There is also this to consider: Posted about the same time as the original poster... Sorry Folks, iPhone 7 Home Buttons Aren’t User Replaceable WRITTEN BY JULIA BLUFF Bad news for the DIY-inclined: looks like the home button in an iPhone 7 or 7 Plus can’t be replaced with a different one. If you break the button or rip the cable, you’ll have to go to the folks at the Genius Bar for a repair—or be stuck with a completely non-functioning home button. .... The iPhone 7 and 7 Plus appears to take this feature a step further. Home button replacement—or damage to the original home button cable—renders the button completely non-functional: no Touch ID and (here’s the new part) no return-to-menu ability. You can still navigate your phone by turning on Assistive Touch. But for all practical purposes, you’ve got a dead home button. One that you can’t fix on your own or at an independent repair shop. ~~ Read the rest here: https://ifixit.org/blog/9020/no-fix-iphone-7-home-button/

Thanks for the help, but after I posted that I did a little more digging. Turns out that the video card tries to power up when the machine gets plugged in, and every time I plugged it in, I let a little more of the magic smoke out. I used my eyes to trace where the smoke was coming from, and sure enough I found some blown ICs on the graphics card. Put another card in and viola! IT WORKS!!!! Something in the short circuit on the GPU card must have been dragging the power supply down or something… Thanks for the help, but it was not the power supply! What an odd one!