Apple Display Connector Adapter Board

(See also additional blog posts about the ADC Adapter Board; all Paleocord adapters.)

I picked up an Apple Cinema Display at a garage sale for a few bucks. I noted that it had no apparent power connection, but the cable terminated in what appeared to be a DVI connector. Once I got it home, I realized that wasn't the case. Not only was the connector not DVI, but it was a proprietary connector type called the Apple Display Connector (ADC) that carried digital video data in DVI format along with USB and power. Apple used it on late G3 and G4 Macintosh computers with an ADC video card. Several companies made adapters that supplied power, but they are rare these days and often expensive, such as this Apple-branded one on Amazon.

I looked for several options and found this DIY ADC Adapter article on Tony's Look, It's Another Blog. He hand-wired an adapter that worked, but I wanted to do it tidier and with a circuit board; also to improve my skills. Alex also wired a circuit board that he sells on BatchPCB, but in a related Instructable, he notes that he updated to version 1.1 to correct a wiring bug, yet the BatchPCB board appears to say "1.0" on it (I tried contacting him but without success.) In addition, his version did not include VGA which I wanted to add, and I wanted an Altoids-tin ready board.

Oh, and I wanted to experiment with Open Source Hardware (OSHW) so the project is open-source. See the blog category for updates.

Update 2012-Apr-3: (OK, I'll make an exception.) I made a final version of the board that corrects the inconsequential ground wire error and you can order it from BatchPCB here.

Update 2013-May-31: By popular request, I updated the Gerber files for OSHPark which replaced BatchPCB. Here's the ZIP archive with the Gerber files. A more verbose description is in the blog.

Update 2014-Jan-16: OSH Park added a feature where you can share your designs, so now you can find it here.

Update 2014-Apr-9: I've had a couple requests for the part numbers to get this thing all assembled. The LEDs and resistor are optional and only for power indication, except for the 1K resistor which tells the monitor to turn on (I think … it's been a while.) The diode is also optional; it's only there if power to the ADC was needed from USB (which I guess it's not.) The capacitor must be at least 30 volts and can be as small as 10µF up to about 100µF. The VGA port is optional, but it will connect correctly to the DVI so it should work as a DVI-VGA adapter (if your DVI port supports analog, which most don't anymore.)

Update 2022-Dec-9: I completely forgot that I had also created a PDF of the schematic which can prove quite useful if you're trying to figure something out.

I'm not going to specify a source for LEDs, capacitors, resistors, and diodes—you can find them at any store that sells electronic components, but here's the rest of the parts. Note that you can also use a standard USB-B socket (all the popular ones I've seen have 4 pins in a square pattern; if the shield doesn't fit in the holes, it can be omitted or just bent over and surface-soldered in place). If you must have a complete materials list, here's the sources:

Description (Manufacturer)Supplier
ADC connectorSurplus Sales of Nebraska, #(CPC)DV3R035N11
DC power socket (Kycon)Mouser, #806-KLDHCX-0202-A
DVI connector (Molex)Mouser, #538-74320-9014
MicroUSB connector (Molex)Mouser, #538-105017-0001
high-density DB-15, female, right-angle (optional) (Norcomp)Mouser, #636-181-015-213R171

I was also able to create a Project at Mouser that has all the parts from Mouser. You'll still need to find the ADC connector at Surplus Sales of Nebraska.


22 Comments on “Apple Display Connector Adapter Board”

  1. Sean says:

    I'm curious: You mentioned the 1.0 vs 1.1 versions of the Alex_MP PCB; I ordered what I guessed would be the most current version – but mine also said 1.0 – but I received 2 boards. I would not have a clue how to design the layout, or what the electrical rules are, but since you have also designed your own, maybe you can shed some light on a problem with the Alex_MP board. I see where the USB needs to go to the ADC pins 21, 22 and 23; however, just because 22 and 23 say "Data-" and "Return" respectively, that doesn't mean that they can occupy (intersect) the main ground path, correct? Wouldn't that explain why the USB won't work? It seems like an error that would be easy to make – that is, if it is actually an error? What do you think? Cause this is really driving me crazy. My display does work (finally) but the USB does not. I realize you didn't design the board in question, I just thought you may have run into this issue in your design? Again, I really don't know if it is the problem.

    • I'm not sure what the Alex_MP board is like since I never bought one. If I remember correctly, USB has a differential data path, so you can't connect either of the data pins to ground nor +5V. ADC pin 23, "Return" is the 0V reference for the 5V power, so it's at the same potential as electrical ground and can safely be connected.

      ADC pin 21 should be connected to USB data + and pin 22 should be connected to USB data – (and not to ground). On my board, that's the way they are connected and that permits the USB hub feature of my monitor to work (although as I note, it's not "seen" by the system, not even in Apple System Profiler.)

  2. Frank A says:

    Interesting, but by the time I order the PCB+ parts, figure up a small box to put it all in, power supply … might as well find a used Apple converter @ $ 35 ~40 :-(

  3. Andre says:

    hi how to use a diode near the port usb ?

    • The diode is a way to allow USB power to get to the display adapter without any power that may be at a connected VGA or DVI port to be back-fed into the USB port on the computer. The board needs 5V to come from somewhere to supply current to the "Hot Plug Detect", DVI pin 16.

  4. Carey says:

    Hello Jason,

    First off, I want to say thanks for the great resource you're providing… I know that you say the diode is "optional", but what type of diode would be needed? I have the rest of the parts and want to finish assembling the adapter.

    Thanks again.

    • If you want a specific number, get a 1N4009 (although any 1N400x will work equally well if you happen to have that.) The USB isn't supposed to supply more than 500mA, and I if anything is going to draw power from that point I would not expect it to be more than 100mA, so any diode good for 750mA+ will be plenty fine which is pretty much any of them.

  5. Paul Witek says:

    I know this is resurrecting an ancient project, but when you note that the VGA is connected to the DVI connector – is it also connected to the ADC connector? As in, could this be used to drive one of Apples ADC crt monitors that used VGA signals via ADC?

    • It has been a long time since I looked, but I believe that is the case. I never had such a monitor so I couldn't test it, but the VGA signals present on the DVI connector are wired to the ADC connector and to the VGA connector. They are all connected in parallel, so it should be possible to wire the ADC and VGA connectors and get VGA signals into an analog-compatible Apple monitor.

  6. Roberto Rossi says:

    I was given a 22 "Cinema Display with the ADC connector: did you have an ADC to DVI pcb available?
    Thanks in advance.


  7. Budi says:

    Hi jason, i really like your posting diy. I have an old apple display studio too, and its really hard to find the connector parts in my country, can you help me out please…can i purchase all parts from you in one package? Please let me know thank you. (

  8. KPN says:

    In 2023, I am still trying to resurrect this ancient connector. Wish me luck

  9. KPN says:

    What if I use external GPU connector and graphic card with ADC connector (like from Power Mac G4)?

    • If you have an ADC-output graphics card, it should work with the monitor. My experience was that the adapter board was not ideal in keeping the monitor on: I'm not sure if there was other signaling that did that, but I didn't find anything while I researched it.

  10. KPN says:

    About the 24V DC POWER SUPPLY
    How much current is needed (is 2 A enough?)

  11. I couldn't say. My monitor is a Studio Display and it says it needs 24V at 1.75A. Check the back of yours.

  12. KPN says:

    Hi! I did build the connector and it worked with my PowerMac G4 (using VGA). But it do not work with my Macbook Air M2.
    Just curious, why it did not work with modern mac? Or do I need to install sort of drivers or adjust some settings.

    Thanks in advance, Jason

    • I think modern machines dropped the analog output of VGA (and if I remember right, it's not even available on HDMI, only DVI.) Conversely, I'm pretty sure some of the old monitors only accepted VGA and not digital.

  13. AP says:

    I was able to get this to work with an Apple ADC CRT.

    First I gathered the parts. Don't go doing what I did and get 10w resistors. 1/4 w resistors were absolutely fine and the right size.

    I didn't use any of the LED stuff. I used the parts listed (different DVI connector, they didn't have one listed)

    – DVI: Mouser #538-74320-9010
    – VGA: Mouser #636-181-015-213R171
    – ADC: DV3R035N11 (Surplus Sales of Nebraska)
    – USB: #538-105017-0001 (Untested, not sure if I soldered it correctly)
    – DC Power: Mouser #710-694106301002 (Wurth Elektronik) (Higher Power rating as it's a CRT)

    1N4004 diode (Jason says 1N4009 but I didn't have)
    1,000 OHM 1/4 axial resistor (best quality possible)
    50v 100uf Capacitor: Mouser #647-UBW1H101MPD1TD
    35v 100uf Capacitor: Mouser #647-PLX1V101MDL1TD

    Both worked. I would use any nichicon (Jason recommendation) with 35-50V with 100-150uf rating.

    LHV-24050 Power adapter 24v 5A. (Same power ratings should work, this one had right size plug. You may want to order the correct size plug from mouser)

    Soldering was not as bad as I thought it'd be. I did two boards. You will definitely need flux. I used chip-quik smoooth-flow something or other. I also had alcohol, toothbrush, and paper towels handy to clean up extra flux. What a mess!

    Then I tested them. They both have the same issues.

    1: As others have found, it will not display without a boot signal from a PowerMac. Intel macs didn't work.

    2: I have a PowerMac G4. It didn't come with ADC. I put a card with ADC in it, but the ADC port doesn't work with the monitor. However, when I plugged it into the VGA port, before booting (with the ADC adapter) it worked.

    3: I was then able to plug it into the intel mac, and it worked.

    4: I tested two intel macs, with both boards. They both have only the 2 resolutions that others have had. They both have a green hue to everything. The PowerMac had the same green hue I believe. I will do more testing though.

    5: I didn't test USB. It was not required for the display to turn on.

    The things I will try to resolve, and would appreciate any hep in, are:

    A) The green hue. (I'll try WinACD, unsure never used it.

    B) Needing a PowerMac to boot. It must be some VGA signal, but I wouldn't know where to start.

    Thanks Jason for your advice and for designing the board.

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