Quirk about the ADC Connector

I started having problems with the ADC display using the adapter I built. It worked fine for quite some time then the display started to shut itself off and not be recognized by the system. Sometimes it would work to plug the cables back in.

At first I thought it was the power supply I was using. I don't have specs on it, but the problem surfaced when the temperature climbed. The computer area was hovering around 90°F, and I assumed the power supply was sporadically failing. I bought a new-to-me 24V 1.8A supply for my 17" monitor (I think that might be a bit on the low-side, but it was only a couple dollars at a thrift store.) The problem persisted almost immediately. So I figured the monitor might be fried.

The ADC connector shield is loose.

The ADC connector shield is loose.

I had noticed the shield on the ADC connector on the board was not connected to the ground very well. I didn't think much of it — after all, there were half a dozen ground wires already. But on a whim, I thought I'd add a couple dabs of solder and give it a solid connection to the pins soldered onto the board. Surprisingly, that did the trick. So far it's been 2 days and the monitor has not flaked out! It may be the power supply is on the low-side to begin with (24V) and without the additional ground of the shield, the voltage drop crept too high in the other wires for the monitor to function.

ADC connector shield.

ADC connector shield.

In any case, if you are observing sporadic problems where the monitor would shut off, apparently losing power, check the shield on the ADC connector and make sure it has a solid ground.

Solder added to ADC connector shield.

Solder added to ADC connector shield.

Update August 7, 2013: Not so fast. I am still having problems where the monitor will switch off and not come back on. Most recently, I had to unplug the power for 15 minutes as well as the connection to the computer before it came back to working. I'm not sure what it is, but the ground is not the only fault going on here …

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9 Comments on “Quirk about the ADC Connector”

  1. Tom Grim says:

    I bought several of those ADC connectors, and it looks to me like there should be a screw holding the shield to the threaded part that is mounted to the circuit board, where you would find the retaining nut on a DVI connector. I just looked at my G4 mac, and it has screws in those holes to mount the ADC connector to the back panel of the video card.

    Also, I wonder if there might be a ground loop problem with tying all the return leads together at the adapter.

    Finally, do you have part number and source information for all the connectors on the board? I have the ADC connectors, but I’m concerned that I will find that the others I choose may not fit the circuit board.

    • I'm not so sure about a ground loop as only the power ground carries any substantial current.

      The parts I found are:
      ADC: Surplus Sales of Nebraska (#CPC?)
      DVI: Molex #74320-9014 from Mouser (#538-74320-9014)
      VGA: Norcomp 181-015-213R171 from Mouser (#636-181-015-213R171)

  2. Jim says:

    Hi Jason:
    I started having the same issue with my Cinema Display, randomly turning off.

    I bought a second apple adc to dvi adapter and the newer one did it too. I borrowed a friend Cinema Display and it does it with both adapters.

    Have you found any new information out about the cause?

    Please advise, THX, Jim

    • So far no further information. I suspect a combination of ambient temperature above about 27C and a power supply that is marginally providing enough power.

      • Jim says:

        Thanks Jason, I thought heat might be the cause as well. So I attached two fans to the power supply. Still blacked-out over time.

        I'm starting to think it's where the APC connects to the power supply. I'm sometimes able to get it working again if I just unplug and replug-in the monitor at the power supply.

        But very odd that it's happen on two different monitors and two different APC adapters.

        • Jim says:

          Follow-up!
          Definitely an issue with the APC connector for me.

          The connector on the end of the monitor cable has the ability to be bent between 0 – 90 degrees. If the cable is not perfectly straight the monitor will black-out over time or power-up when the MBP is off.

          Neither phenomenon happens or repeats when the monitor cable is perfectly straight. Inhave verified this with separate monitors and separate APC/DVI adapters.

          Hope this helps you…

          • Very interesting. To be honest, I thought I had it licked with the better shield grounding, but then it crept back when the temperature rose again, so I was examining a coincidental relationship, not a causal one. While it's plausible that bending the cable is the cause—perhaps through strain on the connector or shifting the internal cabling (capacitive coupling between wires?)—it's still just a coincidental relationship at this point. Further, if this were the case, it would have happened with Macs with built-in ADC ports, and I haven't done any research into that.

            Edit: I did some research and found a discussion from 2005 on the Apple Support Community. It looks like the same kind of issue, although then people were blaming it on defective monitors—particularly the CFL inverter board. The discussion never comes to a solid conclusion, fix, or workaround. I suspect all the ADC monitors flake out eventually and just stop working, and since mine was bought used with an unknown history, I'm starting to lean to that.

          • Jim says:

            I have 2 separate monitors with 2 separate ADC adapters, mixing/matching make no difference. Still blacks out over time.

            The 2005 discussion gave me an idea.. I was always fixing the issue at the adapter. I disconnected everything, including the adapter at my MBP. Put it all back together starting at the AC outlet. It's been over 18-hours and no blackout…

  3. Jim says:

    Hi Jason:
    One other thing for you to try, at the connector of the monitor cable. Remove clear plastic sleeve that's between the buttons and the pins, by pulling straight off. Gently pry open the plastic housing encasing the pin housing and set it aside. Should come apart easily.

    With some electrical contact cleaner or degreaser and a small nylon brush clean the monitor connector pins. Let dry completely. Leaving the connector as reconnect it to the DVI/ADC adapter. Test your system to see if it blacks-out.

    Mine has not black-out in over a week now. I'm thinking of not reassembling the plastic shroud and leaving as is…


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