iMac G3 mod - Video Connector

[elvisa]

Just wondering if you've made any progress with the software control. I'm currently looking for a tray loader to
follow you with this.

Unfortunately, no. Work ramped way up late 2020, and then I had just the week off between Christmas and New Year which was all family stuff, now back to work again.

I've been meaning to connect something up to the logic board and see whether or not serial style information is passing back and forth across the 4 or so spare pins. But just no time.

 

[rockyhill]

Unfortunately, no. Work ramped way up late 2020, and then I had just the week off between Christmas and New Year which was all family stuff, now back to work again.

I've been meaning to connect something up to the logic board and see whether or not serial style information is passing back and forth across the 4 or so spare pins. But just no time.

Yup, I know what you mean, same situation here.

Hopefully I'll get some free time this month to do some more stuff.
I'm planning on designing a cabinet or stand or something around the iMac that will show it off while keeping enough of an arcade cabinet feel. You know what you're doing in this area, so any ideas/tips?

 

[elvisa]

I'm planning on designing a cabinet or stand or something around the iMac that will show it off while keeping enough of an arcade cabinet feel. You know what you're doing in this area, so any ideas/tips?

Getting the design right is key I feel. Apple always had a very specific design aesthetic about them over the years, so finding something era-appropriate for the iMac will be key.

Here's an example stand I see a lot of arcade users go for, with a curved design (ignore the joystick on top):

You could have something like that. Or just go full posh and have something designed like those marble stands they have precious jewels displayed on in movies, hahaha.

I dunno. Maybe something in between? Need to get that 90s minimalist design matched with the iMac "bubble" feel without going too kitsch.

Tricky one. I'm not much of a designer, so I tend to do a lot of image searching to try and find a style I'm after before committing to the build (which is the easy part, once you've got a design).

 

[rockyhill]

Getting the design right is key I feel. Apple always had a very specific design aesthetic about them over the years, so finding something era-appropriate for the iMac will be key.

Here's an example stand I see a lot of arcade users go for, with a curved design (ignore the joystick on top):

View attachment 1708274

You could have something like that. Or just go full posh and have something designed like those marble stands they have precious jewels displayed on in movies, hahaha.

I dunno. Maybe something in between? Need to get that 90s minimalist design matched with the iMac "bubble" feel without going too kitsch.

Tricky one. I'm not much of a designer, so I tend to do a lot of image searching to try and find a style I'm after before committing to the build (which is the easy part, once you've got a design).

I really appreciate the advice there, I'll look for stuff along the lines of what you've described here because I'm not much of a designer either and in fact my only attempt at a cabinet was a total disaster(your stuff looks great by the way!)

Going posh with custom marble and jewels would be fantastic but I think might go ahead and stick with MDF, lots of wood putty, and lots of sanding. However, you never know!

Thanks!

 

[elvisa]

your stuff looks great by the way!

Cheers. I don't have my favourite build up on my site yet though, which is this one I made as a gift for a friend:

Moon Patrol scratch build - 100% complete

Moon Patrol scratch build - 100% complete

forum.arcadecontrols.com

I need to find all my original high res photos and do a write up on my site. Lots of weird angles, and a three layer stenciled paint job. Was tricky, but so much fun.

Going posh with custom marble and jewels would be fantastic but I think might go ahead and stick with MDF, lots of wood putty, and lots of sanding. However, you never know!

I like the whole "curved" look of the iMac, and I think some concave curves would offset its convex curve design nicely (like the image I linked above, but maybe on 4 sides?). A bit tricky to do (you're going to need some thin ply/MDF/masonite that you can potentially dampen and bend), but it would be a fun project I think.

 

[rockyhill]

Moon Patrol scratch build - 100% complete

Moon Patrol scratch build - 100% complete

forum.arcadecontrols.com

I need to find all my original high res photos and do a write up on my site. Lots of weird angles, and a three layer stenciled paint job. Was tricky, but so much fun.

Holy!

That is really nice and by just looking at the pics you've given a lot of pointers. Thanks!
I can't wait to see it all up on your site.

I like the whole "curved" look of the iMac, and I think some concave curves would offset its convex curve design nicely (like the image I linked above, but maybe on 4 sides?). A bit tricky to do (you're going to need some thin ply/MDF/masonite that you can potentially dampen and bend), but it would be a fun project I think.

I agree, curves are the way to go and I wonder if an old curvy kiosk could be used or at least used as a reference design.
I've been "sketching" some stuff, going between goofy and minimalist.

 

[rockyhill]

I have a video where I take a working iMac G3 DV Ruby and swap the logic board out for the adapter boards.
This can be used as a guide while following the wiki.

 

[DurbanXe]

Jumping on to the end of this thread, however please let me know if I should start a separate one.

Rocky pointed out to me earlier that my iMac 333 (G3, Rev. D) was a much simpler setup than the later slot load models, and should work with just a straight RGBHV connection and no other modifications or I2C commands needed.

I made myself a connector to convert from the DE15 VGA connection on my laptop to the DB15 connected on my iMac, fed a 1024x768@75Hz mode to the screen via the DB15 RGB cable, and with the logic board plugged in (custom ATX connector and "audio" header that includes connections to the power button), I get a picture. Wonderful!

I've then removed the logic board, and powered on the CRT portion itself by shorting pins 23 and 24 of the power connector via a ~500ohm resistor to send +5V to the power on header. This turns the power light from off to orange/red, and gets the system fan spinning.

I then feed the same 1024x768@75Hz signal to the screen, the power light turns green, and I can hear the fan spin a little harder as well as the degausse coil click on and off, as if the CRT itself is turning on. However I get no picture, just a black screen.

Is there anything else I need to do here to get a picture? Zero changes to the RGB cable (swapping the logic board back in brings the picture back)

Pictures of it working with the logic board plugged in (RGB cable to my laptop, and not the header on the logic board):

View attachment 942289

View attachment 942288
View attachment 942290

Hi,

I have the same Imac as you, and I would also like to connect a raspberry or others to the Imac screen.
As soon as I unplug the DB15 plug from the Imac, the screen starts up.
Can you give me your cable which allows you to display your laptop PC on the Imac screen?
Thank you in advance.

Cordially.

 

[oshimai]

There's an emac repo on my github that includes the EDID and some pinouts. More to come later.

... and nothing ever came. I destroyed that eMac last year.

Over a year later I got my hands on another broken one from the trash and now have an eMac converted to a CRT monitor being driven by a LattePanda Alpha with the blind mate connector supplying the power for everything. The case was so badly scratched that I spray painted it to hide the worst bits of the domestic violence it was subjected to.

I probably have the world's only lavender-colored all-in-one computer at the moment.

Some notes for anyone else attempting this from the foundations provided by @rockyhill who I think has since moved on to other things that are more fun than this sort of torture.

• If you put no load at all on the eMac PSU it will make a whining sound
• If you put too much load on the four 28V power pins while the CRT is still off, it will assert PROT and shut down all power for a short time. Once the CRT is on you can pull about 3A (LattePanda boots and runs fine) and 3A from the CPU12V power pins.
• Putting LattePanda and an amplifier board on the 28V pins via DC-DC voltage converter again asserts PROT but the LattePanda only on 28V via DC-DC converter and the amplifier on CPU12V works great.
• VSYNC detect like on the iMac is out of the question because the CRT must not turn off while the LattePanda's PC side is awake. You need an elaborate startup sequence when the power button is pushed: CRT ON + IVAD init, LattePanda ON, amplifier ON. Similarly for sleep/wake and power off. Luckily the LattePanda exposes its ACPI power states (S0, S3, S4, S5) as pins that the Arduino can read.
• The CRT has F1 and F2 pots for focus but no G2 pot. Apple Service Manual implies that G2 voltage is controlled by IVAD and it looks like it is. I think on I2C device 0x46 property 0x11. There's a page on WikiBooks that calls this "Brightness"... it is probably not. I think what the author of that page calls "Gamma" is brightness.
• I think the default value in the sketch by rockyhill sets the G2 voltage too high. I get slight horizontal smearing on my CRT with it. Or the CRT is broken, but the caps seem fine (no obvious leaks).

Ideally someone out there would have to hook up a sniffer to the I2C bus and play around with the display settings panel on a MacOS or OS X install running on the original eMac hardware. My eMac had a fried logic board so I'm out.

Until then I'm reluctant to release a display settings panel like I did for the iMac G3 since the potential to destroy the CRT is too high. The Arduino sketch itself is almost ready to go. If there's any interest in this I can dump it and a crude wiring diagram on my GitHub after it receives some more polishing.

 

[oshimai]

Sorry to bump the thread again. Here's the current state of things and some pictures on GitHub: https://github.com/shuuryou/emac

It is working but it isn't at all polished, I'm afraid.

Next step is to get Linux running to get rid of f***ing Windows 10. 🤮

 

[rockyhill]

Sorry to bump the thread again. Here's the current state of things and some pictures on GitHub: https://github.com/shuuryou/emac

It is working but it isn't at all polished, I'm afraid.

Next step is to get Linux running to get rid of f***ing Windows 10. ?

Great work, this is exciting, I plan on revisiting all of this, it's just been a crazy year with another hobby.
I hope to start making circuit boards for the emac as well but I still need to finish the redesign of
the imac G3 slot loader boards. The chip supply shortage has made it difficult to make something affordable......

 

[dprossner]

shorting pins 23 and 24 to power on), the 12V lines all measure 12V.

With the logic board removed, they drop back to +8.5V. I suspect I need load on a couple of pins kick it into gear.

[edit-edit]

Putting a 5W resistor on the +5V line brought the +12V up to spec, and displayed a picture. Easy as that.

at the risk of outing myself as a noob, I'm trying to do the same thing but I'm having trouble finding pinout diagrams for the logic board connectors. Is pin 23 and 24 in reference to the larger of the 2 logic board connectors? do you have pictures or a source for a pinout diagram? Also, what is a 5W resistor and is it replacing the 500ohm resistor or being added? I've only ever heard of resistors being measured in ohms.

 

[elvisa]

Hi,

I have the same Imac as you, and I would also like to connect a raspberry or others to the Imac screen.
As soon as I unplug the DB15 plug from the Imac, the screen starts up.
Can you give me your cable which allows you to display your laptop PC on the Imac screen?
Thank you in advance.

Cordially.

Sorry for the response delay. I got pinged on Reddit about this too, so pasting my notes in here too.

These notes are purely for the iMac 333 tray load. They do not apply to the slot load models.

To get power, you need to do 2 things - on the main molex power connector, short the "power on" pin to ground. I think I made a typo when I mentioned pins 23 and 24 elsewhere in this thread, as it's only a 20 pin connector. That should be pins 14 (green, "power on") and 13 (black, "ground).

From here, you need load on the power supply. If you can power something from it, great. If not, find a wirewound resistor (I think I had a 1K ohm, 5W one lying around), and use that to connect any of the +5V lines to ground. These resistors will dissipate power as heat, simulating load on the power supply. Once that's detected, the power supply will come out of standby mode and power on both the 12V lines and the high voltage to the CRT. You could also use that +5V to power on an RPi or something if you wanted (make a simple connector into the +5V of a USB cable and power your RPi that way, which would also create load and power on the CRT without the need of the resistor trick).

And then finally, a simple DB15 female (iMac side) to DE15 male (VGA/PC/RPi side) converter. I made one myself using some screw-terminal connectors from AliExpress. The pin connects were as follows:

db15f ---------- de15m
1 - red ground - 6
2 - red signal - 1
3
4
5 - green signal - 2
6 - green ground - 7
7 --- i2c / ID
8
9 - blue signal - 3
10 --- i2c / ID
11 ---- ground --- 5
12 ---- vsync ---- 14
13 - blue ground - 8
14 - sync ground - 10
15 ---- hsync ---- 13

I connected the i2c/ID pins to my RPi's GPIO pins to then read the ID information out. I was attempting to use that to push information back to the CRT to do things like geometry and colour adjustment, but got nowhere (I'm assuming it uses some other protocol).

I've since given up on this project, and reverted the iMac back to its original form, as I needed it to test my RetroNAS project (I needed a real OS9 machine with physical Ethernet connector to test AppleTalk). I'm hoping one day to go back and see if I can do more sniffing on the various serial lines to find out how the logic board controls the CRT. Need some time off work to make that happen though.

 

[devcybiko]

Sorry for the response delay. I got pinged on Reddit about this too, so pasting my notes in here too.

These notes are purely for the iMac 333 tray load. They do not apply to the slot load models.

To get power, you need to do 2 things - on the main molex power connector, short the "power on" pin to ground. I think I made a typo when I mentioned pins 23 and 24 elsewhere in this thread, as it's only a 20 pin connector. That should be pins 14 (green, "power on") and 13 (black, "ground).

From here, you need load on the power supply. If you can power something from it, great. If not, find a wirewound resistor (I think I had a 1K ohm, 5W one lying around), and use that to connect any of the +5V lines to ground. These resistors will dissipate power as heat, simulating load on the power supply. Once that's detected, the power supply will come out of standby mode and power on both the 12V lines and the high voltage to the CRT. You could also use that +5V to power on an RPi or something if you wanted (make a simple connector into the +5V of a USB cable and power your RPi that way, which would also create load and power on the CRT without the need of the resistor trick).

And then finally, a simple DB15 female (iMac side) to DE15 male (VGA/PC/RPi side) converter. I made one myself using some screw-terminal connectors from AliExpress. The pin connects were as follows:

db15f ---------- de15m
1 - red ground - 6
2 - red signal - 1
3
4
5 - green signal - 2
6 - green ground - 7
7 --- i2c / ID
8
9 - blue signal - 3
10 --- i2c / ID
11 ---- ground --- 5
12 ---- vsync ---- 14
13 - blue ground - 8
14 - sync ground - 10
15 ---- hsync ---- 13

I connected the i2c/ID pins to my RPi's GPIO pins to then read the ID information out. I was attempting to use that to push information back to the CRT to do things like geometry and colour adjustment, but got nowhere (I'm assuming it uses some other protocol).

I've since given up on this project, and reverted the iMac back to its original form, as I needed it to test my RetroNAS project (I needed a real OS9 machine with physical Ethernet connector to test AppleTalk). I'm hoping one day to go back and see if I can do more sniffing on the various serial lines to find out how the logic board controls the CRT. Need some time off work to make that happen though.

Hello @elvisa and @rockyhill - I've been following Rocky for about 6 months and just came across this thread last month.

My daughter is 33 years old and is returning to college to get her Psych BS. And her request for her birthday was a iMac G3 as a monitor for her MacBook to aid her studies.

I want to thank both of you for your work. I did the same project as Elvisa with the tray-loading iMac G3, breakout DB-15 connector, and breakout DE-15 breakout connector and got the monitor to work at 1024x768@75 Hz. I still have the logic board plugged in, so I haven't travelled down the path of EVID/IVAD signals or jumpering the power w/ a 10W resistor.

I wanted to share a unique part I found on Amazon while looking for VGA connectors for this project:

C2G 02902 Mac DB15 Male to VGA (HD15) Female Adapter, Beige

Convert your VGA monitor to use with your Macintosh computer. This adapter provides you with a straight-pinned connection between your HD15 (VGA) port and the standard DB15 used with Apple systems. This molded adapter is compatible up to a resolution of 640 x 480 pixels.

www.amazon.com

It's designed to allow VGA monitors to be used on older Macs. I reasoned that the VGA-to-DB15 through connections should be identical to the solution Elvisa found. I purchased one (along with a Female-to-Female gender changer) and It worked first time!

I'm attaching images below. I know I have more work to do if I want it to be a "true" VGA monitor, but this one piece makes for a simple solution if you're satisfied with just 1024x768@75Hz.

Best wishes, Continued Success, and thanks for all the fish!

Greg

 

[oshimai]

Sorry for bumping up a dead thread.

It seems it has become some sort of obsession to stuff a PC into something Apple from decades ago.

I didn't want to destroy a real Macintosh Classic this time since they're getting rare, so I 3D printed its case (modified version of Thingyverse model). It's life-size, but the Apple logo had to be removed because of copyright.

And I'm done screwing around with dodgy CRTs. The LCD is from an old Retina iPad. The driver is from China and can drive it at native 2048×1536 via HDMI.
The PCB next to the PC board is custom for this project because if @rockyhill can make PCBs for crazy things, I can do it too. 😤

Obviously there is a back side to the case as well where the front screws into.

It can press the menu buttons from software. Demo:

I'll throw the STL and Gerber files on my GitHub shortly.

 

[devcybiko]

That's some beautiful work. This thread isn't quite dead, yet. So, I'm grateful for your contribution.

 

[oshimai]

Well, here it is: https://github.com/shuuryou/classicaio

Enjoy and best of luck to anyone who wants to try building it.

 

[deeznuts42069]

Sorry for the response delay. I got pinged on Reddit about this too, so pasting my notes in here too.

These notes are purely for the iMac 333 tray load. They do not apply to the slot load models.

To get power, you need to do 2 things - on the main molex power connector, short the "power on" pin to ground. I think I made a typo when I mentioned pins 23 and 24 elsewhere in this thread, as it's only a 20 pin connector. That should be pins 14 (green, "power on") and 13 (black, "ground).

From here, you need load on the power supply. If you can power something from it, great. If not, find a wirewound resistor (I think I had a 1K ohm, 5W one lying around), and use that to connect any of the +5V lines to ground. These resistors will dissipate power as heat, simulating load on the power supply. Once that's detected, the power supply will come out of standby mode and power on both the 12V lines and the high voltage to the CRT. You could also use that +5V to power on an RPi or something if you wanted (make a simple connector into the +5V of a USB cable and power your RPi that way, which would also create load and power on the CRT without the need of the resistor trick).

And then finally, a simple DB15 female (iMac side) to DE15 male (VGA/PC/RPi side) converter. I made one myself using some screw-terminal connectors from AliExpress. The pin connects were as follows:

db15f ---------- de15m
1 - red ground - 6
2 - red signal - 1
3
4
5 - green signal - 2
6 - green ground - 7
7 --- i2c / ID
8
9 - blue signal - 3
10 --- i2c / ID
11 ---- ground --- 5
12 ---- vsync ---- 14
13 - blue ground - 8
14 - sync ground - 10
15 ---- hsync ---- 13

I connected the i2c/ID pins to my RPi's GPIO pins to then read the ID information out. I was attempting to use that to push information back to the CRT to do things like geometry and colour adjustment, but got nowhere (I'm assuming it uses some other protocol).

I've since given up on this project, and reverted the iMac back to its original form, as I needed it to test my RetroNAS project (I needed a real OS9 machine with physical Ethernet connector to test AppleTalk). I'm hoping one day to go back and see if I can do more sniffing on the various serial lines to find out how the logic board controls the CRT. Need some time off work to make that happen though.

Ive been following your work with the Tray loading G3 and I set up the exact same wiring as you did, I also made a custom DB15 extender that allows me to sniff the i2c Lines, using that I was able to get a dump of the i2c EDID data at startup for the tray loader.

I have included the dump in an excel sheet here with what I got from my logic analyzer.

I am going to attempt to further your research and see if i can get the tray loader to take a 640x480 @60Hz signal, this would allow me to plug it into pretty much any old gaming console.

 

[deeznuts42069]

Ive been following your work with the Tray loading G3 and I set up the exact same wiring as you did, I also made a custom DB15 extender that allows me to sniff the i2c Lines, using that I was able to get a dump of the i2c EDID data at startup for the tray loader.

I have included the dump in an excel sheet here with what I got from my logic analyzer.

I am going to attempt to further your research and see if i can get the tray loader to take a 640x480 @60Hz signal, this would allow me to plug it into pretty much any old gaming console.

Also for anyone with a tray loader. It was pins 23 and 24 on the "atx" connector on the harness that goes into the power supply that I needed to short in order to get the G3 to power on with no logic board. I did not need to put a load onto the power supply either.

 

[LightBulbFun]

I am going to attempt to further your research and see if i can get the tray loader to take a 640x480 @60Hz signal, this would allow me to plug it into pretty much any old gaming console.

the CRT in all iMac and eMac computers are of a fixed frequency design, that is to say they are not multi-sync, they have a fixed vertical frequency, so sadly you cant do 640x480@60Hz, not without modifying the actual analog circuits itself, and at this point your better off just getting a generic 15 inch monitor and mounting its CRT and guts inside the case of an iMac G3

this is also why trying to get Linux to run on an iMac or eMac is such a pain, since by default Linux does not respect the limits of the iMac/eMac CRT and tries to switch to an unsupported video mode so the display blanks out

 

[sharpdad]

Trying to catch up on 17 pages of comments about this idea. Do the circuit boards designed by Rocky work on an eMac? I just picked one up and have been searching furious for the "wikihow" document mentioned elsewhere online (reddit, etc.) that has been lost and now replaced by the far better GitHub repository for the iMac customization. I'd like to try it on this eMac and just wondering if anyone has used the same circuit boards, connectors, etc. on an eMac successfully. Thanks!

 

[deeznuts42069]

the CRT in all iMac and eMac computers are of a fixed frequency design, that is to say they are not multi-sync, they have a fixed vertical frequency, so sadly you cant do 640x480@60Hz, not without modifying the actual analog circuits itself, and at this point your better off just getting a generic 15 inch monitor and mounting its CRT and guts inside the case of an iMac G3

this is also why trying to get Linux to run on an iMac or eMac is such a pain, since by default Linux does not respect the limits of the iMac/eMac CRT and tries to switch to an unsupported video mode so the display blanks out

Yeah I wound up realizing that when I read through some of the earlier pages of this thread. I am not opposed to seeing if its possible to change that fixed vertical frequency and in fact I have a few donor machines with severe issues that are perfect for that task. My thought is that there is for sure some PLL/Clock frequency that I could mess around with, or I can trace the EDID and H/V sync lines back through the analog board and see what I can figure out.

 

[deeznuts42069]

Trying to catch up on 17 pages of comments about this idea. Do the circuit boards designed by Rocky work on an eMac? I just picked one up and have been searching furious for the "wikihow" document mentioned elsewhere online (reddit, etc.) that has been lost and now replaced by the far better GitHub repository for the iMac customization. I'd like to try it on this eMac and just wondering if anyone has used the same circuit boards, connectors, etc. on an eMac successfully. Thanks!

Rocky has a separate GitHub page for the EMAC VS the slot loader G3 so I believe there is some difference?
The documentation mentioned in the readme on the EMAC GitHub is within this link which was taken down at some point.
https://en.wikibooks.org/w/index.php?title=How_to_modify_an_eMac_to_use_as_an_external_monitor

Here is an archived version of that page
https://web.archive.org/web/2022092..._modify_an_eMac_to_use_as_an_external_monitor

Rockys GitHub page with the projects
https://github.com/qbancoffee

 

[Lingwendil]

Are PCBs available to purchase for this project in singles? I don't need five of each...