I found only one 5v pin and one 12v working (I very well might not be doing this right, but I know enough about basic electronics to keep one of the DMM leads on a common pin). I tried it with both hybrid mode off and on.

To compare, I then hooked up the old PSU (EVGA SuperNOVA G2) and tried powering on the the PC, and again nothing happened. I took the old PSU back out and tried jumpering the 'on' pins and the the old PSU won't start now. I have never run into this issue before, so I'm not sure where to go from here. Is it possible the motherboard is bad and frying the PSU's now?

I assume you did not re-use modular cables, correct?

Assuming you did not, it might be time to just drag it out of the case and breadboard it as if it were an uncooperative build.

 

[faalin]

I find it kinda of hard to believe that 3 PSU wont jumper on.

with the release latch pointing up you should be jumping pins 4 & 5 on the top row counting from the left.

 

[RisingFish]

I assume you did not re-use modular cables, correct?

Assuming you did not, it might be time to just drag it out of the case and breadboard it as if it were an uncooperative build.

Yeah, none of the modular cables were plugged in, only the motherboard cable was hooked up. I also used the modular cables specific to the PSU, and didn't reuse. I like the breadboard idea. Do PSU's have internal fuses or breakers by any chance?

 

[DSzymborski]

Yeah, none of the modular cables were plugged in, only the motherboard cable was hooked up. I also used the modular cables specific to the PSU, and didn't reuse. I like the breadboard idea. Do PSU's have internal fuses or breakers by any chance?

Good, just making sure. Lots of people assume pinouts are universal on the PSU side, to very disastrous results!

There's nothing easily user-serviceable here. Let's tackle one problem at a time!

 

[RisingFish]

I find it kinda of hard to believe that 3 PSU wont jumper on.

with the release latch pointing up you should be jumping pins 4 & 5 on the top row counting from the left.

Yes, those are the two pins I am jumpering (pins 4 and 5). The Seasonic came with a jumper attachment that I also tried (though it jumper pins 3 and 4, pin 3 is also common like pin 5). The only commonality between the two is they were both plugged into the motherboard before I took them out and tried to jumper them.

I agree that it's weird that these 2 PSU's won't start when jumpered. I'm about to take a part an PC I use as a server and pull the PSU out to see if I can jumper that one. I know it works right now.

 

[RisingFish]

So, to wrap this up. I never figured out exactly what is going on with the old PSU. I still can't jump start it and the Seasonic was sent back for a refund. I did discover the BestBuy sells components , which I knew years ago but forgot, and picked up a Corsair PSU there last night. I was shocked by the price though, they're actually selling stuff for MSRP instead of double or triple that. The first thing I did when I got it home was jump start it and it works fine. I then put it in the PC, hooked everything up, and it's working fine as well.

 

[DSzymborski]

So, to wrap this up. I never figured out exactly what is going on with the old PSU. I still can't jump start it and the Seasonic was sent back for a refund. I did discover the BestBuy sells components , which I knew years ago but forgot, and picked up a Corsair PSU there last night. I was shocked by the price though, they're actually selling stuff for MSRP instead of double or triple that. The first thing I did when I got it home was jump start it and it works fine. I then put it in the PC, hooked everything up, and it's working fine as well.

It's quite possible you just had really awful luck with PSUs before! It's definitely lousy luck to run into these problems with two truly excellent PSUs.