Power supply debugging advice (Interact Model One)

While I wait for PROMs to arrive for my 11/05 I've pulled another "back-burner" project off the shelf. It's an Interact Model One (http://oldcomputers.net/interact.html) and it's having power supply issues. The symptom: At initial startup after being off for any significant period of time (say, 10 minutes or longer) the +5V comes up for 2-3 seconds then drops to zero. The other supplies (+/- 12V) are fine. What I've done so far: - Recapped the electrolytics in the supply (I had the parts on hand, and it's three capacitors. Sorry for the shotgun approach, Tony :)). - Removed socketed 2114 RAMs (in case one was shorted). No change in behavior. The power supply and logic are incorporated into a single PCB, so it is difficult to separate the two (I guess I'd have to figure out what traces to cut, and I'd rather not mangle things if I can avoid it). The DC supply is fed by an external "wall wart" which I *believe* just contains a transformer -- it outputs several flavors of AC (16.5V and 19V), no DC. Any suggestions for where to start with this? Power supplies are voodoo to me, still. The power supply schematics can be found in here: http://www.thebattles.net/oddments/interact/InteractSchem.pdf (page 6, lower right corner). Thanks! Josh