MP 1,1-5,1 Mac Pro1,1 and 3,1 went dead after complete boot up

[eoegbero]

Hi, I have Mac Pro1,1 and 3,1. with El Capitan running on them. The issue with them is similar in that when the systems were running, they shut off suddenly and they were found to dead when I tried to power on again. The power LED on the the front does not come on when the power button is pressed. I will appreciate if anyone can assist.

 

[Bigwaff]

Check the CMOS/PRAM battery on the motherboards.

 

[eoegbero]

I replaced the CMOS battery with a new one but the System is still dead

 

[splifingate]

they shut off suddenly and they were found to dead when I tried to power on again

At the same time?