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    ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

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    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by Bob Latino on Fri Apr 10, 2009 8:15 pm

    I recently had a customer ask me about the date of manufacture of his ST-70. There is a code on the bias pots that gives you a good idea of what year your amp kit was shipped out by Dynaco. This also works for the Mark II, Mark III and Mark IV amps. Below is the text of the Email that I wrote in response to his Email.

    "Steve,

    On the ST-70 you can check the 7-digit number stamped on the bottom of the BIAS POTENTIOMETERS. The 4th and 5th digits are the year of manufacture and the 6th and 7th numbers are what week of that year. If for example the bias pot is numbered 1386217 - then these bias pots were made in the 17th week of 1962 - probably in early May of 1962. Since Dynaco used parts very quickly you can almost be assured that this amp kit was shipped to a dealer in 1962. If your bias pot has a "48 to 52" as the 6th and 7th numbers like "1386249" then it is possible that the pot was made in 1962 but the amp was shipped out 5 or 6 weeks later in 1963.

    See below a bias pot made in August of 1964 with a "1376430" code


    Bob"



    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by PeterCapo on Sat Apr 11, 2009 2:56 pm

    Good info Bob, thanks. The transformers often carry a date code, as well. The Mark II I am working on has a "57" stamped on the bottom of both transformers, and the numbers for the year on the bias pot are also "57." Kind of cool to be working on something from so long ago.

    Peter

    Clik2media

    Posts : 40
    Join date : 2009-01-18

    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by Clik2media on Mon Apr 13, 2009 7:35 pm

    Great info Bob, I was always curious about my stable of Dynaco's

    Listens2tubes

    Posts : 15
    Join date : 2009-04-08
    Location : New Jersey

    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by Listens2tubes on Thu Apr 16, 2009 8:22 pm

    What do you make of this. Both my MkIVs have the same bias pots. The amps are serial number 8014002 and 8047086 if that helps.

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by Bob Latino on Thu Apr 16, 2009 8:58 pm

    Since the "137" number starts both bias pots the "137" could refer to the part # from the manufacturer of these pots or possibly the machine they were made on ?

    My best guess is that the "9" refers to 1969 and the "52" refers to the 52nd (last week) of 1969. These amps were not made until 1960 so the "9" can't refer to 1959 and the Mark IV was out of production by 1979.

    I found another bias pot from another ST-70 in my pile of old Dynaco parts that has a 6 digit code like on your pot but this pot is stamped on the SIDE of the pot. This one reads "137808" - maybe made in the 8th week of 1968 ? If anyone has more definitive knowlege of the codes on the Dynaco bias pots let us know ?

    Bob



    Rowbo1

    Posts : 6
    Join date : 2011-01-27

    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

    Post by Rowbo1 on Fri Jan 28, 2011 3:41 am

    To cool, 64

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    Re: ST-70, Mark II, Mark III and Mark IV - to check your date of manufacture

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