Transformer 784-139

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by wnlively, May 20, 2011.

  1. wnlively

    wnlively Member

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    I posted earler about finding a output tranfomer for my marshall 9005
    power amp. The schematic has 784-139 writen above the trany.

    I dont know alot about Marshalls , but when i search for that part number
    it seems to be used in a early jcm 800. would this be the trany im looking for ? It seems to be used alot in 50w marshalls.

    thanks
    Neal
     
  2. WaltC

    WaltC Member

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    What's stamped or written on a label on the actual transformer? That's a much more reliable indicator of exactly what transformer is needed.
     
  3. wnlively

    wnlively Member

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    the amp is at the repair shop 45 miles away .
    So i havent actually seen the transformer.
    The tech is saying he is unable to locate a replacement.
    He has had the amp 3 months and i had to call him so that made me wonder how hard he looked for one.
     
  4. LowellH

    LowellH Member

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    Any 50W Marshall OT should work fine. Hammond 1750N fits the bill and retails for around $80.
     
  5. WaltC

    WaltC Member

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  6. wnlively

    wnlively Member

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    First I would like to thank everyone for the help .

    Might be time for a new tech is 100% correct.

    Now im begining to wonder if the amp has even been looked at.
    It is clearly written on the xformer 784-139 9-89.

    And from what i can tell this is a fairly common tranny.

    thanks
    Neal
     
  7. Roe

    Roe Member

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    the 139 is a legendary drake 50w ot. marstran makes an excellent version of it
     
    Last edited: May 22, 2011
  8. ked

    ked Member

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    I'll second that. I built a clone using that transformer and it is very good. Check the Marstran website. This transformer definitely speaks Marshall.

    http://marstran.com/


    Ken
     
  9. BarryW

    BarryW Member

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    I'll third that - Marstran trannies are just awesome. That reminds me, I need one!
     
  10. Roe

    Roe Member

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    sorry meant drake - the 50watter were always drake
     

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