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Marantz 2245/2270 P750 Amp Board Replica

Discussion in 'Marantz Audio' started by ton4eff, Nov 9, 2018.

  1. ton4eff

    ton4eff Active Member

    Messages:
    173
    Location:
    Тополовград
    3 years ago I did a Marantz 1060 P700 amp board replica, it came out pretty well, trying to preserve the original look/layout of the PCB. You can take a look at this old thread.

    I had a few requests to do the same thing with P750 amp board for 2270/45 models. Since I don't have this board yet to use as an example for measuring the exact physical dimensions (I'm using pdf files from SM for now), I'll have a few questions about it. I'm also accepting suggestions for minor modifications, if needed for easier fitting modern parts, maybe changing some hole/slot sizes, distances etc... So thanks in advance for everybody participating in this thread!

    First thing I noticed - they used too completely different layout versions of this board:

    The early one:
    P750-early version.jpg
    And revised:
    P750 - later version.jpg

    Hmm, so I have to make 2 boards instead of only one...
     

     

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  2. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,913
    Location:
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    Making both would be great. But, if the revised version started at 3901 (not sure if that can be determined or not), then there would be much more demand for that one. I'm not sure the low demand would warrant the work on the original one.
     
  3. ton4eff

    ton4eff Active Member

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    173
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    Тополовград
    I'm doing this mostly for fun as a hobby. Preventing some units from parting out because of the scorched/burnt amp board is a good thing too I think. Demand is not a priority for me. And the two boards will use the same parts library in PCB editor... We'll see. I need the exact physical dimensions of this board while I'm waiting one to arrive, so if someone have one to measure hight/width would be a great help for a start.
     
  4. ton4eff

    ton4eff Active Member

    Messages:
    173
    Location:
    Тополовград
    OK, figured out the board size - took the standard TO-66 socket (H758 and H759) distance between the holes - 24.4mm, interpolated the board in AI and resized the PDF to fully match with this transistors holes distance - the result is 150x110mm. Now it's time to vectorize some holes and slots...
    p750 size.JPG
     
    Last edited: Nov 10, 2018
    Mike Sweeney and Steven Tate like this.
  5. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

    Messages:
    420
    Location:
    Orange CA
    15cm x 11cm new design

    ref 1 center mount hole for L751 left to right 2cm x 5.5cm
    ref 2 H759 top mount 5.5cm 3.56cm bottom 5.5cm x 1cm
    ref 3 C751 14cm x 5.2cm 14cm x 1.2cm
     
  6. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

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    I've got scans of top and bottom too..
     

     

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  7. ton4eff

    ton4eff Active Member

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    Thanks for the measurements Mike, as expected, there are some discrepancies, they will be corrected if you send me that real board for reference. :)
     
  8. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

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    Discrepancies? no, tell me it's not so ;) Not to worry, the board will go out into mail on Monday.
     
  9. quadtech

    quadtech Active Member

    Messages:
    487
    Hi Mike, could you post the scans here for future reference?
     
  10. ton4eff

    ton4eff Active Member

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    Just finished "drilling" the pad holes and slots above the PDF files. :p They are only 430 if wondering... You can count them if you don't believe me. ;)

    old_drill.JPG new_drill.JPG
     
    Last edited: Nov 13, 2018 at 3:56 PM
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  11. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

    Messages:
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  12. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

    Messages:
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    Location:
    Orange CA
  13. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

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    Location:
    Orange CA
    OEM Parts load out.
    IMG_6903.jpg
     
  14. ton4eff

    ton4eff Active Member

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    Тополовград
    Oh, this is an earlier P750 version, that's why the huge discrepancies with your references, Mike. I checked against newer revised version. Now, comparing against the older version PDF, it looks much better.
     
    Mike Sweeney likes this.
  15. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

    Messages:
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    For replacing C751.. here are some sizing differences. The smaller is a Nichicon and the bigger is a Panasonic. The Panasonic is a near perfect match for the wide holes.
    IMG_7045.jpg
     
  16. ton4eff

    ton4eff Active Member

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    I'll make the pad hole diameter for this one 1.2mm just in case. Most of the smaller caps and resistors I left with 1mm. Making the distance between the pads shorter is possible, but I'll live it as it is. Somebody may wish to put 630V cap instead 250V. The chances to fit one will be greater.
     

     

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  17. tranguru

    tranguru Active Member

    Messages:
    201
    Location:
    Brussels
    Nice work!

    what would happen if you made it double sided, where the other side would only be the ground (in addition to the ground circuits in the regular side ? )
    This a low frequency circuit so maybe it will no effect at all.
     
  18. ton4eff

    ton4eff Active Member

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    The best effect could be a ground loop problem. ;)
     
  19. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

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    Location:
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    I was thinking you could extend the trace for this cap with double holes. Since it's on the edge and nothing traverse the cap ------O----O O---O------
     
  20. ton4eff

    ton4eff Active Member

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    173
    Location:
    Тополовград
    I'll think about this cap when I get there... The holes are already in the PCB editor and a little progress with the silkscreen layer today:
    silksreen.JPG
     
    Last edited: Nov 13, 2018 at 3:59 PM
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