Ok, this is the thread that hurts to post more than any other I've ever put here - my dual-tray X5690 Mac Pro 2009 (upgraded to 5,1 firmware) today has decided its all done powering up like normal. I've done lots and lots over the years since I bought this one new so I'm quite familiar with all the usual tech details and gotchas on these, but it IS the only Mac Pro I've ever owned so I'm hoping some of you out there that go thru bunches of these might have some ideas on what I try next. So normally my Pro specs/details look like this: - (2) X5690's on a dual tray. I bought the dual tray predone from a fellow on ebay 3 or 4 months ago who does lots and lots of these - I didn't trust doing the X5690 upgrade myself on a 2009, and I was using the original single-tray with a W3690 I had upgraded it too years ago before this. The dual-tray temps and CPUs have been working great so far up to this current problem today - (4) 3.5" drives in the drive sleds, 1 optical drive, and 3 SSD's internally - Sonnet Tempo Pro Plus in slot 4 using 2 840 EVOs - Caldigit FAST eSATA/USB3 Pro card in slot 3 running 3 of the SSDs - Slot 2 empty - Slot 1 - GTX Titan (original) powered by a X5 booster in the second optical bay So today I decided at long last that I was gonna pull the Titan and use it in a different system, and replace it in the Mac Pro with a GTX 970 (unflashed) and finally get rid of the auxilary power supply and go back to just standard power. I shut it down and make the swap but when all the cables were hooked back up it now gives no chime at all or seems to even attempt to boot. Things I've tried so far: - SMC resets (can't do any PRAM resets right now since I get no chime nor does it get to the point of even initializing USB and any keyboard connected) - Pulled ALL hard drives, cards, etc. Took it back to just the optical drive and a single EFI standard Mac Pro video card - still the same results - Put the Titan and aux PS back in to see if that still worked - it didn't of course - same no chime - Pulled and reseated the ram and the dual-tray itself - no change - There are no red lights at all on the tray and I certainly haven't been messing with the heatsinks on it - doesn't seem like any issue there - When I try to power it up, the white power LED on the front does come on, and even stranger all the fans start up just as you would expect - I can check all of them and the PS, PCI, intake/exhaust and both booster fans are all running at nice slow standard RPMs - just no video, no chime and no boot Anyone with more experience that me have any ideas on what I can try here? Does this sound like my power supply itself or something else? Ive not ever tried anything I *know* to be dangerous like running a card like the Titan without external power so I can't see what I would have done that fried anything (and there's no smell or other indication of that) - it just doesn't boot any longer.