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    Presentation and my ST70

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    Pillo69

    Posts : 104
    Join date : 2012-04-11
    Location : Granada (España)

    Presentation and my ST70

    Post by Pillo69 on Sat Apr 14, 2012 4:17 pm

    Hey.
    I stand on this forum and get some pictures of my newly acquired ST70.
    My name is Pepe and I live in Spain. I have some questions to the email from Bob he has kindly answered. And after reading the interesting articles from this forum I decided to register.
    Please forgive my poor English, please excuse any doubt because of this misunderstanding.
    I would like to inform me about the model or age of my ST70 I have not seen any pictures with the same front, also has three screws on the sides.
    The rectifier tube is bringing Art274B I changed to a 5AR4C RUBI, the 7199 are the USA, and the outlet valves are 3 brings Sovtec EL34 valves and 1 valve believe GE 6CA7.
    The PCB tracks was loose and very weak and I took when I bought the Orange Drop capacitors for manufacturing me an equal and replace all components.
    Waiting for your comments














    Bob Latino
    Admin

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

    Re: Presentation and my ST70

    Post by Bob Latino on Sun Apr 15, 2012 10:10 am

    Hi Pepe,

    Your English is fine ...

    Your Dynaco ST-70 was made in the mid 1970's. It is one of the later ST-70's because it says "Blackwood, NJ" on the front face. Dynaco didn't move to Blackwood, NJ until about 1973. You also have one of the newer fiberglass driver boards which came out in the '70's. The first (earlier models) of the ST-70 date back to 1959. Your amp was built from a kit and not factory wired. Factory wired units have rivets to hold on most of the components (except the two switches), while kit built units used 4-40 pan head screws to hold the components to the chassis.

    Bob

    Pillo69

    Posts : 104
    Join date : 2012-04-11
    Location : Granada (España)

    Re: Presentation and my ST70

    Post by Pillo69 on Sun Apr 15, 2012 3:35 pm

    Bob, thanks for your attention.

    After writing the previous article, I read a forum post where you explained how to know the age of the amplifier due to the numbering of the bias potentiometers. And indeed, belongs to the year 1976.
    My fear was that he was a model ST70-II.

    In another area of ​​the forum questions ask about some doubts on the amp.
    A greeting.

    Pepe.

    Pillo69

    Posts : 104
    Join date : 2012-04-11
    Location : Granada (España)

    Re: Presentation and my ST70

    Post by Pillo69 on Wed Nov 28, 2012 12:36 pm

    Updated this thread to include the PAS preamp I bought a few dates through Ebay. I've changed the front plate, I replaced the selenium rectifier diodes 1N4007 two, 2200 uF capacitors and capacitor filter. RCA jacks have also been replaced. Likewise I modified the PCB PC5 and PC6, as explained in the forum, for update. In a near future I would like to replace the knobs and selector. The rectifier tube is again a high emissivity, but the four 12AX7 tubes have been replaced by a new electro-Harmonix.

    On the ST70, I made a few tweaks to the power supply, rewound the transformer at 230 volts (European strain) and took the opportunity to expand in the secondary amperage before this change had some problems with the Bias and tube rectifier. The filter capacitor so I substituted for Authentic Cap (80-40-30-20 of 550v.) As recommended by the friend Bob, I finally replaced the power tubes that brought (each other) by a quartet Electro-Harmonix 6CA7.

    Now I'm enjoying every day of my computer without any problems, and I hope for many years.





    Soundpreserver

    Posts : 1
    Join date : 2013-03-09

    Re: Presentation and my ST70

    Post by Soundpreserver on Sat Mar 09, 2013 6:53 pm

    Hi Pepe & Bob. I recently picked up two ST-70's made at the Blackwood plant. Both appear to be kits per Bob's comment about screws vs. rivets.
    Soundpreserver

    Bob Latino
    Admin

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

    Re: Presentation and my ST70

    Post by Bob Latino on Sat Mar 09, 2013 7:08 pm

    Hi,

    The differences between the ST-70 factory wired and the kit built amp are outlined at the link below.

    Differences > factory wired and kit built ST-70's

    Bob

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