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Repairing a sony minidisc deck mds-s38

Discussion in 'Troubleshooting and Repair' started by ville900, Mar 31, 2013.

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  1. ville900

    ville900

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    Mar 31, 2013
    Hello,

    I am new to this forum and happy to join.
    I have a sony minidisc deck coming from Japan. It uses 100 V voltage (Japan one). I live in France so I usually use it with 220 V voltage, using a power transformer. This works fine.

    Recently, unfortunately, my son plugged it directly on the wall, so directly on 220V. As you can imagine, it is not working anymore !

    I opened it to see if there is some kind of obvious fuse that could have melted or something obvious. I could not see anything clear.

    I must add that I am not at all a specialist of electronics, and by far. Another way to say is that I know nothing here ! Just the basics from back when I was a student...

    I have taken some pictures of the inside if this can help. Here they are :

    This first one shows where the power cable plugs it into a circuit board (black cable):
    [​IMG]

    There seems to be 2 blue components under (capacitors ???) and 1 white one in the middle (???).

    Here is as see from above, the circuit board with the input (right) and output on the left or so I think:
    [​IMG]

    Close-up on the circuit board where the power cable comes in:
    1/ Right hand-side
    [​IMG]


    2/ Left hand-side
    [​IMG]


    Many thanks if you can help me here as I am kind of stuck.
    This deck is close to new apart from this problem. And I have many minidiscs which I won't be able to listen to anymore if I cannot repair it.
     
    Last edited by a moderator: Mar 31, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Nice photos, but can you give us one of the top side of the board.

    The problem is almost certainly going to be on the part of the board that has the caution hashing over it. The key candidates are a mosfet, a rectifier or a capacitor (in that order). If a fuse has blown, it's almost certainly an indication that one of these has failed.

    Bridge rectifiers and mosfets generally fail short circuit unless they've blown themselves apart. A failed capacitor in this case is likely to be physically damaged (bulging, leaking, or blown apart).
     
  3. ville900

    ville900

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    Mar 31, 2013
    Hello,

    Thanks for your answer.
    By top side, you mean he other side, the one with the components? If this is the case, I cannot access it as it is still mounted, and it is facing down to the box of the minidisc desk.

    Someone mentioned that there might be a "thermal fuse" in the power converter and that this fuse might be blown, but that I'd have to unmount and open the power converter to check this... which I don't know how to do.

    Does this sound like a possibility to you?

    Do you I have to unmount the circuit board to take pictures of the "top side" (which for me is the down side)?

    Thanks again
     
  4. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    yes the transformer is likely to have a thermal fuse in it, you can just see the corner of the transformer on the right side of the first pic

    With the power disconnected, and your multimeter in Ohms mode, check for continuity between the 2 pins of that orange connector.
    You should see continuity measuring maybe 1000 Ohms ( the resistance of the primary of the transformer)

    cheers
    Dave
     
  5. ville900

    ville900

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    Mar 31, 2013
    Hello,

    There is no continuity at all between the 2 pins of the orange connector (infinite resistance). I checked also, my ohm meter is working fine. So it looks like something is broken or melted.
     
  6. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    OK now just to confirm that its the transformer thats open circuit
    go across the 2 centre pins of the transformer primary as seen in pic 4

    thats the 2 pins that have tinned traces leading down at an angle and away to the right

    if its open circuit there, then the transformer is faulty and you would need a replacement.
    That complete raised PSU board is probably sold as a complete spare part

    Dave
     
  7. ville900

    ville900

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    Mar 31, 2013
    Hi davenn,

    thanks for your input. It is actually open circuit between the 2 pins that you mentioned.
    Do you have any clues as to where I could find the whole PSU (what does PSU stand for?) board as a replacement as I am a total newbie?

    Also, would there be a way to open the transformer and to repair it or is that beyond feasibility?

    Many thanks
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    PSU == Power Supply Unit (aka Power Supply, Power Supply board, etc)
     
  9. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    You wouold probably have to go to Sony or one of their service centres and see if they can supply/are willing to supply a replacement board if its atill available as a spare part
    Any bit of gear over 5 years old will be difficult to get spares for many of the big companies dont stock spares for "older " equip any more. They want you to buy their latest whizz-bang model ;)

    Dave

    PS. ya never know you may find one on eBay
     
  10. ville900

    ville900

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    Mar 31, 2013
    Thanks. The unit is 16 years old... so I guess it's most likely supplies will be out of stock. And I heard that minidiscs in general are discontinued or will be very soon as the technology is out-of-date.
    So ebay is my most likely track then !
    Many thanks
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    A possible alternative, if the board just supplies power, is to use an external power supply that can produce the same rails. Alternatively make a simpler board that can create the required rails from a voltage supplied from an external power supply.
     
  12. ville900

    ville900

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    Mar 31, 2013
    Thank you.
    This sounds interesting... but too complex for me I presume.
    I am close to giving up. Or I'll try to find a replacement circuit board in an old minidisc drive on ebay.
     
  13. ville900

    ville900

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    Mar 31, 2013
    Hello,
    I am reopening this topic after 4 years as I finally got the technical drawings from Sony showing the inputs and outputs of this power transformer. Would anyone be able to help me rebuild it, or to rebuild it for me, from these drawings?
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Post the information you have, and let's see! (we've all been waiting :))
     
  15. ville900

    ville900

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    Mar 31, 2013
    Here's what I have : http://dl.free.fr/b7udtzTVM

    (Note : the file is available 30 days for download, after that period just ask me)
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Hmmm, it doesn't seem to want to give it to me.
     
  17. ville900

    ville900

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    Mar 31, 2013
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