This page is updated continuosly
Disclaimer
I don't take any responsibility for anything you might do with the information the information on this page. It's you're own fault if you damage your iMac. With that said, I move on to the more important stuff:
Sections
Introduction
Power: ATX power converter
Power: Using the iMacs power supply
Video: Pinout listing
Video: iMac to DB15 converter
Video/Power: Creating PFW for the DB15 converter
Video: iMac to VGA converter
Sound: using the 26 pin header
Status
iMac taken apart
Planning and writing schematics
I don't own a digital camera (and can't afford one), so I will not be able to show any pictures until someone borrows me a camera.
Crew
William Westman Malmi [william.westman@umea.se]
Members of 99mac.com (a Swedish Mac-forum) [http://www.99mac.com]
Special thanks to: Samuel K
The discussion that started this project [http://www.99mac.com/forum/showthread.php?s=&threadid;=14239&perpage;=15]
Important discussions
Applefritter "irack dv" [http://www.applefritter.com/cgi-bin/YaBB/YaBB.pl?board=hacks;action=display;num=1042516415]
Getting to it
There's a couple of people who have converted an iMac rev A-D (233 - 333 MHz) to be fitted in a PC-case. For example the iBox [http://www.applefritter.com/hacks/ibox/index.html] which is a somewhat crude but effective modification of the iMac. That conversion uses the iMacs own powersupply and the internal display connector which the iMac rev A-D has. This connector is just a DB15 (D-sub15, a regular Mac video connector). This makes the rev A-D iMacs perfect for putting in a PC-case. You don't need to do anything with the electronics, just take it out of the iMac-case and bolt it in the PC-case. Very plain and simple.
If you don't want to make you're own custom made box, just buy one from Marathon Computer [http://www.marathoncomputer.com/irac.html], but I warn you - it costs $399. This kind of conversion costs under $150 depending on if you have the correct tools for the job or not. If you have the tools and don't need to buy a PC-ATX-case, it will probably only cost you about $10-20 for the electronics.
With the iMac Slot-loading (350 Mhz - 600 MHz), it's a whole different deal. The powersupply is built in a very unpractical way, it's on both sides of the motherboard (divided by a divider panel) and the Video connector is a special purpose-built connector for the iMac. What we have to do to get a Slot-loading iMac into a PC-case is to create a way of connecting a more practical power supply (like the ATX) and convert the signal from the iMac display connector to DB15 or HD15 (VGA).
Tomoyuki Katayanagi have done this with his conversion of an iMac DV [http://www.webdrive.jp/mac/]. He has been so kind to translate his 3rd (and most important page) to English [http://www.webdrive.jp/mac/iMIU03e.htm]. I'm trying to replicate his success with my conversion of an iMac Slot-loading (350 MHz).
Tomoyuki used a pretty simple solution, he converted power from an ATX-power supply through his homemade circuitboard. Something I'll try replicating. He got video by converting the 20 pin video connector to DB15. I'll try to use HD15 (VGA) instead.
ATX power supplyThe first problem is to convert power from the ATX power supply so that the motherboard can use it. It's possible to make a solution for this if we know how much power we get in each cable and where to put it. We know how much power an ATX-power supply gives us, this can easily be checked [http://www.intel.com/design/motherbd/atx.htm].
| ATX | |||
| Function | Pin | Function | |
|
+3.3 VDC or 3.3 V sense |
11 | 1 | +3.3 VDC |
| -12 VDC | 12 | 2 | +3.3 VDC |
| COM | 13 | 3 | COM |
| PS ON | 14 | 4 | +5 VDC |
| COM | 15 | 5 | COM |
| COM | 16 | 6 | +5 VDC |
| COM | 17 | 7 | COM |
| -5 VDC | 18 | 8 | PW OK |
| +5 VDC | 19 | 9 | +5 VSB |
| +5 VDC | 20 | 10 | +12 VDC |
And the suggested wire colors for the ATX power supply. This is just a RECOMMENDATION, not a fact. So the ATX cables you buy in the store MAY have a different coloring.
The real problem is how is the iMac power connector constructed?
Mr Katayanagi has collected this:
We know this from the Manual:
| iMac power supply | |||
| Function | Pin | Function | |
| ? | 11 | 1 | ? |
| ? | 12 | 2 | +5 VDC |
| ? | 13 | 3 | ? |
| +3.3 VDC | 14 | 4 | +12 VDC |
| ? | 15 | 5 | ? |
| ? | 16 | 6 | ? |
| ? | 17 | 7 | ? |
| ? | 18 | 8 | ? |
| ? | 19 | 9 | ? |
| ? | 20 | 10 | ? |
Mr Katayanagi's power converter looks like this:
What is needed to create this ATX converter board?
These components are needed (alternate version of mr Katayanagi's list):
| Component | Quantity |
|
HD74HC04P Regular IC |
1 |
|
Diode 1S1588 Switchdiode Interchangeable |
2 |
|
Transistor 2SC1815 Interchangeable |
2 |
| Condenser 0.01 mu F | 1 |
| Condenser 0.47 mu F | 1 |
| Resistance 100 Ohm | 6 |
| Universal baseplate | 1 |
| ATX cable extension | 1 |
| Pin header | 10 |
| Original power connector from iMac | 1 |
Cost: about $10
Information regarding components mentioned:
Diode 1S1588 [http://dns.madlabo.com/mad/edat/spice/ex2/]
Transistor 2SC1815 [http://www.semicon.toshiba.co.jp/en/bucat_8/bucat_3/bucat_2/td_39/TD.pdf]
Since it could be difficult finding the suggested diode and transistor outside of Japan, you could probably try and replace the diode and transistor with something else. That's what we're trying to do. We're using a fast switching diode 1N4148 instead of the 1S1588, and we'll probably use transistor BC337-25 isntead of the 2SC1815.
Information regarding substitute components:
Diode 1N4148 [http://www.marvac.com/surplus/1n4148.htm]
Transistor BC337-25 [http://www.google.com/search?num=50&hl;=en&lr;=&ie;=ISO-8859-1&q;=BC337-25]
Pinout listing
Good pinout-listing for video conversion [http://www.acl.co.uk/pinouts.htm]
Using the iMac's original power supply
Roger Leenes suggested that one could use the original power supply instead of converting ATX, like a couple of people has been doing with the conversion of the older iMacs (rev A-D). The problem with this is size, the original power supply is placed on the backside of the logic board and needs a lot of space.
Mr Leenes has got some problems with the voltage on some of the connectors. This is what he writes:
It is not 24V AC that comes out of the analog board. I only get a reading if I put the multimeter on AC voltage, but as I mentioned before it is not straight AC (sine wave). In one setting I read 24V, whereas I get another reading if I switch test leads. On my simple oscilloscope I get spikes, supporting the multimeter readings. This leaves me in the dark for now. Someone with a decent oscilloscope should test the power lines.
He's testing an European iMac running at 220-230V. He will continue testing the iMac's power supply and we will put the results here on this page. Could more people try to figure out how much electric current that flows through the different connectors?
iMac display connector to DB15
One way to convert the video-signal from the iMac display connector is to convert it to a DB15 connector. This is pretty straight-forward since mr Katayanagi has been kind enough to supply a pinout for the iMac display connector:
| iMac display connector (iMDC) | |||
| Function | Pin | Function | |
| SDA | 1 | 2 | SCL |
| GND | 3 | 4 | ? |
| DC0 | 5 | 6 | 5VSB |
| ? | 7 | 8 | -10V |
| Hsync | 9 | 10 | PFW |
| Vsync | 11 | 12 | ? |
| Blue | 13 | 14 | Blue return (ground) |
| Green | 15 | 16 | Green return (ground) |
| Red | 17 | 18 | Red return (ground) |
| ? | 19 | 20 | ? |
The pins marked with dark grey is not used in the iMDC -> DB15 conversion. The ones marked with green has to be connected to the ATX power converter.
The pinout for the DB15 connector [http://www.diyha.co.uk/electronics/mac_video.html]:
| DB15 | |||
| Function | Pin | Function | |
| Red ground | 1 | 9 | Blue |
| Red | 2 | 10 | - |
| Composite sync (H) | 3 | 11 | GND |
| Sense 0 | 4 | 12 | Vertical sync |
| Green | 5 | 13 | Blue ground |
| Green ground | 6 | 14 | GND |
| Sense 1 | 7 | 15 | Horizontal sync |
| Reserved | 8 | ||
Two simple schematics for the iMDC to DB15 converter:
Components required to create the iMDC to DB15 converter:
| Component | Quantity |
| 20 pin connector | 1 |
| Small cables for connecting the 20 pin connector to the 15 pin connector | A couple |
| DB15 connector with the possibility to solder on your own cables | 1 |
| ATX converter board | 1 |
How to create PFW for the DB15 converter
What is PFW? XRayNuke gives a good answer at Applefritters forum (link at top of page):
"PFW means "Mac power-control signal" everywhere I've seen it. I think it stands for Power Fail Warning, which makes sense because it's used for shutdown as well as startup. You'll notice that the PFW line on the diagram is a slightly different color from the FireWire supply line, and a "PFW conversion circuit" is mentioned: one of those pops up in every Mac-ATX hack for power control. Indeed, the author links to XLR8YourMac on the second page."
Use this schematic to create a conversion on the ATX converter board:
iMDC to VGA convertion
Instead of converting to DB15 which is a standard that is almost obsolete, we could convert the video-signal to HD15 (VGA) instead. This would make it easier to connect to a modern external monitor without the hassle of using a DB15 to HD15 external converter (which cost about $15).
This is the pinout of a regular DB15 to HD15 converter. Since we know how to convert iMDC to DB15, we could use this as a model for our iMDC to HD15 converter.
Sound and other connections
The motherboard has a 26 pin connector which is used to connect to speakers and other internal functions.
Thanks to Ravik at Applefritter forum (link at top of page) we know the pinout of the 26-pin header. The pinout is the following:
| 26 pin header | |||
| Function | Pin | Function | |
| Microphone (white) | 1 | 2 | Microphone (black) |
| Microphone (red) | 3 | 4 | Headphone Board (yellow) |
| Headphone Board (blue) | 5 | 6 | Headphone Board (brown) |
| Headphone Board (red) | 7 | 8 | Headphone Board (purple) |
| Headphone Board(orange) | 9 | 10 | Headphone Board (green) |
| Headphone Board (black) | 11 | 12 | No Connect |
| + Right Speaker (red) | 13 | 14 | + Left Speaker (red) |
| - Right Speaker (black) | 15 | 16 | - Left Speaker (black) |
| Power Switch/LED (white) | 17 | 18 | Power Switch/LED (white) |
| Power Switch/LED (green) | 19 | 20 | Power Switch/LED (red) |
| No Connect | 21 | 22 | No Connect |
| AC+ (red) | 23 | 24 | AC- (green) |
| AC+ (white) | 25 | 26 | AC- (black) |
Firewire 15V
The iMac DV and later models (400-600 MHz) has Firewire built in. Firewire uses 15 V to power the external units connected to it. An ATX-power supply does support this if it has the optional connector which has 15 V for Firewire. If your ATX-power supply don't have this, you have to convert power so that it has 15 V out. The easisest thing though, would be to get an ATX-power supply which fo support 15 V.
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