If you still have your first 2.3, have you swapped the board and confirmed that the problem follows the board? Does the non-working 2.3 come alive and the working one die?
Have you checked the supply voltages with the board in and out? If there is a fault on the board that's pulling the supply down, you should find out this way.
Also, try pulling all of the socketed parts from the board and see if it boots this way. If the dead 2.3 works with the board from the other one, then you could try swapping ic's one by one between the boards to determine whether or not a problem follows an ic.
I'm assuming that you've checked the battery on the i/o board, and that it's OK, and there has been no damage to traces or components from a leaky old battery. That's a common problem with old 2.3's (and all 80's, 90's gear!).
Don't give up!