Recent content by Georg3

  1. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    Thank you very much again! Battery powering it was the most important thing for me. When I have free time I have to fix the other iMac, the one I started experimenting with and shorted out. As you suggested I'll go through the resistors on that data line to find out what is causing the "AC/DC T2...
  2. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    @2informaticos YOU ARE A GENIUS!!! The NPN transistor is giving the logic board the temp readings so it is not missing the 7-pin data cable, which means I can replace the original ACDC power supply with a DCDC supply so it can be battery powered!! :)
  3. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    Thank you. I will test this on Friday and I hope everything will go well.
  4. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    @2informaticos can I just double check if I understood you correctly that I should solder the NPN transistor onto J6901 in a way that B+C are on PIN-5 and E is on PIN-4?
  5. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    If I understand you correctly I solder B+C to PIN-5 and E to PIN-4 of J6901 and that should make the logic board think that the PSU temp sensors are connected as they should be even if the 7-pin data cable is disconnected? If I don't have access to any donor MacBook or iMac boards can I buy an...
  6. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    Thank you very much for your detailed reply @2informaticos I really appreciate it. Out of curiosity I've checked the "iStats menu" sensors readings after disconnecting the 7-pin PSU "data" cable and I got the same readings as in my previous comment (comment #29) when the 7-pin cable was...
  7. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    @2informaticos as you suggested I have replaced that chip with a new TMP423B from DigiKey. Problem still exists, CPU fan is spinning up to maximum speed, like when pins 4 & 5 were missing, even though the 7pin ACDC data cable is connected. This is what has changed now that I have replaced the...
  8. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    OK, thank you, I'll buy one and let you know when I've changed it.
  9. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    Both lines to ground are 0.696V, then reversing the multimeter leads produces open line.
  10. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    Strange but everything seems to roughly in the right place but there are some interesting differences. I have probed through and I've create a large photo that I have colour coded to show what is connected to what, you can download it here (the forum didn't let me upload it here because it was...
  11. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    So it is somewhere else then, right? I will have to probe through and find where the J6901pin 4 & 5 lead me... hopefully I'll find it quickly. Do you have any advice how to trace them quicker?
  12. G

    iMac 2017 (18,3) fan on max loud, cpu on max

    I've measured L5610/11 they are both 0.9 ohm. That means they are OK? The actual logic board is a bit different than the boardview. The main difference is the IC that is where U5600 should be only has 8 pins instead of 10 as on the boardview. I have attached a photo of it. Am I looking at the...
Top