HIG024 Rev:D5 power failure

Discussion in 'Hardware troubles and Repair support.' started by yo3, Feb 6, 2020.

  1. yo3

    yo3 New Member

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    Hi to all!
    I have strange faulty board.
    7-
    6-
    5-16,6R
    4-59,7R
    3-506R
    2-19,5R
    1-321R
    I found Q1109 and Q1106 defective, all this above measurements was without R1100, R1131,R1112 and this Q1109 and Q1106.
    Any ideas?
    Thank you
     
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Measurement results from an incomplete motherboard are for me difficult to determine what it may be but as far as how I see it with this information I'm guessing that it has a 3.3v and 5v circuit issue thus it could be the U1101/3.3v, or maybe also the U1102/1.2v is involved with it.
     
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  3. yo3

    yo3 New Member

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    Thank you for the informations.
    What you suggest? To connect back this components and check again?
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah, I always do the measurements first before I remove some parts, this to get a good references of the measurements compared from a good motherboard.
     
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  5. yo3

    yo3 New Member

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    Hi, I connect back this and now I have:
    5-9R
    4-58,9R
    3-270K decrease to 70K, not stabile
    2-19,3R
    1-326R
     
  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Based on the good ohms measurements of the dm800se fault findings overview.
    It seems that the 5v value is fine, but the 3.3v not.
    Others as the 70K versus 45.5K of the 2.5v seems to me no issue.

    I think, a issue with the 3.3v circuit because normally it should be into the 1700 ohm range while yours is 85.9 ohm.
    But the problem with this circuit is connected/feeding with/to several parts as the U1205, memory chips and the nand flash chip etc..
    Thus it's not simple to say which may caused it.
    But, it may give an indication when you remove the inductors, L1108 (memory chips), and/or the L1109.
    when removed, see if the ohm value rises from the U1101 side or not.
    When it does, then it's most likely not the U1109, but an issue after one of the the inductors which will be harder to find and in some cases unsolvable because it's also connected to the cpu.
    More about this L1108, see this picture, more about the 3.3v circuit, see this drawing.
     
  7. yo3

    yo3 New Member

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    Thank you for the help...Now I am confuse..I don't understand what is happened!
    I take off L1108 and L1109, the value are:
    5-8.8r
    4-60,1r
    3-down to 10K
    2-19,8r
    1-320r
     
  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah others may give an other result when the two inductors are removed, but still, as far as I see it, it seems still to be the 3.3v circuit, in any case it's the lowest value.
    And assuming you have these 8.8r value, then it could be caused due the Q1106, or the U1101.
    Assuming it is the U1101, and it's caused from pin 15, then you could remove the r1115 resistor to see if the value chances, or just remove the U1101.
    In any case, since you already had removed the Q1106, and declared faulty as also without any improvements, then the most logic thought seems to be also an defective U1101.
     
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  9. yo3

    yo3 New Member

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    I take off R1115 , no change
    I have on L1104 (12V) very low resistance 18,5ohm
    I disconnect R1150 from U1103 and now I have exactly 180 ohm on pin 5
    I will order new mos-fet's and I will check again
    Thank you!
     
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