U6 LT1940EFE issues.

Discussion in 'DM800HD Schematic drawings, Pcb images etc..' started by Johnny B., Jun 11, 2015.

  1. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Click on the image for a bigger view.
    U6-2012.jpg
     
  2. rufino1

    rufino1 New Member

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    Hello Johny,
    U6 too too hot.I can't even touch it.
    Not problem with the 12v but many problems with the 5V. After separating the R109 resisitor.No more heat.
    Perhaps, U6 with shortcut or the parts?
    Regards
     
  3. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When the R109 0 ohm resistor is removed, and you still have the 5v output from the U6, and it became not hot.
    Then it seems to me that the U6 is working fine, and more a heavy amp consumption from the 5v circuit.

    See this drawing for the 5v circuit,
     
  4. rufino1

    rufino1 New Member

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    Hi Johny,
    thanks for your answer.
    No 5v out at all from U6, only 3,5V aprox. when I remove the R109
    My questions is, if the U6 is defective and the reason is because it becomes to hot, or are the parts defective?
    Regards
     
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    If you have removed the 0 ohm resistor R109, and from the U6 side the 5v output is low, Then its most likely the u6.
    However... if there is a issue with the L1 coil, or resistors, or diode D1, or C90.. the voltage may collapse and the U6 may get hot when it needs to deliver the 5v.
     
  6. zablotsky

    zablotsky New Member

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    Hi, Johny! Can you download U6-drawing with higher resolution? If "yes", please make it. Otherwise I don't get any informations from it.
     
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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  8. rufino1

    rufino1 New Member

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    Hi johny,
    I hope you are great.
    Winter comes and DM800Hd repairing too.
    PIN7 of U7 in shortcut.C105 and C106 are out to check and shortcut is still there.
    Any idea?
    Thanks a lot.
    Rufino
     
  9. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Hi Rufino,
    I'm thinking of the U7 itself which may cause a short.
    But to be sure I would remove the R283 zero ohm resistor so that it not get a back feet voltage from the cpu to the U7.
    When removed,
    The U7 must deliver the 2.6v
    The cpu (leak) voltage side must give 2.3v
    More about it, see the U7 Topic