Apple G4 AcBel PSU - blink failure mode

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  • ChairmanJones
    New Member
    • Apr 2021
    • 2
    • United States
    #1

    Apple G4 AcBel PSU - blink failure mode

    I have an AcBel PSU that was exhibiting the typical failure mode with the single blink light then no power on.

    I started the rebuild with the shotgun 12, same issue. Fuse has continuity. My question is, has anyone narrowed down the cause to specific caps or is it a case of replace them until it works? What caps should I be replacing next?
    Tags: None
    • PeteS in CA
      Badcaps Legend
      • Aug 2005
      • 3578
      • USA, Unsure of Planet
      #2
      Re: Apple G4 AcBel PSU - blink failure mode

      Some generic questions:

      * Does this P/S have active PFC? If it does, what is the voltage across the big electrolytic capacitor? If it does and that voltage is ~165V, the PFC is not working and that is where to start your troubleshooting.

      * If it does not have active PFC or the voltage across the big electrolytic capacitor is something like 390V, do you have good 5V Standby? If not that is where to start your troubleshooting. If 5V Standby is also OK, then the problem is in the main inverter or output circuits.

      I'm not familiar with the specific power supply, but these are quick ways to localize where to look for problems.
      PeteS in CA

      Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
      ****************************
      To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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