The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Beginner attempting restoration of Mark III

    Share

    j beede

    Posts : 317
    Join date : 2011-02-07
    Location : California

    Beginner attempting restoration of Mark III

    Post by j beede on Mon Feb 07, 2011 3:03 pm

    I just discovered this forum and I am glad to be here. FYI: The last piece of Dynaco equipment I owned was a ST-70 that I paid $15 for. After dusting it and rebiasing its EL34s I used it to drive a pair of Quad 57s for several years. That was (obviously) a while back. More recently I picked up a pair of Mark IIIs that were rescued from the attic of an old Victorian... and I am considering trying to get them going again. The amps are complete, but are very dirty. The 6an8 boards are so badly coated with grime that the resistor color bands are not visible. What do you recommend for safely cleaning 40 year old Dynaco PCBs of grime and flux? I see lots of flux that undoubtedly dates back to the original assembly.
    ...j

    Bob Latino
    Admin

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

    Re: Beginner attempting restoration of Mark III

    Post by Bob Latino on Mon Feb 07, 2011 4:18 pm

    Hi J,

    And welcome to the Forum. I have sucessfully used both Windex and isopropyl alcohol with a toothbrush to clean driver boards. Follow with an alcohol rinse and a clean toothbrush and much of the grime will come off.

    Another thought ... Since those original driver boards could be 50+ years old, you could just replace the driver board with a pair of VTA driver boards which will give you a better driver circuit than the stock 6AN8 circuit and a better bias system. The boards are not hard to replace ...

    Bob

    j beede

    Posts : 317
    Join date : 2011-02-07
    Location : California

    Re: Beginner attempting restoration of Mark III

    Post by j beede on Mon Feb 07, 2011 5:02 pm

    I will give Windex and isopropyl a try... I'd like to get the old flux off too. I have begun pulling the amps apart and they are not too pretty inside. Mismatched tubes, ugly solid wiring with melted insulation at the solder joints, and it looks like the chokes have been hot--wax/goo transferred onto the bottom cover. Is there a way to evaluate the power and output transformers using basic test gear? I wouldn't want to invest any more into these amps until I know if the rarer bits are any good. FYI: One amp powered up and runs okay. The second powered up and ran with a sort of "clipping" distortion--until the fuse blew after 2-3 minutes. I measured the quad cap on that one and bypassed the two bad sections, that amp is running on the bench now too thanks to your "sticky" guidelines on this forum. Thanks for that.
    ...j

    Sponsored content

    Re: Beginner attempting restoration of Mark III

    Post by Sponsored content Today at 9:27 am


      Current date/time is Fri Sep 30, 2016 9:27 am