This is really the way to go with dead/dying IIci PSUs. I don't think it is worth recapping old power supplies like this anymore. There is nothing special about the original IIci power supply. The original Astec/Delta units are way beyond the end of their designed lifetime now. The other benefit of an ATX-based PSU is that it will run cooler and more efficiently than the original PSU, and has all the modern safety features that 80 plus rated PSUs have.
The IIci PSU pinout was also used for the following models: Quadra 700, Macintosh IIcx, Macintosh IIvx, Macintosh IIvi, Power Macintosh 7100, Quadra/Centris 650, aaand I think the Quadra 800 but the 800 has a different formfactor case for the PSU housing.
Here's my attempt at a 'stealth' IIci PSU, which uses a 250W Seasonic SFX unit inside the original housing. I even moved the Seasonic sticker across to replace the Astec one, so it looks like it's always been this way.
The Seasonic PSU has a built-in thermometer sensor so the fan speed is controlled from that.
Since replacing my PSU, I've had no issues with soft power - it acts really fast when the ADB keyboard power key is pressed, just as it should.
The soft power circuit I used:
View attachment 6436
My original PSU:
View attachment 6437
The Seasonic had its own filtering on the back of the AC socket, so I moved this across to the Astec housing.
View attachment 6438
The original Astec sockets were removed:
View attachment 6439
I installed new stand-offs into the bottom of the Astec housing. Went through two drill bits doing that, oops. But this meant I could dispose of the Seasonic PSU housing and just keep the Seasonic PCB and move that into the Astec housing.
Here it is all wired up to the original motherboard connector:
View attachment 6441
And all done, you can't tell anything was ever changed.
View attachment 6440
