okay so here's the plan of attack for #marchintosh - there appears to be no 28v on the existing power supply...but I have a bare supply that can be coerced to 28v.
however, it does not fit in the original sidecar due to being too tall.
still unsolder the ac/dc plugs from the OEM PSU and see if the cube powers up, than look closer at what PSUs might fit in this box.