Imac G3/600 to ATX with green screen

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Joined: Mar 6 2006
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I'm doing my first Mac project - fitting a G3/600mhz logic board from an iMac with PAV issues into an ATX case using this site http://www.cryogenius.com/hardware/imac/ and others as a guide. It all works a treat (including the soft boot setup) except that the screen is green and fuzzy as per the photo. I've tried the setup with a 400DV logic board and the display is perfect. I've tested the 600 board in another iMac and its also working fine.

I'm wondering if there was a slight change in the video wiring in the later model iMacs. I've searched but can't find any video pinout info on the later model boards - only Rev E 350/400DV's. Does anyone have any clues about this?

Cheers

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Joined: Sep 3 2004
Posts: 170
what happens when you plug in

what happens when you plug into the video out (mirror port)??

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Joined: Mar 6 2006
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It's the same green screen, I

It's the same green screen, I'm afraid.

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Jon
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Joined: Dec 20 2003
Posts: 2804
It shouldn't matter as you ar

It shouldn't matter as you aren't using the original PAV, but does that have the firmware update installed? That's usully the first thing we ask about concerning iMac video problems.

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Joined: Sep 3 2004
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yea, make sure your firmware

yea, make sure your firmware is updated

if it is updated, then you may have a logic bord problem

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Joined: Mar 6 2006
Posts: 4
The board has the firmware up

The board has the firmware update and I've tried it in another iMac 600 and it works perfectly. That's what led me to wonder about the wiring.

There's also a thread on Applefritter from last year about a G3/500 with the same issue but unfortunately there was no resolution to the problem on the thread. Given that the boards on the 500/600/700 are noticably different to the 350/400's (eg the processor is in different spot) makes me wonder if there's also differences in the video circuitry.

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Joined: Dec 19 2003
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This sounds familar

I have exactly the same problem doing the same hack on an iMac 600Mhz. Did anyone figure out why this is happening?

Eric

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Eric

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Joined: Mar 6 2006
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No luck with this

I tried fiddling a bit more with the video wiring on the 600mhz board but didn't have any success so I ended up using the 400mhz board after all for the ATX box. It's ended up being a very reliable machine - we've used it for nearly 3 years now as a music server with no problems.

Best of luck finding a solution to the 600 issue.

Graz

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Joined: Dec 19 2003
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darn...

Well that's annoying... It works very well other than that. It's got to be something simple you'd think. Maybe I will just have to settle for something a little slower. I'm looking to do something similar to you with the addition of DVD playing abilities to replace our failing DVD player with something a little more elegant.

Thanks for the response...

Eric

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Eric

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Joined: Dec 19 2003
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Here's the solution!

After a lot of research it looks like all that was necessary was to have -10v applied across pin 8 of the video connector off the motherboard.

All that's needed is a -10v voltage regulator to throttle down the -12v wire from the ATX PSU to give the motherboard what it needs.

I used a LM337 variable voltage regulator with R1 = 470 ohms and R2 = 3.3 kohms.

I now have a very happy 600MHz G3 iMac with an ATX PSU!

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Eric