No Chime , Black screen.

Mac Pro 2006 Quad core 2.66 GHz

I have gone through many steps of fixing this, but all in vain.

When I switch on my machine the CPU & GPU fans power on. No Chime/Bong is heard. Screen remains black.

I have tried all methods of doing SMC reset & PRAM reset. I had noticed that my PRAM battery had died. So I replaced it with a new one. But! Still the same problem.

The Diagnostics lights on the mother board show the trickle power as yellow, PWRG on is Green and GPU is green, EFI remains Off.

I tried connecting the keyboard and resetting PRAM as it worked for somebody but in my case it's not working.

Holding the power button for firmware restoration doesn't work as it does not start blinking. it just remains solid white.

Also useful to know. I wanted to upgrade this system to 2,1 so I tried to upgrade the firmware but that did not work although it did follow all the steps (was trying this using USB and pressing power button as stated in netkas procedure) .

Anyhow I upgraded the OS to El Capitan by just changing the Boot EFI. it worked properly for few days until this happened.)

Basically the system is a stock 1,1 with OS-X El Capitan.

I have read through many forums to try to make this work but still not able to solve it..

Please suggest something so I can get this back to life.

Extremely urgent! Thanks

Link to what happens when I start: No Chime , Black screen.