Optiplex 9010 Problem

Hello, and thanks in advance for any help.

I have a SFF Optiplex 9010 that had a blank screen, and I killed a second one trying to fix the first.

First one - No BIOS, no Dell splash screen.  Fans were running and power light was white.  Turned off, and removed the hard drive and DVD drive.  Rebooted, no Dell splash screen.  Replaced the RAM, same.  Removed the RAM, beeps and flashing yellow power light.  Replaced the power supply and put the RAM back in, on power up still no Dell splash screen.  Put the hard drive in another Optiplex SFF 9010, it started to boot Windows, then went to auto repair, failed auto repair a few times as I rebooted a few times,  I then ran diagnostics.  After 20 min, it told me the hard drive was bad.  I reinstalled the original hard drive to start to configure the second computer as a replacement for the first.  Now I get a black screen on the second one also.  CMOS battery was replaced, so that's not the problem.  Any thoughts?

Thanks,

John