Hi [NAME], You posted in the Optiplex forum.  Dell Precision Fixed Workstation is here.  I can still answer though.  Try the BIST test.  I couldn't find a BIST video for your T1500, so an Optiplex one will have to do for an example.  As for testing various components, it's the same difference.  [URL] Please let us know how it goes.
The power supply works fine, tried the paper clip test. there's no mobo light, button cords seem fine. there have been mice into it recently, had to clean that. its been off for a few days bc of a power outage, which right as the power shut off, I shut off the surge cord before it got the chance to turn on again, or surge. so whats the issue? the mobo looks fine to me. any tests?
dell precision t1500 not turning on