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E3500 Power/Cooling Module Fuse?

Discussion in 'Sun Hardware' started by pretzel, May 24, 2012.

  1. pretzel

    pretzel Guest

    We have an E3500 that is, of course, long past EOL. However, we still
    use it as a test box. Recently, it developed a failue of one of the
    Power/Cooling Modules. We were able to replace it with another PCM
    from a bone yard E3500 (which the current one is on its way to
    becoming, it would seem).

    The properly functioning PCMs display a solid green power indicator
    LED, and a non-lit amber service indicator LED. In the malfunctioning
    PCM, both LEDs were entirely off. The E3500 Reference Manual states
    that that condition (Off/Off for Power and Service LEDs) means, "No AC
    input".

    Now, when we move the defective PCM around in the various slots, it
    always has unlit LEDs, and the other two PCMs always have a properly
    lit green LED, and an unlit amber LED. In other words, there is AC
    available at all three of the PCM positions in the chassis. Hence,
    the AC must be interrupted in the module, someplace.

    That situation might hint at the possibility of a blown fuse. If so,
    we wonder if the PCM might be "brought back to life" by the mere
    replacement of a fuse.

    A brief inspection of what is visible by removing the sheet metal
    shrouding of the PCM does not reveal an obvious or accessible fuse.

    Is anyone familiar with this old hardware, and able to say whether the
    PCMs in the E3500 have a fuse that might be replacable?

    Alternatively, might anyone have an opinion on the significance of 2
    dark LEDs (= "No AC input"?

    Thank you for any comments.

    DG
     
    pretzel, May 24, 2012
    #1
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  2. pretzel

    Guest

    On Thursday, May 24, 2012 2:43:54 PM UTC-8, pretzel wrote:
    > We have an E3500 that is, of course, long past EOL. However, we still
    > use it as a test box. Recently, it developed a failue of one of the
    > Power/Cooling Modules. We were able to replace it with another PCM
    > from a bone yard E3500 (which the current one is on its way to
    > becoming, it would seem).
    >
    > The properly functioning PCMs display a solid green power indicator
    > LED, and a non-lit amber service indicator LED. In the malfunctioning
    > PCM, both LEDs were entirely off. The E3500 Reference Manual states
    > that that condition (Off/Off for Power and Service LEDs) means, "No AC
    > input".
    >
    > Now, when we move the defective PCM around in the various slots, it
    > always has unlit LEDs, and the other two PCMs always have a properly
    > lit green LED, and an unlit amber LED. In other words, there is AC
    > available at all three of the PCM positions in the chassis. Hence,
    > the AC must be interrupted in the module, someplace.
    >
    > That situation might hint at the possibility of a blown fuse. If so,
    > we wonder if the PCM might be "brought back to life" by the mere
    > replacement of a fuse.
    >
    > A brief inspection of what is visible by removing the sheet metal
    > shrouding of the PCM does not reveal an obvious or accessible fuse.
    >
    > Is anyone familiar with this old hardware, and able to say whether the
    > PCMs in the E3500 have a fuse that might be replacable?
    >
    > Alternatively, might anyone have an opinion on the significance of 2
    > dark LEDs (= "No AC input"?
    >
    > Thank you for any comments.
    >
    > DG






    Replying to own post...

    Answer is, Yes. There is a 250V 10A fuse. It is neither readily visible, not easily accessible. obviously not intended to be field replaceable.

    I wonder why.

    But, can be done, if one is determined and persistent, and can get fingers in to remove a molex connector that contributes to fuse hiding.
     
    , May 25, 2012
    #2
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  3. pretzel

    ChrisQ Guest

    On 05/24/12 23:04, wrote:

    >
    > Replying to own post...
    >
    > Answer is, Yes. There is a 250V 10A fuse. It is neither readily visible, not easily accessible. obviously not intended to be field replaceable.
    >
    > I wonder why.
    >
    > But, can be done, if one is determined and persistent, and can get fingers in to remove a molex connector that contributes to fuse hiding.


    If the internal fuse on any switch mode psu has blown, it's usually a sign
    that either the input rectifier has shorted diodes, a reservoir cap has gone
    short, or the switcher transistors have blown. The internal fuse is usually
    rated higher than the normal line fuse and is a point of last resort,
    protection
    wise, though they do sometimes open due to switchon surge after many years.
    If the pattern of use is regular power on / off, then this may be the case.

    If you are a dab hand with soldering iron, try replacing the fuse.
    Nothing to
    lose other than the fuse and it may possibly fix the problem. Make sure you
    use an anti surge, slow blow variety, not the fast blow...

    Regards,

    Chris
     
    ChrisQ, May 26, 2012
    #3
  4. wrote:
    > On Thursday, May 24, 2012 2:43:54 PM UTC-8, pretzel wrote:
    >> We have an E3500 that is, of course, long past EOL. However, we still
    >> use it as a test box. Recently, it developed a failue of one of the
    >> Power/Cooling Modules. We were able to replace it with another PCM
    >> from a bone yard E3500 (which the current one is on its way to
    >> becoming, it would seem).
    >>
    >> The properly functioning PCMs display a solid green power indicator
    >> LED, and a non-lit amber service indicator LED. In the malfunctioning
    >> PCM, both LEDs were entirely off. The E3500 Reference Manual states
    >> that that condition (Off/Off for Power and Service LEDs) means, "No AC
    >> input".
    >>
    >> Now, when we move the defective PCM around in the various slots, it
    >> always has unlit LEDs, and the other two PCMs always have a properly
    >> lit green LED, and an unlit amber LED. In other words, there is AC
    >> available at all three of the PCM positions in the chassis. Hence,
    >> the AC must be interrupted in the module, someplace.
    >>
    >> That situation might hint at the possibility of a blown fuse. If so,
    >> we wonder if the PCM might be "brought back to life" by the mere
    >> replacement of a fuse.
    >>
    >> A brief inspection of what is visible by removing the sheet metal
    >> shrouding of the PCM does not reveal an obvious or accessible fuse.
    >>
    >> Is anyone familiar with this old hardware, and able to say whether the
    >> PCMs in the E3500 have a fuse that might be replacable?
    >>
    >> Alternatively, might anyone have an opinion on the significance of 2
    >> dark LEDs (= "No AC input"?
    >>
    >> Thank you for any comments.
    >>
    >> DG

    >
    >
    >
    >
    >
    > Replying to own post...
    >
    > Answer is, Yes. There is a 250V 10A fuse. It is neither readily visible, not easily accessible. obviously not intended to be field replaceable.
    >
    > I wonder why.


    fuses only protect switching power supplies from making smoke or starting
    a fire. If they blow their fuse, they're already destroyed. In a sense,
    the fuse isn't protecting the power supply, the fuse is protecting
    everything else from the power supply.
     
    Cydrome Leader, Jun 17, 2012
    #4
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