No 2.5V

Discussion in 'Hardware troubles and Repair support.' started by Jane, Nov 4, 2016.

  1. Jane

    Jane Member

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    Hi Johnny,

    I have a power supply that supplies all voltages in a correct way , if NOT connected to a mainboard.
    That means
    14V
    GND
    6V
    3.3
    12
    12
    GND
    5
    GND
    3.3
    GND
    2.5
    2.5
    GND
    If connected, there is only 0.5V instead of 2.5V. Sometimes from the beginning there is correct 2.5V but after a while it drops to about 0.5V. I can hear a quite noise from somewhere in the power supply.
    Then the voltages are
    14
    GND
    6
    3.3
    12
    12
    GND
    5
    GND
    3.3
    GND
    0.5
    0.5
    GND

    I replaced C404, but still the same. I think the voltage is coming from IC 400.
    When measured without any load, IC400 provides correct Vout of about 10V
    Do you have any idea what to check now? Thank you
     
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Q400, goes to the L401, and then to the 2.5v pins.
     
  3. Jane

    Jane Member

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    Johnny,
    Thank you for your reply. I replaced Q400 but the result is more or less the same.Still no 2.5V. Now I can hear noise even more( like switching) and voltages Vcc and also Vout of IC 400 drops to about 3V.
    I think first I should check why Vcc of IC400 drops so much.
    Do you know where is Vcc of IC400 coming from?
    Thanks
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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  5. Jane

    Jane Member

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    Johnny,
    Thank you for your help.Yes,replacing C109 helped.
     
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  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah this cap may produce a hissing sound with the circuit if it's become older.
    But uh.. did it also solve your 2.5v issue?
     
  7. Jane

    Jane Member

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    Yes, 2.5V was solved.Thank YOU. I replaced C109, the power supplied started OK, but after few moments it stopped completely. Then I replaced the IC101 and now it seems to work.
    Johnny, do you know where is going Vcc of IC400 comming from?
    Is it comming directly from secondary of transformer?
    And can you please let me know what kind of IC500 is ?(It is below AL heatsink)
     
  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Assuming you talk about the 5L0565 psu then are both equal (IC400/IC500).
    More about it, see this IC400-IC500 5L0565 psu pdf datasheet
    As for the source of the IC400-IC500 vdc input it's not clear for me yet.
    I've tried to follow it, but i'm a bit of lost with following the tracks.
    Maybe tomorrow, or else Friday I may be able to give a accurate drawing because then I'm be able to measure the tracks.
    As for now I needed to do it from the photo's I had made, which you are be able to see some info.
    However there may some faults made on it, as the IC500 input track.

    Click on the image for a bigger view.
    IC400-IC500-5L0565-in-output.jpg
     
  9. Jane

    Jane Member

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    Johnny,
    Thank you for your reply.
    I have only ETXEZ654M7F version. I think that the main design is more or less the same.But do you think that IC400=IC500?
     
  10. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The 5L0565 psu use the FP5001 for the IC400-IC500
    And the ETXEZ654M7F psu use the TL5001 for the IC400-IC500
    Both have the same pin description and function so yes IC400 is also the IC500.
    But both have another circuit to protect, as for the IC500, the 5v circuit and the IC400 the 2.5v circuit.

    Because you have a issue with the 2.5v, it could be due the IC400.
    I do not think of the voltage delivery to the (pin 2), or due the output (pin 1), but maybe thinking of the FB pin 4 resistors or else the IC400 itself.
    If more voltages drops, and assuming that the input voltage drops, then it could be a dual diode transistor issue.
    But this, you could measure.
     
  11. Jane

    Jane Member

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    I think the problem was caused by a primary side, IC101 and its capacitor C109. Thanks again for help
     
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  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Ah okay, at least it's solved.
    Great job, and well done.
    thumpupb.jpg