SM74 Delivery fan wire connection

Discussion in 'Heidelberg Printing Presses' started by narayan, Oct 5, 2018.

  1. narayan

    narayan Member

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    checked the new fan in another connection at center tail side. It spins with reverse speed setting as before. old fan doesnt spin when connected to the connection where new fan was connected. Also new fan spins when +ve and -ve are connected whereas old fan doesnt spin. Does this means old fans are problem? How can all 5 fans be problematic ? May be because of new fan?
     
  2. CHOCK

    CHOCK Senior Member

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    Hi sir
    1) The old fan, the winding internal can be :reheation or open, or burn,and bearings defective =faulty
    2) New one Reverse the wires from the new ones, very simple.
    Now you have a Great conclusion!!
    Enjoy.
     
  3. narayan

    narayan Member

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    Sir can you put more light on reversing the wire for new fan. Point a and b (which you marked). which wires exchanges?
    Thanks
     

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  4. CHOCK

    CHOCK Senior Member

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    is easy.
    Example is you put the red in - and black in +
    Reverse: Red in + and black - o.k ?
     
  5. narayan

    narayan Member

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    After long time i found that the new fan would spin at full speed when pos and neg 24v are supplied and pwm signal is absent. This fan's speed is full when pwm value is 0 and stops when pwm is 255. Wonder if the older fans would spin at full speed when pwm = 255. Anyone can clearify?
     
    Last edited: Dec 3, 2019

  6. CHOCK

    CHOCK Senior Member

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    Interesting issue.
     
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