Cannot Turn on MacBook Pro

I have the same issue with my 2008 macbook pro a1260. I've replaced the adapter - no luck. shorting the power jumpers on the logic board doesn't power it up. Tested the voltage on the adapter = good. tested the volts where the magsafe port connects to the i/o board (the pins) = ok. but it won't do a thing. I'd hate to replace the i/o board when it's the logic board, and vise versa. Any better way to test each board?