Vu+ red led only, jtag connected, MEMC on serial only!

Discussion in 'VuPlus Duo Hardware troubles and Repair support.' started by pnung, Jan 6, 2019.

  1. pnung

    pnung New Member

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    Hi. I have another vu+ duo genuine box having red led Problem.
    At the u805 messure points where we normal have 2.5V, but at this box i messure 4.8V.
    So i replace u805, c807, c814, c850, c819, c848.
    Voltages are OK now!
    But in serial i only get MEMC.
    I write bootloader over jtag without problems.
    Please someone know what components are suplyed be u805 and may could be blown because of the overvoltage from u805?
    See attached picture for serial outout.

    Kind regards .
     

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  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The U805 is used for converting the 5v to 2.5 vdc and has two separate outputs.
    Main output is the coil, L805 and The zero resistors F812/F813 are the two outputs.
    You need to remove one of them to see which circuit gives a issue.
    I do not known at this moment the ways they go, but I think that this voltages are used for the cpu, and the network.
    Maybe I can tomorrow give more info about this two outputs when I'm in my workshop.

    Reason of a damaged U805, or wrong voltages could be a damaged coil which could be the input, or L805 output coil.
     
  3. pnung

    pnung New Member

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    Hi Friend. Do you know how i can Test if the three Infineon ram Chips are working right?
    Do the cpu Test Memory on Start up ?
    I wonder what let the box stop at MEMC outout ?
    Kind regards
    Peter
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Wen you have the jtag connection and it connect, then there is also a option to access the memory with the bbs software.
    It does not check the blocks, it only shows if it has data into the memory blocks.
    To check the memory blocks you need to have a bbs script, A long time ago I had attempt to make one, but it never was finished because no one could help me further with it.
     
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    And yes, normally the software/boot loader checks several things before it goes further with the start up.
    However, a complete death memory communication to the cpu may give this issue.
    Often caused due the cpu itself I think, or the voltages for it are not working.
    As far as I known it uses the 1.8v, but it may also use the 2.5v.
     
  6. pnung

    pnung New Member

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    Ok thank you so far, with jtag i get Memory Content displayed.
    But i found another Problem on all three Regulators (u801 / u802 / u805) i found short cut from PIN 1 gnd to PIN 2 vin.
    Hmm I will look at this. Any suggestions...
     
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Based on my measurements, ground to the Vin it should be something as 3.34KOhm, this is without the psu connected.
    If it's shorted while the psu is connected, then it could be the psu.
    If it's shorted without the psu, then it could be a damaged dc to dc ic, or due a cap as the C807/814/850.
    More about it see this drawing.

    [​IMG]
     
  8. pnung

    pnung New Member

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    Good morning. I messured a short cut on all three Regulators (u801 / u802 / u805): PIN 1 gnd to PIN 2 vin. But when i pulled out front panel cable short cut goes away. I belive my Problem has nothing to do with (u801 / u802 / u805) .
    Yesterday I replaced: u801 / u802 / u805 to be sure.
    You told me about the coil. How i can Check if all coils are working right ?
     
  9. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    If you have reasons to think that it's caused due the front panel then you could maybe find it by this drawing.
    It should then have a short cut between the 5v2 (not 5vs) and the ground.
    Best option is to test it with another front panel.

    Question howto measure a coil if it's has the correct value, therefore you need a uH measurement device to know if it has the correct value, cheap one could be for example the model lc200a, other option is to replace it.

    Model lc200a measurement device....


    Front panel drawing....
    [​IMG]