mac pro 2009 start

Hi everyone,

My Mac Pro early 2009 won't start. Mac Pro early 2009, 8 core, Intel Xeon. 4 hard drives. Radeon video card 4870 512MB. Memory : 14GB

I've changed the power supply with a new one, cleaned all the dust, unplugged the Radeon video card, the fans, the processor tray, the DVD drive. Reinstalled everything.Replaced the battery button.

After a while, it started, not right from the first attempt.

I've plugged all the 4 disks, keyboard and display.

Mac OS Yosemite check everything and said the memory is not set correctly : one of 4Gb Dimm was not in the right slot and one isn't found. I shutdown. I tried another memory configuration and restarted. Another memory warning appeared about the slots. I shutdowned, remove my 4Gb dimm and started again with 6x1Gb memory set. The computer started perfectly well and ran for 1hour.

Then it shutdowned without notice. The inside was very hot.

I let the Mac Pro cool down with a fan nearby.

Then all the attempts to restart it failed.

I took all the parts away again and tried to analyse the problem. While pressing on the motherboard button an orange led shown, just one : 3v stby

When I plug the power supply to the motherboard, a red light shown for one second near the power button.

The motherboard is 2 years old, already replaced since I've bought the computer. I noticed 2 rusted (silver colored) square components in the middle of the motherboard.

I live in a tropical island, the air is warm and humid. No air con. No Apple store within 3.000km 🙂

Who can help me found how to fix this issue ? Thanks for your time !