IIci will not power on - appears to be a PSU issue

[shifuimam]

I came back from a short vacation to a non-booting IIci. The keyboard power button results in nothing but a click of the power supply, a short power-on of the monitor, and a quick flash of the keyboard and case LEDs. I pulled the PSU and shorted pins 8 and 9 to test the supply by itself, and it's definitely a problem with the power supply. With those pins shorted, it clicks repeatedly until I unplug it, like it's power cycling nonstop.

I've done some research, and I'm wondering if it has to do with this +5v trickle issue with Astec branded power supplies (like mine). Should I do the repair referenced in that article, or is the problem something else?

Prior to my vacation, this did happen occasionally - I'd have to flip the power switch on my surge protector a few times before the machine would actually power on. Additionally, the power switch on the back of the case has never worked (same click except without the monitor powering on briefly).

 

[olePigeon]

Wouldn't hurt to recap the power supply.

 

[uniserver]

If you want take some decent pictures of the inside of your PSU, maybe we can visually figure out what cap(s) are bad.

 

[shifuimam]

I was able to get part of the enclosure for the PSU apart, but there are two circuit boards - one on top, one on bottom - that appear to be attached to each other at several locations with soldered wire. Is there any guide on the best way to disassemble one of these things?

 

[shifuimam]

Pics are on my Flickr account...too many to link here, plus you'll probably want to see them full size. They're not great, but it's impossible to separate the two boards without desoldering a bunch of stuff.

 

[shifuimam]

So we found out a few things - the +5v trickle is dropping, even with that little diode hack. Adding an external 5v power supply to that pin (via a cannibalized BlackBerry charger) works if the PSU isn't installed in the IIci. As soon as it's installed, the same problem comes back.

It's looking like it might be the voltage regulator, or something else. Rather than try to dismantle the IIci PSU (it's a real beast), we are going to replace it with a very similar PSU pulled from an old HP desktop. The form factor is almost identical, so it should be fairly trivial to install the HP PSU's circuit board inside the steel enclosure of the IIci's failing PSU. We'll see!