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    Mk3 Output Transformer Extra Wire

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    sandy

    Posts : 36
    Join date : 2011-03-04
    Age : 54
    Location : Los Angeles, CA

    Mk3 Output Transformer Extra Wire

    Post by sandy on Sun Apr 03, 2011 5:51 pm

    Working late last night on the pair of Dynaco MK3's I noticed and extra wire coming out of one of the Output Transformers. Looked at all the rest and none had the extra White Wire. It's connected on the output side (speaker) and seems to be about 30ohms from black to this white wire.

    Was this from a different model amp or an early version? I couldn't find anything in the M3 schematic that shows this tap.

    Sandy

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Mk3 Output Transformer Extra Wire

    Post by Bob Latino on Sun Apr 03, 2011 6:33 pm

    Some Dynaco Mark III's had a 70 volt line out for use with multiple speakers like in a church or auditorium. The extra white wire is probably for an application such as this.

    Bob

    sandy

    Posts : 36
    Join date : 2011-03-04
    Age : 54
    Location : Los Angeles, CA

    Re: Mk3 Output Transformer Extra Wire

    Post by sandy on Mon Apr 04, 2011 11:06 pm

    Thanks Bob, I have a few pics of the old chassis that is came out of but I can't see where it goes. It might have been coiled up in the bell of the transformer and didn't notice it when I tore them down.

    Sandy

    DynakitParts
    Admin

    Posts : 183
    Join date : 2008-11-30

    Mark III-70

    Post by DynakitParts on Tue Apr 05, 2011 8:17 pm


    Sandy,
    I have a pair of these amps...The manual say's:

    The Dynakit Mark III-70 is identical to the Mark III with the addition of a 70 volt
    output for line distribution systems. A different transformer (A-431-70) and a five
    screw terminal output strip are the only variations.There is an additional white wire
    coming out of the output transformer. This should be connected to the fifth terminal.

    Obviously, this transformer is mounted on the more common Mark III chassis having only
    the four screw terminal. You can just terminate this lead. (tape off)

    Manual further states: The use of the (4)(Cool and (16) ohm outputs is unaffected by the
    presence of the 70 volt output. The output impedance of the 70 volt tap is 83 ohms.
    When the 70 volt output is used, there are commercially available loudspeaker matching
    transformers designed specfic for this application delivering up to 60 watts continous
    rated power.

    I should note that original chassis for this model had a wider cutout to mount the
    five screw terminal strip. The fifth screw position was screened as 70V.

    Kevin @ Dynakit

    DynakitParts
    Admin

    Posts : 183
    Join date : 2008-11-30

    Mark III-70

    Post by DynakitParts on Tue Apr 05, 2011 8:20 pm


    Don't know how that "Happy Face" got inserted in the copy...Should have been an (Cool.

    LOL....Kevin

    sandy

    Posts : 36
    Join date : 2011-03-04
    Age : 54
    Location : Los Angeles, CA

    Re: Mk3 Output Transformer Extra Wire

    Post by sandy on Tue May 03, 2011 6:51 pm

    Thanks Kevin!

    Yeah, watch out when using parenthesis Smile


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