SL iMac G3 -> ATX mod

Are you using a 350 or one of the faster ones? If it's anything other than an first revision 350 it'll already have a VGA port on it. The 350 has the holes for one, but I dunno if you can just solder one in and have it work.

http://www.wap.org/journal/irack/default.html has the iRack DV with a 350 mobo in it. It appears that the video connector is just adapted straight from the video connector to a VGA connector with a ribbon cable. From those photos I can't see how the power is adapted. There are surely other sites with iRack info or similar mods.

All of the CRTs in my iMacs have died...2-233s and a 266 Strawberry. When you remove the lower case plastic of the iMac, as if to remove the component sled, you have to disconnect the internal CRT cable. This is just your everyday, average-joe little Apple video port. I have an Apple-to-VGA adapter, and all I did was pull off the internal plug, stick the adapter in it's place and hitch my VGA monitor to it. Why solder and crap when you can just buy one of these almost-too-cheap small little adapters and go?

It's funny, there's something engraved into the metal next to the port that says something about not hooking an external monitor up. I've had no problems, they just want you to pay them to repair the interal CRT. Psh, wolves.

-Collin

Yep, that works on trayloaders, however slotloaders are an entirely different machine inside. All but the first 350 model have a VGA plug on the mobo, just for an external monitor.

in my expierience with imac DV400 the monitor port doesnt work without the built-in crt hooked up....

I've brought back a 400 mHz Indigo iMac using several online pages. In fact I'm using it to post this message. It's sitting in front of me waiting for a new case. I plan to make new video connectors using internal SCSI connectors cut to fit. I tried to use the rear video port but I get a dark, blurry screen. This is my first mod.

I couldn't figure where to place the +5v line for the soft power up but then I remembered that I grounded the green wire on the ATX power supply to test it. So I put a rocker switch between them, then pushed the iMac's front power switch to start up. When I attach this set-up to the 500 mHz Indigo iMac it starts up as soon as I flip the rocker switch.

So far I've scrounged from my junk pile for the power supply and only paid $16 for a new 20 cable, transistor/resistors and copper clad boards.

These are the pages I used for my final conversion (I have a dozen others but they involve the Rev A-D iMacs):

This guy has photos and pinouts of the iMac connectors on page 3:
Also a link to a manufacturer that sells the connector for the power board if you don't want to desolder/rip-apart the existing one.
http://www.hardmac.com/articles/39/page1

Slot-loading iMac with Soft-Power start up
http://www.radiomods.co.nz/imactoatxconversion/

A good conversion project with the adaptor I used for the video. This didn't work with the 500mHz iMac but I'm still testing it.*
http://www.cryogenius.com/hardware/imac/
He has an interesting way to make a circuit boards without chemicals.
http://www.cryogenius.com/hardware/pcb/

*the author mentions a problem with the video and I am experiencing some ghosting, black letters/lines look purple. I'll try to find a shorter video cable to the monitor but if anyone has another idea on how to overcome this please let me know.

David

That's a good list of sites. I really like the Dremel'd circuit boards. I'm going to have to remember that for some hacks in planning. I also like the Rainbow conversion, but the French guy gets a lot of points for doing nice work with the soft power!

A lot of these mods rig soft power so that the power works just like it did originally. Thus you can shutdown from inside the OS, start from the keyboard, etc. To hard power you would likely jus thook up the correct power lines as shouwn above and just switch the power as you described. But, if you use an ATX you are going to have to rig the softpower anyway, so why not do a bit more work and get it to the softpower convenience?

Some of these are already probably mentioned but these are the sites I've found while searching. I like the French MacBidouille site the most.

http://www.radiomods.co.nz/imactoatxconversion/
http://www.cryogenius.com/hardware/imac/
http://www.xlr8yourmac.com/systems/imac_in_PowerCenter_case/iMac_in_powercenter_case.html
http://www.xlr8yourmac.com/systems/IIci_imac/imac_in_IICI_case.html
http://www.mlode.com/~stuka/imac-atx/
http://members.fortunecity.com/tinux1/sites/imac-atx.html
http://www.command-tab.com/index.php/imac-lc-iii/
http://www.hardmac.com/article.php?id=39&page=2
http://www.webdrive.jp/mac/iMIU03e.htm

...just purchased a 400MHz DV logic board off ebay to do my own conversion.

There's a difference in method for connecting the ATX PSU for the DV iMac...

1) The ct-scan.com method connects ATX pin #9 (+5 VSB standby) to a jumper near the PRAM battery, and pin #14 (PS on) to any ATX ground.

2) The other methods I've seen require an inverter to change the low-level power ATX power on to the high-level power on of the iMac.

Is method 1 a later-discovered solution to avoid using the inverter, or is the ct-scan write-up missing information?

edit: Looking at the cryogenius link, which also used the J9 jumper for +5 VSB, he's accomplished soft-booting by using a transistor to switch the ATX power to ground. This looks like the route I'll take, as I'll likely have all the parts on hand. ...providing the as-is iMac board I've bought actually works

My attempt.. I just wired up my 400 DV and as I was soldering the wires in for the power supply I knocked off the cap on the back of the board between pins 6 and 8 ( +5v and the ground ) anyone know what I should replace it with..

I have my speaker harness attached but no video cable.. and when I apply power I get no tones, but i get the main yellow power light on, and it looks like its flickering between green and yellow..

Any Ideas???

I've succeeded in getting my iMac DV 400 board to power up.

It's displaying video through the VGA port, though as others have found above, it looks like stink, so I'll have to make an adapter off the 20-pin video connector instead.

I used the transistor method (cryogenius link above) with a 2N222 and a 3K-ohm resistor (scrounging what I had on hand).
dmac4 and macman6, your links were invaluable.

Still got a long way to go: video, sound, and of course, a case...

Cool! So, what did you do for a heat sink on the CPU? I know there is one stock on the GPU, but did you adapte a Pentium one or something?

...that old thing.

Heat sink's on my to-do list as well. For testing I had an old P1 heatsink balanced on the CPU.

A Pentium heatsink won't sit centred on the CPU, thanks to some tall greeblies on either side of it, so it's going to be a challenge. I considered using epoxy, as some PCers have done with their GPUs, but so far all my mods have been non-permanent, and I'd like to keep it that way. Stay tuned...

One of the above mentioned sites reminds us, "Do not forget to put some thermal grease on the CPU before sitting the heatsink on it."

Here's a little-known tidbit; you can substitute Desitin for thermal grease! So if you're in the midst of a hack job, you realize late at night that you forgot to pick up some thermal grease, and you've got a fairly new crumb-cruncher at home, you may have just what you need in the diaper bag! (And it might save a few bucks as well if you were to buy the baby crack spackle instead of the thermal grease.)

Apparently the main component in both Desitin and white thermal compound is zinc oxide. Not sure if you can use thermal compound on the baby's rump though. I'd do a little further checking on that first.

I considered using epoxy, as some PCers have done with their GPUs, but so far all my mods have been non-permanent, and I'd like to keep it that way. Stay tuned...

Don't use epoxy. Instead, use thermal adhesive; the makers of Arctic Silver thermal paste make a version with a strong adhesive built into it. If you don't want something permanent, then you'll need to go with a mechanical solution to hold the heatsink down (e.g. a clip).

From about 1 week I'm modifying a broken iMac 500MHz, and found this same problem... the solution is not the cable, 'cause it isn't a long cable problem. You have to plug a -10 voltage to pin 8 of the video connector, voltage that is provided from the video logic board of the CRT. You can create it from the -12 ATX connector by placing a uA79L10 or with 2/3 diodes in serie.
Another thing I've done is to use the pins 1 and 3 of the connector near the PRAM battery instead of using an inverter to switch on the ATX power supply.

Bye bye
l0v3r

I've got a problem now... in the monitor settings (using OSX) I can select only from 640x480 to 1024x768 with fixed frequency like if there's the old CRT. How can I do to change resolution to 1280x1024 and select the frequency I want?

Thank you

bye bye
l0v3r

Have you got your iMac DV conversion going yet ? I'd be interested to know how it went.
I'm doing the same conversion (using the excelleny Hardmac article: http://www.hardmac.com/articles/39/page3)

If you're stripping down an iMac with a failed monitor, it makes sense to keep as much attached to the motherboard as possible - so I've remounted it on the aluminium baseplate (minus the down converter board) and kept the 26 pin HE10 connector for headphones, speakers, microphone etc attached, so will hopefully be easy to reconnect them. I just need to pluck up courage and get the soldering iron out!

My DV board's been sold to Davintosh, so he's the one we're all waiting on

I shouldn't post "in-progress" projects, because I seem to get distracted too easily by the next shiny object that comes along.

My DV board's been sold to Davintosh, so he's the one we're all waiting on

I shouldn't post "in-progress" projects, because I seem to get distracted too easily by the next shiny object that comes along.

Huh, wha... Is somebody lookin fer me?

Sorry, musta been sleeping & missed the activity on this thread. Are we looking for how something is wired on the board I got from eeun?

It was asked if I'd finished my iMac -> ATX project, so I just passed on that the project was passed on.;D

This felt like one of those questions that get asked when you're daydreaming in class.

Actually, it was what, mid-March when I got the iMac board, and I have yet to so much as plug it in. I do have plans for it (see the iDesk thread) but have been up to my eyeballs lately with a kitchen remodel, a kid graduating from high school, two kids heading off to a foreign country on a missions trip, 50 hour workweeks, helping my employer plan construction of and a move to a new facility, and trying to breathe amidst all that.

I've gotten as far as purchasing the parts & materials for the iDesk, but haven't put anything together for testing. I'm thinking mid-July... Maybe.

Have you got your iMac DV conversion going yet ? I'd be interested to know how it went.

I converted one a few weeks ago... didn't have any real problems besides finding a monitor that would actually sync to the frequencies

I also had to solder a jumper in next to the battery and put 5v trickle on to one of the pins (don't remember which). I accomplished softpower with a small transistor NOT gate.. any small NPN transistor and two 10k resistors should do it.

I did post up a forum post about it entitled "iDrawer" but Tom pulled it and asked me to make it a story... which I will do when I get home from Australia.

So uh... any questions?

l0v3r
With a new cable made from an internal floppy cable I have clear video for my 400mhz iMac but the 500mhz iMac has a dark blurry screen.
How could I use the -10v in my setup? on this page... http://www.applefritter.com/node/10574
Does it go on one of the lines to the monitor?
Thanks,
David

From about 1 week I'm modifying a broken iMac 500MHz, and found this same problem... the solution is not the cable, 'cause it isn't a long cable problem. You have to plug a -10 voltage to pin 8 of the video connector, voltage that is provided from the video logic board of the CRT. You can create it from the -12 ATX connector by placing a uA79L10 or with 2/3 diodes in serie.
Another thing I've done is to use the pins 1 and 3 of the connector near the PRAM battery instead of using an inverter to switch on the ATX power supply.

Bye bye
l0v3r

Sorry for bringing up an old topic. Is there anyone who can do the power adaptor and video adaptor for me? I'm willing to trade my Power Mac 7100 (yellowed, no drives) and Performa 600 (good condition, 160MB HDD, caddy loading CD drive with no caddy, and 1.44MB floppy) for payment. I don't know how to do this, plus my dad won't let me anyways because he thinks I'll cause a fire when I plug it in.