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Enermax modu87+ 500W wierdness

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    Enermax modu87+ 500W wierdness

    This might be interesting to some.
    I recieved this power supply with the issue of "not starting the computer"

    The unit is a resonant topology with syncronious rectification plus two DC-DC converter on the secondary. All capacitors are NCC.
    The owner attempted to repair the psu by replacing some caps... then putting the originals back.

    When I powered up the unit for examination there was a stable 5V standby supply but after a few minutes a capacitor vented in the standby circuit. This power rail is generated by a TOP265EG monolithic device.
    I replaced the exploded capacitor and started measuring voltages. After a few minutes the new capacitor blow up.
    I started tracking the circuit and looked for more faulty parts. According to the TOP265EG datasheet the cap that blows up at C3 position is in the feedback bias for this standby circuit.




    Then I noticed something wierd.
    When powered there is 6V across this capacitor which is ok. But looking at the silkscreen the polarity is wrong! I couldn't believe it is reversed until I looked at a photo of an original unit for comparison.



    So this means that the owner reassambled the unit back according to the silkscreening... and it fooled him too.
    After installing another capacitor, this time reversed, there were no more explosions. I also replaced a fast diode just in case it might have been damaged.


    Anyway, the original problem was caused by the faulty PS231 supervisor. The power-ok signal wasn't present when the unit was turned on. Replacing the ic solved the issue. I suppose this silkscreening mistake must have been known by Eneramx back then... after several failed units during testing.
    Attached Files

    #2
    Re: Enermax modu87+ 500W wierdness

    Originally posted by pdavid View Post
    This might be interesting to some.
    I recieved this power supply with the issue of "not starting the computer"

    The unit is a resonant topology with syncronious rectification plus two DC-DC converter on the secondary. All capacitors are NCC.
    The owner attempted to repair the psu by replacing some caps... then putting the originals back.

    When I powered up the unit for examination there was a stable 5V standby supply but after a few minutes a capacitor vented in the standby circuit. This power rail is generated by a TOP265EG monolithic device.
    I replaced the exploded capacitor and started measuring voltages. After a few minutes the new capacitor blow up.
    I started tracking the circuit and looked for more faulty parts. According to the TOP265EG datasheet the cap that blows up at C3 position is in the feedback bias for this standby circuit.




    Then I noticed something wierd.
    When powered there is 6V across this capacitor which is ok. But looking at the silkscreen the polarity is wrong! I couldn't believe it is reversed until I looked at a photo of an original unit for comparison.



    So this means that the owner reassambled the unit back according to the silkscreening... and it fooled him too.
    After installing another capacitor, this time reversed, there were no more explosions. I also replaced a fast diode just in case it might have been damaged.


    Anyway, the original problem was caused by the faulty PS231 supervisor. The power-ok signal wasn't present when the unit was turned on. Replacing the ic solved the issue. I suppose this silkscreening mistake must have been known by Eneramx back then... after several failed units during testing.
    That looks like a really nice PSU too, sad to see that was an issue with it. However seems that once you know about the issue and fix it, it seems to be a very nice PSU.
    Popcorn.

    Comment


      #3
      Re: Enermax modu87+ 500W wierdness

      It's a good 500W Gold unit even if it's a bit old. This faulty supervisor problem might be rare too.

      Comment


        #4
        Re: Enermax modu87+ 500W wierdness

        ah well looks like factory qc in china is getting from bad to worse from the wrong silkscreening on the pcb. i saw another opposite issue from this in another member's topic. the silkscreening was correct but the factory installed the cap in reverse/wrong polarity.

        Comment


          #5
          Re: Enermax modu87+ 500W wierdness

          Dears

          Apologize reopening this, but I have wierd symtpoms in my Enermax Modu87+ module - after going to Sleep, CPU fan spinns @max speed but maimboard (Asus MVG) is off.

          Due to Custom HTPC setup Replacement with another model.

          Any idea if this can be fixeds

          Comment

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