Hi, I finally got some time to delve into this project and wanted to ask for some help to get this working.

First of all, I would like to thank you for all your efforts in putting together these extremely detailed resources. It is super insightful and inspiring!

The reason for opening this issue is that, like others, I also got stuck on the step where I successfully managed to send the initialization sequence to the ivad board, but the display is still not showing any picture.

Just as a preamble, I'm using an iMac G3 (slot loading), and the screen works properly when connected to the original logic board. Also, I'm not sending the EDID sequence to the computer; however, I believe this shouldn't be a problem at this point.

Test 1:

To provide you with more details about my setup:

• I'm not using the breakout board you've created. Instead, I've wired an Arduino Uno with jumper wires to test the concept and see if I could get something.
• The wiring setup is pretty simple: all wires from the VGA are connected to the J20 connector following your wiring diagram. Apart from the SDA and SCL wires that are connected to the Arduino via jumper wires plugged directly into the J20 connector on the iMac. I double-checked all the wiring a couple of times just to make sure all the connections were correct.
• While you have a pretty fancy setup using SSR and a power button, just for testing purposes, I decided to bypass all of that. This means that I shorted Pin 12 and 10 of the J20 connector to Pin 6 (5V trickle) of that same connector using jumper wires. The Arduino Uno is also powered using the 5V trickle.
• For the Arduino code, I changed the buffer size of the Wire libraries to 128.
• I also uncommented line 136 of the latest Arduino sketch (externalCircuitOn();), which, to my understanding, will initialize the ivad board as soon as I give power to the iMac.
• I'm currently using a VGA to miniDP adapter that connects to an Intel Nuc (my final goal is to implant the Nuc inside the iMac and convert it into an all-in-one Windows PC using the original CRT). However, I also tested this with a Windows laptop that has a built-in VGA out and got the same result as with the adapter.

The result of the first test is that when I give power to the iMac, I can hear the static sound from the CRT followed by a click sound (sort of a relay sound) after a few seconds. If I remember correctly, this sequence of sounds occurred in the same way when using the iMac logic board. However, even after waiting for a long time, no picture was showing on the screen.

Test 2:
I then made a second test where I tried to replicate a makeshift version of the power button input:

• I commented out line 136 in the sketch, so that it would wait for power button input to send the sequence.
• I wired PD3 of the Arduino to 5V trickle through a resistor and used a jumper wire from PD3 that I would manually connect to ground, mimicking the behavior of the onboard power button.
• I also commented out line 180 of the sketch just to make sure that the problem was not related to the lack of detection of the Vsync signal.

After giving power to the iMac, I can immediately hear the static of the CRT followed by the click, even before grounding the "power button" input. Shorting PD3 to ground for a short interval doesn't produce any effect, and as a result, I get the same result as in the previous test where no picture is shown on the display.

So my questions are: Is there something fundamentally wrong with my current MVP setup? If not, do you have any other suggestions on how to troubleshoot this?

Thanks

Have been inspired to try this with an Emac and a Pi4 (no arduino). VGA cable is made and i2cdetect is reporting 46 and 53, as expected. Looking at the emac_ivad_board_init for the arduino and contemplating next steps, any suggestions or pointers?
Thanks!

Hey, I'm wanting to do this with my older, first generation iMac, but it has a two-row DB-15 connector. Still 15 pins like VGA, but with a different layout. Are the same numbered pins the same, or is there a separate pinout diagram for the DB-15 connector?

I am wondering, what are the display formats/timings for the Imac G3? I have a device that takes custom timings, and I want to capture the G3's VGA-Out. Figured you might know this. (I'm specifically trying to capture the 640x480, 117hz mode.

Hello, I've been looking into the ADC Apple Studio Display, model M7768. This is Apple's last CRT, and it uses ADC as it's connector. It's possible to split it back into VGA + USB + Power (+LED +Soft Power), either by a converter or simply splicing the wires. However, the Display will only "boot" if it's connected to a G4-G5 era Mac, as it needs some sort of boot signal.

Now, some known things about this monitor:

• It accepts DDC over USB, to calibrate it. You can audibly trigger the degauss with it.
• It can be woken up even when connected to a VGA/DVI-A port on a proper mac, if the ADC cable is split to it.
• Per /u/crt09, the signal is probably coming over DDC.

Is there any possibility the boot signal this monitor expects is related to the signals these IVAD boards use?

C:\Users\gerar\Downloads\imac_g3_ivad_board_init-master\imacG3IvadInit\imacG3IvadInit.ino:50:10: fatal error: EEPROMWearLevel.h: No such file or directory
#include <EEPROMWearLevel.h>
^~~~~~~~~~~~~~~~~~~
compilation terminated.

exit status 1

Compilation error: EEPROMWearLevel.h: No such file or directory

I don't know if this is the right place to put this, but I'm putting in an order with Digikey and one item is listed as being a non-stock item.

That's the 609-3367-ND vertical connecting header.

Is there another substitute item that can stand in for this one?

I'm not sure if it's just on the Digikey Ireland website which I'm ordering from either.

I have been reviewing the BOMs and there's a part on Digikey that says it's obsolete.
This is the part USA1H010MDD1TE
Do you know another place where I can order it or a substitute part? DigiKey suggest me another component but the substitute has a minimum order quantity of 2000.

Hello, I followed the wiki step by step but something isn't working. I'm trying to understand if it's because some shoddy soldering, some faulty component or rather my Italian iMac G3 that may want a different edid. When i connect a laptop to the vga port on the J20 board, it recognizes a new monitor. As soon as the power chord is connected, the green led on the button turns on and I can hear the cathodic tube warming up. But no image is shown and after a few seconds of inactivity everything turns off. Then if i push the power button, all that happens again, it turns on with no picture just to turn off a few moments later.
Do you happen to have seen this behaviour before? Can it tell us where is the issue in my boards?
Thank you in advance.

Hi, I'm creating this issue to track the problems that I'm facing when interfacing the iMac FP panels to an ATX motherboard. This may be a scenario that other people attempt.

Currently the imac_g3_slot_loading_J22_adapter_board behaves as a relatively simple breakout board for the FP connector, with some nice convenience features like microphone power adaptation.

However, I've noticed some issues when attempting to wire this to an ATX motherboard.

FP LED/Switch board integration

FP Switch

Works fine. However, polarity matters. ATX power switch pins are un-polarized, they just expect to be shorted to power on. In practice they are usually +5V and GND with some inline resistor. This means the polarity has to be measured with a multimeter and motherboard GND must be connected to FP GND in order to not accidentally short +5V to ground.

FP LED

Both power and sleep LEDs have a common ground, and take a +5V input to activate. The LED expects an open-emitter style circuit. However, most motherboards I've found have an open collector design for their LED outputs, where the +5V pin is constantly powered (even while PC is off!), and a transistor switches on and off the ground side of the pin.

This is problematic, because the ground is shared with the FP Switch, which is already tied to motherboard ground. When connected, the LED receives a constant +5V, and also has a constant ground via the FP switch ground, so stays lit all of the time (even when the PC is off).

Solution

Somehow the open-collector circuit from the motherboard power LED pins needs to be adapted into an open-emitter circuit. I think this can be solved by placing a single PNP transistor such that:

• Emitter is wired to motherboard power LED +ve (constant +5V)
• Base is wired to motherboard power LED -ve (open-collector switching ground), probably with an inline resistor (idk I'm not an electrical engineer)
• Collector is wired to FP LED +ve
• Constant motherboard ground is wired to FP GND (or to motherboard power LED -ve via a diode?)

Additionally, the FP switch could be isolated so that it doesn't matter what polarity the wires are connected. Not really sure how to do this without something silly like a relay.

FP Audio

Wiring FP audio channel outputs is simple. iMac FP connector has isolated left and right wires for each jack. Intel HD Audio header has the exact same thing. Jack detection is a problem however.

The iMac FP Audio connector has normally open jack detect switches J1_SW and J2_SW bridged to a common ground.

Intel HD Audio is weirder. It detects what is plugged into it by measuring the resistance between the HD Audio SENSE_SEND pin and reference GND. There is also a SENSE1_RETURN and SENSE2_RETURN pin on the motherboard header, however these are not actually necessary and really just a convenience feature. They're bridged to ground via an appropriate resistor such that when SENSE_SEND is connected to them, it "sees" jack 1 or jack 2 is connected.

Reference: 7.4.2 Audio Jack Detection Circuits, Page 222, Intel High Definition Audio Specification

Solution

In order to adapt the FP Audio connectors to Intel HD Audio:

• SENSE_SEND is wired to J1_SW via 39.2 kOhm resistor
• SENSE_SEND is also wired to J2_SW via 20 kOhm resistor

New adapter board

For ATX integration it probably makes sense to create an ATX interop version of imac_g3_slot_loading_J22_adapter_board which has the additional required interfacing circuity, as well as the pins for ATX power switch, ATX power LED, ATX HDD LED (can be wired to iMac sleep LED), and the Intel HD Audio header pins.

I'm currently learning KiCad so I'll probably eventually take a shot at this, but if anyone wants to jump in first, please please do.

Hello

To make the sketch work in its current state the Wire library needs to be patched in two locations so its buffer size is 128 instead of 32.

I am curious as to why you decided to go with that approach. Did sending the EDID in bursts not work?

e.g. like this (totally untested pseudocode)

/* somewhere in the global scope */ 
// Default buffer size of unpatched Wire library
#define TWI_BUFSIZE 32

#define EDID_LENGTH 128
// (or like this, GCC is hopefully smart enough to optimize it into a constant)
// int EDID_LENGTH = sizeof(edid) / sizeof(byte);

byte edid_chunk_buf[TWI_BUFSIZE];




/* where the EDID is sent to the controlling PC */
int i;
for (i=0;i<EDID_LENGTH;i++)
{
  if (i!=0&&i%TWI_BUFSIZE==0)
    Wire.write(edid_chunk_buf, TWI_BUFSIZE);

  edid_chunk_buf[i%TWI_BUFSIZE] = edid[i];
}

// next 2 lines not really necessary if EDID_LENGTH is always a multiple of TWI_BUFSIZE
if ((TWI_BUFSIZE-i%TWI_BUFSIZE)!=0)
  Wire.write(edid_chunk_buf, (TWI_BUFSIZE-i%TWI_BUFSIZE));

I am currently (again, after destroying the first one last year) trying stuff with an eMac and building on the foundations you painfully figured out for that heavy monster. But since your iMac sketch is the pretty one I thought I'd file this here.

The real pain with the eMac is finding a HDMI>VGA adapter that will attempt to do the insane refresh rates on lower resolutions. That's a different story though.

At first when I click the button it turned on and you heard the electric sound and the green led also turned on, now it doesnt turn on so I supose there is a power issue. Is there anyway i coul use a standard computer PSU to power it?

Do I just need the monitor? or do I also need the power supply?
How do I know if my iMac is slot-loader or tray-loader?
I saw in the wiki a link to order speakers, Can I use the original ones?

I have managed to get the screen to work in the raspberry version but it comes out with violet tones. I'm trying to adjust the green but I'm not getting any results.

I have a question about the use of the relay on the J20 board. Is there a reason the PFW and LPIACT signals can't be pulled high/low by the microcontroller directly (high current requirements?) or was it just easier to combine those signals and the led into a single switch?

Hi all,

I should preface this by noting I am a complete amateur and likely am missing something obvious but I would love some help.

Everything is set up, but when I turn on the power the screen remains black. There is a green light indicating power and I can hear static when the CRT is turned off and on. But no image and the computer cannot detect it at all. I did make sure to comment "externalCircuitOff()" under when "vsyncDetect is 0".

Info: The iMac works with the original logic board, I am not using an VGA to HDMI adapter (though I will try it) and I have tried a couple different cables and two different PCs.

Any help would be appreciated. Thanks for your time.