MP 1,1-5,1 Mac Pro 4,1 problems No screen/no chime

[Eise]

Recently I bought 2 Mac Pro 4,1s. They are both dual socket, when I powered the first one on it booted after a few tries. When I tried to boot up the second Mac Pro it didn''t boot up. Black screen and no chime, after trying swapping parts with the other mac pro they both do not work anymore. I tried everything I know. Different RAM, no RAM, one CPU, swapping Cpus, swapping gpus, no hdds, no odd, PRAM, SMC reset. I bought them really cheap but still hope they are not completely broken. The G5 that was also included works perfectly, that feels a bit frustrating.
One of them has a RAID card and a 4870 mac edition and a RAID card. The other one has a GTX 680 EVGA mac edition gpu.
Both have 2 2,66GHz qc cpus and 16GB of RAM.

Anyone got some ideas I can try?

 

[Macschrauber]

as they were 2,66 - both have cpus without Heatspreader (lidless?)

mac #1 what powered on after a few tries could have a psu what was faulty.

mac #2 could have a dead psu.

if youre in bad luck you have killed parts with this unstable psu of #1

just had a guy in the same boat posting about killing his cpu board with swapping around machines with a unstable psu involved.