Power Supply Siemens Logo 24V

Discussion in 'General Electronics Chat' started by albertitojudio, Oct 24, 2013.

  1. albertitojudio

    Thread Starter New Member

    Oct 24, 2013
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    Hello, I have 2 siemens logo power supply 6ep1332-1sh42 with the same problem, it have a led that indicate 24V ok, when I switch on the power supply not start and I can hear a 12khz noise, I switch off and after 2 seconds the led goes on, if in this moment or until the capacitor discharge switch on it, the power supply start and there is no noise.
    I have checked all capacitor and diodes and all ok, anything can help me?
     
  2. #12

    Expert

    Nov 30, 2010
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  3. #12

    Expert

    Nov 30, 2010
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    Possibly going into self protect because of a start surge into bad output capacitors.
    Does it have any load connected externally?
     
  4. albertitojudio

    Thread Starter New Member

    Oct 24, 2013
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    Hello, there is no charge in the output, with charge do the same. I have check the bigger capacitors and all ok.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Replace any small electro caps near the optocoupler and heatsink. :)

    Photos of the PCB are well worth the effort too.
     
  6. albertitojudio

    Thread Starter New Member

    Oct 24, 2013
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    Only have 4 electro caps, I have check all and are ok.
    The NTC is ok too.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    How did you "check all" the caps? Small caps cost a few cents and always age and get worse with age, especially if they are near something hot.

    The best solution for most people is to replace them as the "check". :)
     
  8. albertitojudio

    Thread Starter New Member

    Oct 24, 2013
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    Hello, I change a 4,7uf 100v capacitor and all ok, the capmeter show 5uf, i don´t know why is fault but I change it and all ok.

    Many thanks
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Great! :)

    The cap fails by drying out, so it can still measure close to the correct uF value, BUT it's ESR (Equivalent Series Resistance) goes right up.

    Basically that means the cap works mostly ok at low frequencies, but at high frequencies (like in your PSU) the cap fails.
     
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