Macbook 820-2279-A fan not spinning

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  • tony359
    Badcaps Veteran
    • Oct 2018
    • 259
    • United Kingdom
    #1

    Macbook 820-2279-A fan not spinning

    Hi all,

    I have this old macbook which I am trying to repair for nostalgic reasons
    The fan does not spin until the MB overheats and shuts down.

    The fan gets 5V but there is no PWM on pin 3. The same with the fan unplugged, no PWM on pin 3. The fan shows some glimpse of activity every 5 seconds. Sometimes it spins for half a revolution and that's it.

    From the schematics (obtained from this forum, THANKS!) I see there is a mosfet getting signal from the SMC. The mosfet gets 3.3V but there is no input - well, there is 3.3V. I removed the mosfet to see if I had anything from the SMC but I still have nothing. One thing I noticed is that with the fan connected I see 5V on the PWM pin, coming from the fan. Is the PWM supplied to the fan as a square-wave signal or is the driver pulling to ground the signal coming from the fan?

    I tried powering the fan "manually": I supplied 5V, GND and I plugged the PWM to a signal generator but besides making some noise depending on the frequency I sent, the fan would draw 100mA, show a glimpse of activity and do nothing.

    Before I buy another fan, I am puzzled about that PWM signal not showing on pin 3 even with the fan disconnected.

    Any ideas?

    Thanks!

    Click image for larger version Name: pwm.png Views: 431 Size: 138.5 KB ID: 3545716
    Tags: None
    • tony359
      Badcaps Veteran
      • Oct 2018
      • 259
      • United Kingdom
      #2
      Just to complete this thread, it was just a faulty fan. A working fan works when supplied with 5V. And it works in the MacBook!

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