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    On to the Mark III

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    wildiowa

    Posts : 126
    Join date : 2012-03-19

    On to the Mark III

    Post by wildiowa on Thu Apr 19, 2012 12:29 pm

    Pretty much finished the ST70 except for a few minor issues and moving on to an ancient Mark III that has been sitting for a long, long time. I see that where the old wafer-like rectifier was located on the ST, in the Mark III there seems to be a black cube looking component approx. 3/4" x 1/2" and about 1" tall....I apologize can not post photo right now I have to get another photo server...but one side is connected to the black/red cloth lead to the tranny, other side to a 50mfd 150 electrolytic cap and a resistor going to a terminal strip. Is this yet another style of rectifier, which is replaced by the modern diode as noted in the ST fix? If so I will get one and take this thing out. Which direction should the diode be oriented, i.e., stripes towards red/black tranny side or other way around? You guys have been a valuable resource thanks. IA

    wildiowa

    Posts : 126
    Join date : 2012-03-19

    Re: On to the Mark III

    Post by wildiowa on Thu Apr 19, 2012 12:52 pm

    Hey trying this photo link....Mark III
    http://www.flickr.com/photos/77404494@N03/6947744090/

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: On to the Mark III

    Post by stewdan on Thu Apr 19, 2012 1:57 pm

    Hi --

    The Red-Black wire from the power transformer goes to the Banded-End of a 1N4007 or UF4007 type diode. You can use 1N4005-6-7 types, I use the 4007 because I have them.

    The other parts (Resistor and Capacitor) go to the other end of the diode.

    There is a newer version of the Dynaco Mark III Assembly Manual somewhere on the web (I don't remember where I got mine from) that shows the stock dynaco parts connected to a 1N400x type diode instead of the traditional Selenium Rectifier --- try googling "Dynaco Mark III Assembly PDF" without the quotes.

    Have fun,
    Stew

    Bob Latino
    Admin

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

    Re: On to the Mark III

    Post by Bob Latino on Thu Apr 19, 2012 2:32 pm

    On the Tubes4hifi web site we have a complete Dynaco Mark III manual in pdf format at the link below.

    Complete Dynaco Mark III assembly manual

    Bob

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: On to the Mark III

    Post by stewdan on Thu Apr 19, 2012 3:32 pm

    Hi Bob ---

    The version of the manual at tubes4hifi site is not what I was referring to.

    Somewher in my "Web Travels" I downloaded a version of the manual that had Dynaco's Changes for the KT-88 tube and also showed a pictorial diagram (last page) with the Selenium Rectifier replaced by a 1N400x type diode.

    Is there anyway to send you a copy of the newer manual so that it might be posted here? I don't have the capability to post pictures or documents somewhere else.

    Please let me know,
    Stew

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: On to the Mark III

    Post by hawaii.ken on Fri Apr 20, 2012 3:44 am

    http://www.the-planet.org/dynaco/Amplifier/Mark%20III.pdf

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