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


    Help with Z565

    Share
    avatar
    dmtparker

    Posts : 14
    Join date : 2014-09-25
    Location : Bocas del Toro, Panama

    Help with Z565

    Post by dmtparker on Wed Nov 30, 2016 6:44 pm

    I am trying to rehab an old SCA35. The colors on the leads of all the transformers have faded to the point where no identification is possible. I worked out the power transformer by measuring resistance between the various leads and matching it to the schematic, but I am having trouble with the Z565. From the schematic, the highest resistance is between BL/W and BL. I measure that to be ~450. I had guessed that the two twisted pairs (BL/W-GR/W & BL-GR) would be the same, but they are not! One pair measures roughly double what the other does. Also, the red "center tap" is not centered, but sits at about the 40/60 point. (I actually think I remember something about the 'ultralinear tap' being @ 40%, but I don't know from which end!)
    So my question to any of you who might have a SCA35 and be willing to pull the tubes and measure the resistance between pins 7-9 of V5 and 7-9 of V6 (or V7&V8) and tell me which is higher? If my transformers are any good, one set should measure in the 160-180 range and the other 265-310, so very obviously different. A ST35 should be the same as it is the same transformer. In that case it is pins 7-9 of V2 & V3 (or V5 & V6).
    Thanks for the help!
    avatar
    Bob Latino
    Admin

    Posts : 2525
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Help with Z565

    Post by Bob Latino on Thu Dec 01, 2016 10:47 am

    Take off the two transformer bell covers. The true colors of each wire should be apparent under the covers.

    Another thing to consider > One of the most overused and incorrect internet MYTHS about the original Dynaco tube amps is that those "cloth lead output transformers" are somehow superior to modern machine wound transformers. Over the years I have measured the resistance between leads on original Dynaco (especially the OUTPUT) transformers. I have found (as you have found) that the resistance measurements from the two output transformers on original Dynaco amps can sometimes vary quite a bit from one output transformer to the other.

    Bob
    avatar
    dmtparker

    Posts : 14
    Join date : 2014-09-25
    Location : Bocas del Toro, Panama

    Re: Help with Z565

    Post by dmtparker on Thu Dec 01, 2016 12:40 pm

    Bob Latino wrote:One of the most overused and incorrect internet MYTHS about the original Dynaco tube amps is that those "cloth lead output transformers" are somehow superior to modern machine wound transformers.Bob
    It is not that I think these are necessarily 'better', it's just that I HAVE them and do not have new ones (and getting anything to Panama is not easy Cool
    So, if anyone is willing to measure the values of pins 7 & 9 of their output tube sockets and give me the results, I would still appreciate it.

    Sponsored content

    Re: Help with Z565

    Post by Sponsored content


      Current date/time is Mon Jun 26, 2017 8:16 am