Quick iMac G3 conversion question

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mac-man6's picture
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I'm attempting the trayload ATX converstion using the guides on radio mods and http://members.fortunecity.com/tinux1/sites/imac-atx.html. I like the simplicity of the fortune city one, even though it doesn't have softpower. The problem is that I don't have the power filter board any more, so there's just the 26 pin connector on the motherboard left to connect to. You can see an image of the connector here. http://www.radiomods.co.nz/imactoatxconversion/logicboardpowerconnector.jpg All the sites for Rev. A-D G3 iMac hacks involve the 24 pin power filter board.

Radio Mods has this pin out diagram but I need more information. The powerboard filter had a 5VR, 5VS and 3.3VS that aren't used in fortune city hack. But I don't know which pins this would relate to on the 26 pin connector. The apple service manual for Rev A-D doesn't have this pinout.

T+5V GND GND +3.3 +3.3 -12 GND GND +12 +5 +5 GND +12 -function
26 24 22 20 18 16 14 12 10 8 6 4 2 -pins
25 23 21 19 17 15 13 11 9 7 5 3 1 -pins
PFW GND GND +3.3 +3.3 +3.3 GND GND GND +5 +5 GND +5 -function

Do you know where I can find a more detailed pin out? Or can you help me identify which pins are 5VR, 5VS and 3.3VS. Thanks!

p.s. The plan is to is to solder like wires together and have a pushbutton switch to ground to turn on the ATX power supply.

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Eudimorphodon's picture
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Joined: Dec 21 2003
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Here:

All the pinout you need is the radiomods site you mention.

http://www.radiomods.co.nz/imactoatxconversion/

"5VR, 5VS and 3.3VS" are, from what I can tell, just arbitrary names Apple labeled the connector with. (It's possible the Apple power supply in the original unit does something special with them, but the motherboard doesn't care.) I've made a direct-to-the-motherboard converter cable based on the pinout at radiomods and it works fine. Just applying +3.3v, +/-12v, and +5v to the appropriate points marked in orange, blue, yellow, and red on the chart will bring the board up.

The inverter circuit on that site is dead simple to construct, btw. It's picky about what supplies it'll actually shut off, but it's probably worth at least trying it on yours. (Without soft power working "shutting down" the OS will actually trigger a reboot. Yes, you can then turn off the power manually, but with OS X at least it'd always get far enough to leave the disk in such a state that the OS would insist on fsck-ing it next time you powered on.)

--Peace

mac-man6's picture
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Joined: Jan 11 2006
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"Just applying +3.3v, +/-12v,

"Just applying +3.3v, +/-12v, and +5v to the appropriate points marked in orange, blue, yellow, and red on the chart will bring the board up."

And black, I suppose.

Eudimorphodon's picture
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Joined: Dec 21 2003
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Well, yeah. Having grounds so

Well, yeah. Having grounds sort of goes without saying.

Keep in mind of course all advice comes with no warranty, expressed or implied. ;^)

--Peace

mac-man6's picture
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Joined: Jan 11 2006
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It works!

I was about to ask some pin troubleshooting but then I saw I left out connecting T+5V on the iMac to +5VSB on the ATX. Once that connection was made it was up and running. Now I just have to find out why I don't get any sound.

But thanks!

Eudimorphodon's picture
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Yay! Good luck. For sound I u

Yay! Good luck. For sound I used the original little board fragment and cabling that carries the headphone jacks, so I can't comment on getting it straight from the motherboard.

Of course I eventually ended up giving the whole pile of bits away to someone more motivated, after I came to the conclusion that a Rev. B iMac in any other case is still a Rev. B iMac.

--Peace