macbook resistor value next to DC/DC converter LDPR

Discussion in 'General Electronics Chat' started by ReneS, Feb 14, 2012.

  1. ReneS

    Thread Starter New Member

    Feb 14, 2012
    5
    0
    Hi guys.

    Im repairing a MacBook Pro A1278 with SD card slot.
    The IC on this picture is a DC/DC converter a LDPR.

    But the resistors connected to it are broken (cannot measurea a value)
    Does smoebody now or can somebody measure the value of the resistors on a macbook?

    please check the picture on which resistors i mean.

    http://www.mijnalbum.nl/Foto-S4ZFNXLQ.jpg
     
  2. colinb

    Active Member

    Jun 15, 2011
    351
    35
    Are you sure the resistors are broken? Did you remove them from the circuit to measure them? What does your meter read when you try to measure them in-circuit? If the meter reads an “open circuit”, then I agree the resistors are bad, but if it reads a short, you can't be sure due to what else may be connected to the terminals.
     
  3. ReneS

    Thread Starter New Member

    Feb 14, 2012
    5
    0
    removed them to measure them.

    And one of them measures "OL"
    It is the one closest to the edge of the board.

    output of the converter is now 1.7V
    And the feedback pin is not the required 1.25V but only 0.6xx Volts.


    But when the resistor is broken this makes sence.
    The chip may be damaged as well but i can't measure that without taking it off and put it on a testboard.
     
  4. colinb

    Active Member

    Jun 15, 2011
    351
    35
    Oh, interesting. I have a MacBook, but it's a different model, and it's my primary computer so I'm a little hesitant to remove any components from the main board...
     
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