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Minit_ITX 2.5V supply is bad, design issue ?, 10.5V at power, but 2.5V at main

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It appears that the mini-itx board I have has a 2.5 volt power supply issue. 

Are the power supply modules programmed over jtag while on the board ??

The reason I ask is I have a power supply module on my now take appart mini-itx main board that has the green 2.5V light on and 2.5V at the main board power 2.5V test point, yet back at the Maxim power supply module board the 2.5V output is sitting at 10.4V.  Yes 10.4V. This is working that is the 2.5V leds is on. I see .06 ohm of contact resistance on 2.5V power module to main board 2.5V contacts with it like this if measure with power off.
  The power module connector to main board contacts do not appear tight against each other, that is looks like too high of standoffs are being used. The Maixim Power supply is also to high, thick, to have the 2.5M screws make good muti turn contact with standoffs also.   
Now, If I push the down on edge of the power module where the 2.5V is, that does not have any standoff on that edge. Guess what no 2.5V it shuts down. But I can now meaure 0 ohm between the 2.5V power pin on the power module to the 2.5V power pin on main baord. 
   So it does appear that the Maxim power supply module was put on the mini-itx board and power supplies programmed with the 2.5V contact not good, at .06 ohm; that the only way I can explain how it could have 10.2V at power board module 2.5V location but 2.5V at the test and feedback point on the main board. 

   Is there a Avnet Mini-ITX design person who I can contact in regards to failure of 2.5V supply and the design of Mini-ITX

Thanks
James Y.

Suggest,
    Fix the desgin so all four edges of the power supply are held down with a standoff and screw.  Don't care how it done it should be fixed so the power supply has four mounting points. It is a bad desgin as it is done now. Make sure to use longer screws due to Maxim power board thickness,there should be at least three or four screw turns.Did someone not have the proper height standoff so boards make full contact at connector...?

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    Just to follow up some on my first comments,
    The power supply module to main board standoffs measure .475" on what I was sent; where as I see the specs per Maxim and ADI power module data spec sheets call out only .45" board to board spacing.
      That would say the Mini-ITX is shipping with standoffs for power supply to main board that are
    .25" greater then specs.
    Hence the 2.5V or other supplies may not be making good contact if any. 
    Please correct me if I am wrong in regards to what the standoff length.

    I see by the power supply schematics I found that these are not programmed, so not sure what I have going on with the 2.5V supply when I do have good board to board contact but it fails to come up.

    James Y.


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    Hi James,

    Thank you for bringing the standoff height to my attention.  I will review what is supposed to be shipping with the board vs what is required.  if you remove the standoffs, and mate the connectors as tightly as you can (be careful with the remote sense header as it is easily misaligned), in this condition you say the 2.5V supply does not power up?  If that is the case, something may have been damaged with the supply running the output at 10V as you previously witnessed.  That definitely exceeds the output capacitor rating at the very least.  It sounds like we need to replace that power module.  Do the other supplies come up properly?  Please contact your local branch about the RMA processing.
    Thanks
    Chris

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    Hi Chris,
    Yes, I did take out the standoffs and pushed the power supply and main board together so there was no gap between the power connectors, being careful that the supply feedback return connector was aligned correctly.  This results in all the supplies coming up except for the 2.5V supply. I see the 2.5V supply LED blink on, very quick,  as I turn on the main PC supply.  So the 2.5V shuts down as it is powering on.
     
      I pulled the Maxim power module schematics and do see that the 2.5V 100uf output filter caps are rated at 6.3V, so that have been over stressed since I measured ~10.2 volts there. 
      
      I am hopefull that it did not damge anything on the Main board since it only measured at 2.5V in the case where the connection was ~.06 ohm to main board and the 2.5V supply did come up, somewhat unregulated around ~2.5V.  
       The standoffs do appear to be .025" to high. Along with the 2.5V board edge of the supply not having any standoff at all, seems to allow for the "bad" 2.5V supply connection in the first place.

    Thanks,
    James Y.    
     

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    Hey James,

    Thanks for checking.  Please go ahead and start an RMA on the power module board so we can get you a replacement.
    Thanks
    Chris