iMac G4 20-inch Skull Canyon NUC

Discussion in 'iMac Mods' started by superslurt, Jun 5, 2016.

  1. superslurt

    superslurt

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    Jul 30, 2016 at 4:21 PM #11
    superslurt

    superslurt

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    Thank you for kind words, Esterhernd. I knew this wouldn't be a walk in the park, so I am OK with the issues so far. Hopefully I will be able to work them out.

    I have been using it every day now for a week, and it performs really good. That's good enough for me at the time being. A lot of things could have gone wrong that hasn't!
     
  2. Jascha

    Jascha

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    Jul 30, 2016 at 9:03 PM #12
    Jascha

    Jascha

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  3. superslurt

    superslurt

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    Aug 2, 2016 at 10:14 PM #13
    superslurt

    superslurt

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    Thanks for the tip, Jascha.

    But today I discovered something. The iMac had more of these "seizures" than usual, and I got annoyed.

    Screen Shot 2016-08-02 at 23.11.17.png

    So I took the machine by its neck, and shook it. The screen was clear! The next time it happened I shook it again, and it worked. So each time there's some sort of noise on the screen, it helps to shake it, at least until it starts again.

    Doesn't this mean that there is a problem with the connection somewhere? Thinking about opening it up tomorrow to do some experimentation...
     
  4. InsaneCultist

    InsaneCultist

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    Aug 6, 2016 at 1:49 PM #14
    InsaneCultist

    InsaneCultist

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    When I was wiring my 20 inch G4 display, I had a horrible issue with artifacting. Turns out it was the adapters I was using. Tough to tell from your pictures, but it looks like you're using Ersterhernd's method of a DVI to HDMI adapter, then converting to whatever output is on your NUC? My issue was remedied almost entirely by using a unified cable. I ordered a Startech miniHDMI to DVI cable (no adapter, all wiring) and have had little to no artifacting ever since, even on my HD5000 GPU.

    EDIT:

    In my hype to help you out, I forgot to mention how beautiful your iMac turned out. It really is a very nice project - always nice to see the love for the G4s.
     
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  5. superslurt

    superslurt

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    Aug 7, 2016 at 1:05 PM #15
    superslurt

    superslurt

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    Major breakthrough today!

    I wanted to fix the following:
    1. Graphical artefacts
    2. Random (and not so random) sudden shutdowns
    3. Fan noise

    # Problem 1 - Graphical artefacts

    As my last post showed, the artefacts got gradually worse. I was convinced it had to be the wiring, since the artefacts would go away if I shook the machine. Therefore, I opened the machine and added a great amount of hot glue on all the open connectors, including the TMDS-DVI-mod (just as you did, Insane Cultist) and all the other connections to insulate. After that, I added some layers of electrical tape. I then mounted it with velcro to the underside of the PSU.

    IMG_0823.JPG Screen Shot 2016-08-07 at 13.37.46.png

    When I tested it, the iMac gave me this:

    IMG_0827_1.jpg

    I then tried to connect my MBP to the screen, and it wasn't able to show anything at all. Totally black. I then decided to unplug the 90 degree HDMI cable, and connect another one I had laying around that I know is of good quality.

    Screen Shot 2016-08-07 at 13.47.06.png

    And voilá, a perfect artefact-free image.

    The only "problem" is that the cable is 1,5m, and I do not have a shorter one. I decided I'd try to coil it up inside, and it was a really tight fit.
    It has now run for several hours, and haven't had a slightest hint of artefacting :headbang:



    # Problem 2 - Sudden death


    The random shutdowns had gradually become more severe. Especially when running games, it would simply shut off.
    These were the patterns I noticed:
    • It consistently shut off when playing the game Dreamfall or Tomb Raider (2013)
    • Sometimes it would shut off at random with no load
    • It didn't seem heat related. The hottest this machine have been is 80 degrees celcius (104 farhenheit) under heavy load. When browsing the web and watching videos, it's usually 40 degrees celcius. (175 fahrenheit).
    • It has never shut down during a benchmark, and I have seen the CPU hitting the wattage limit on HWMonitor (45w?) several times, and it has not shut down.
    To further test whether it is hardware related or software related, I installed Ubuntu on a USB stick. It stayed on all the time, even when playing Dreamfall and Tomb Raider. I also tried to put the NUC into "Low power mode", but nothing changed. To remedy it, I played around with the SMBIOS settings, but nothing helped.

    Despite my tests, I still had a bad feeling about the internal PSU, and as Rehabman pointed out, it does sound sketchy running everything on the poor internal 190w PSU. Therefore, I decided to throw out the 19v upconverter, and install the original 120w power brick that came with the NUC.

    IMG_0824_1.jpg

    To make it fit, I removed the DVD-cage completely. The power chord is wired into the original cables, after the clip. I did this to be able to seperate the bottom and the cage in future upgrades.

    It was a major success! I have thrown a lot of challenges at it (benchmarks, games and so on), but it has not died on me yet. An unexpected bonus was that the "bird tweeting" produced by the machine stopped. I thought it came from the inverter, but obviously it must have come from the PSU. The "hard drive ticking noises" that I have complained about are also gone.



    # Problem 3 - Fan noise


    My first impression of the fan was that it wasn't that loud. But after using the machine for some weeks, I realized that it was actually quite noisy. It had a high pitched noise relative to the fan rpm.

    To remedy it, I simply took it out of the cage, pulled of the sticker and the rubber seal, and applied generous amounts of sewing machine oil.

    Screen Shot 2016-08-07 at 14.01.37.png

    Then I spun the fan to spread the oil, and resealed it. I used some extra tape just in case, since the fan is mounted upside down. I don't want oil dripping down on my NUC. If you are planning to this, do not use WD-40. It will have the opposite effect after a short while.

    Now the fan noise is a lot better! There are probably fans that are even quieter than this, but this is more than good enough for me :)

    So, to conclude, it has been a very productive day (though my wife doesn't agree) :lol:
     
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    Last edited: Aug 7, 2016
  6. MacTester57

    MacTester57

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    Dec 30, 2016 at 6:49 PM #16
    MacTester57

    MacTester57

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    Cool!

    Well done.

    I assume, that the noise comes from the old PSU, which may have weak capacitors. Is the green/yellow earth wire properly connected to the metal part of the dome?

    MacTester
     
  7. superslurt

    superslurt

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    Jan 1, 2017 at 7:40 PM #17
    superslurt

    superslurt

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    julien7895: I am happy that you liked my project!

    I believe that changing the LCD is definately possible, but it would require a lot of work. First you would have to install and make room for the new inverter. The original inverter will most likely not work very well with a different monitor. And since the original inverter is specifically designed to fit inside the iMac, the unoriginal one will probably not fit. Therefore you would have to fit the inverter inside the dome, and run all the necessary wires through the neck (which might be hard to do, considering how tight it is). Some displays also get visual glitches when you have to run extra long wires.

    Then theres the LCD case and bezel. You would either have to make some mounts/brackets, or just hack it with hot glue or something. Furthermore, the new LCD might also be to thick to fit between the case and the bezel, but I guess a newer display probably will be thinner.

    Have you seen the 20" display in real life? I believe that if you get a screen in good shape, it's still very good, even by todays standards. I am picky when it comes to screens, but the 20" looks great. It's the same display used in the 20" Cinema Display. I would use the original first, and then ask myself if I really needed a 1080p screen.

    Good luck either way :)

    PS: Sinoneptune put a 16:9 display in his iMac G4, but he had to do a lot of work in making a new case and bezel...

    Mactester57: Thanks! The noise was definately the PSU, probably too much strain. The ground is connected at the exact same place as originally designed, so I assume it is OK.
     
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    Last edited: Jan 2, 2017
  8. Lukasguy

    Lukasguy

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    Apr 5, 2017 at 3:49 PM #18
    Lukasguy

    Lukasguy

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    I've read you used a G5 20" lcd instead of the normal one, are these lcd's the same or what's going on?
    I believe I've got a broken lcd here and want to find a new one to replace it
     
  9. superslurt

    superslurt

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    Apr 5, 2017 at 4:08 PM #19
    superslurt

    superslurt

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    G5 displays are a lot cheaper, and works just as good. :)
     
  10. Lukasguy

    Lukasguy

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    Apr 5, 2017 at 6:34 PM #20
    Lukasguy

    Lukasguy

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    Do you have the part number/ name of this lcd panel?
    I'm certain now that mine is broken, I checked all the connections with a multimeter on the DVI connector and the connector that plugs in the lcd.
    Otherwise the monitor is found with the correct resolution and the backlights turn on but no image.

    Edit: I've found this screen name: LM201W01 (A5)(K2). Is this the correct one?
     
    Last edited: Apr 5, 2017

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