I recently acquired a 17in G5 Imac that was missing a power supply and a hard drive... hard drive was no problem... got a terabyte hard drive (bigger, better, faster right)?

I am moving on to the power supply... I looked for weeks and the cheapest power supply was approx. $100... I am not paying that much for a freakin' 250 watt power supply!!!

Anywho... I do not want to fry a perfectly good Imac so I used my googlefu and found the following links... the problem with them all is that some of them mention that an ATX power supply does not have the 24v power rail needed for the screen... and that I need a power supply with a +12v and a -12v to make a 24v rail to power it... I can't find anything confirming/denying this.

http://www.jimwarholic.com/2008/11/apple-imac-g5-power-supply-issues-and.php

http://pinouts.ru/Power/atxpower_pinout.shtml

http://forum.insanelymac.com/index.php?showtopic=47788

http://forums.macnn.com/58/imac-emac-and-mac-mini/353353/imac-g5-power-issues/

I am planning on taking an dead power supply and cutting off the connectors and making an extension that way i can reuse the power supply if needed... the good power supply that I am going to use is a 500watt antec power supply (model BP500U). It has a +12V rail rated at 18A and a -12V rail rated at 0.5A.

To get the required 24V to run the internal monitor I am planning on cutting off the insulation on one of the 12V rails and soldering on the other 12V rail and then re-wrap with electrical tape.

What I was wondering is that can anyone find a more definitive guide to doing this... preferably with the instructions on how to get the internal screen up and running with (if it is really) 24V?

Anyone see any flaws in my plan (or suggestions/comments)? Like I said I do not want to fry my new toy and any help would be appreciated.

Thanks in advance ya'll.

Update... found a webpage that claims that it works perfectly fine without the 24V pin connected... he suspects it is used for powering firewire.

http://hk.myblog.yahoo.com/hoodmulti/article?mid=54

Any Ideas?

The G5 uses 24 vdc for the firewire. The IEEE 1394 spec allows 8 - 30 vdc. Apple's implementation on laptops is typically related to battery power and can be as low as 9 vdc and usually about 12 vdc. To get power to your firewire port connect the 24 vdc input to 12 vdc on the atx supply.
The 12 vdc is within IEEE 1394 specs and similar to what is found on the Apple laptop.

So it should work perfectly fine with the pins rearranged and only a +12V going to the 24V pin correct? I do not have any firewire devices but it would be nice to leave the option open...

Once again thanks cerb...

Seems how I have found no definitive/authoritative guide to doing this I am going to document this with pics so that there is one... I will add this to our growing repository of guides.

Ok... found these links that claim that the lcd will not work without 20v connected.
(sorry this is taking me so long guys... I work on this when I can)

http://www.xlr8yourmac.com/archives/feb09/021209.html

http://gallery.me.com/iamkimc#100033&view=mosaic&sel=0

Cerb... do you by chance have a data/spec sheet for the G5... something that is really detailed... or the pinouts for the OEM apple power supply?

Some people say it works without +24, some say it is required. It might vary with internal revisions. Give it a try without +24 and see what happens.

A couple of links:
http://www.insanelymac.com/forum/index. ... pic=105113
http://www.insanelymac.com/forum/index. ... opic=47788
http://www.jimwarholic.com/docs/Apple-i ... Supply.pdf

Some options if +24 vdc is needed:
http://www.allelectronics.com/make-a-st ... PLY/1.html
http://www.autoelect.com/wp/Specs/produ ... ndex.shtml

I can confirm that a quick snip of the 2 yellow 12V cables form the small square block on the ATX PSU and cut the cables at pins 12 & 18 on the main block. Connect the yellow cables to pin 12 & 18 and off you go. This has worked for me on a 17" Imac G5 and the screen DOES work.

Cal.