It is sometimes useful — for reasons hitherto unexplained — to leave a CC plugged in, and with the rear power switch turned on, for 24 hrs or so and then try to boot it. It somehow "wakes up," sometimes.

It is, of course, also possible that the machine is toast, or that the capacitors have failed (not getting anywhere being a typical symptom), but I would try the first alternative first. It used to be a standard piece of advice around here.