Well I managed to replace three chips and it works fine all the time now with my centris 650 PSU, shutdown is odd though, says "its now safe to switch off your macintosh" and proceeds to shut down seconds after displaying the message. Going to wire my ATX PSU for the IIci now.
Photo is old, trace has been repaired and capacitors were installed.
Hi Jon183, it's been a while since you posted this so this is a long shot but I thought I'd give it a try.
I have a similar issue to you. I dug up my 30 year old Mac IIci and it didn't boot properly (It started up a couple of times, no sound, and then eventually it stopped booting completely). I cleaned the board with alcohol and replaced all caps. I actually recapped the PSU as well (all caps apart from one cap, which was impossible to reach) Now it starts up fine. I have sound too. But when I go to shut down, it gives me "It's now safe to switch off your machine" and stays there. In your case, you stated that it shuts down after a few seconds. In my case, it stays with the message. The only way to shut it down is to pull the main plug, which is a real hassle.
I actually worked on this last Aug and I left it at this. I started looking at it again and I found your post.
Did you ever manage to find out what was causing this message to come up in your IIci?
Here is my post from last year for reference.
Thanks.