Help! 2 out of 3 PSU won't start

[dloganbill]

I have three brand new PSU with an AsRock Pro BTC MB, but only one will boot the PC.
850W Corsair RM850
1050W Seasonic SS-1050XM
1300W EVGA 1300 G2

I started out originally mining with the 850 and 1050 with 4 R9 290s.  I realized I was working the PSUs too hard so I decided to replace the 850 with a 1300.  It was backordered, so a week goes by and Amazon finally got it to my door.  I shut the rig down, swapped out the small 850, and tried to reboot.  Nothing happened.  The CPU fan twitches and that's it.  I could hear a single "click" sound in the PSU.  I then started from scratch breadboard style (just the 1300 PSU, MB, and CPU).  Still nothing. Then I tried just the 1050W PSU and still nothing.  Same problem with the 850.  I jumped the power on pins and tested both of them.  The 1300 was dead and the 1050 had 12.75V on the 12V pins.  The 850 tested fine.  I don't have a MB speaker so it's hard to know what exactly is going on.  So I sent the 1300 and 1050 off on RMA.  While I was waiting on them to show back up, I replaced the MB and CPU and that got the 850 to boot up and running two GPUs.  Now I have both of the new PSUs back and I'm having the same problem.  I can run the 850 fine solo, but adding either of the larger power supplies will not boot.  Connecting either the 1050 or 1300 solo will not boot either.

I'm getting pretty frustrated and would really appreciate any advice.
If it makes any difference, here is a full build list:
https://bitcointalk.org/index.php?topic=472247.msg5213152#msg5213152

[dloganbill]

Bump.  Any advice?  It is probably something small and stupid I'm missing because I have a hard time believing that these power supplies are duds.  They just showed up from factory.

What I don't understand is why the 850 will boot the system solo, but none of the others will power up.  I have not "jumped" the power supplies again.  When I was on the phone with Seasonic tech support, they said that would cause damage to the PSU.  I could be wrong, but I have a hard time believing that. 

Any advice would be greatly appreciated.

[Wipeout2097]

Make sure there isn't something that triggers the PSU's Over Current Protection (OCP), or a short circuit.

Also, could be something wrong with your mains power. Do you have an UPS? Do you have a voltmeter that can measure up to 250V AC?

When you power on, what precisely do you have connected? Just motherboard, CPU, RAM? Or a Radeon too, some usb adapter, HD, etc...

You may have screwed up something with dual-PSU, two different kinds of risers, and some connection error  

[dloganbill]

Thanks for your help. I have tried them each with just the single PSU, MB, CPU, and RAM installed. Only the 850 will boot to uefi. As far as shorts go, what should I look for? The MB is screwed to wood with plastic tubing for stand offs. The RAM is good since it runs 100% with just the 850. It is not plugged into a UPS but if there were a mains problem, wouldn't the 850 drop out too?