If the power strip test does not find the problem: I would with power supply cold & no cover and not starting use a heat gun to see if heating different components will start it. TechTopics 20 has a schematic of a A2000 power supply but with Amiga it might not be for the one you have. I have had the thermal start up resistors ( not Amiga ) to cause intermittent start up problems. (THR! or THR2 on A2000).
http://www.bombjack.org/commodore/commodore/TechTopics_20.pdf
