No power after ambient sensor install

National Grid fried my Mac Pro (2007) a few years ago. I replaced it with a Mac Pro 2008 and later added a Mac Pro 2010.

The original Mac Pro at the time would boot, but kept shutting down randomly. I couldn’t get it to stop it , despite experience at fixing and writing about Macs. Once I replaced it, I just stored it for several years. When I got it out of storage recently, I decided again to try to fix it.

Since the fans came on high from booting, I finally started thinking that the power surge fried the ambient temperature sensor rather than something more serious. So, I bought one, followed all normal procedures to install it, put the computer back together.

I then plugged it in and heard this ominous by faint pop and sizzle from the power plug. Now, it gets no power whatsoever and won’t startup to chime as it did before I replaced the sensor.

Any ideas at all would be helpful.

Did I do something obviously wrong with my install? Is it the power supply, as I originally thought? Is it the logic board and therefore not worth fixing? Is it something I haven’t thought of?

Thank you.

Shawn