mystery output transformer

Discussion in 'Fisher' started by merdy, Nov 5, 2017.

  1. merdy

    merdy New Member

    Messages:
    7
    Hello fisher heads ,maybe someone can help or point me in the right direction
    A while back while I was on a mission to buy as many opt as possible for amp building and geetars mods ,i brought this from a family whose dad was a big engineer at ibm labs,apparently he was very close with Avery fisher as well as herb kreoes,d hafler etc
    The transformer has the marking of t 588 115 089 ,I know that's not a fisher number it's ratio is 19:1 from a similar enquirer from the web
    It's burgundy similar to their 200 amp or maybe even the 70 ,its big and heavy and I have been hunting for one for over 15 years but no luck
    One of the pics shows it next to a arcosound 330
    About 10 years ago I saw a similar one on les Paul rig as I was restoring his speakers (altec)
    I asked him and he did not remember but said he brought it in an surplus store near Kingston newyork ,he said he frequented many yard sales and junk stores that were suppliers to ibm
    Any help appreciated
     

    Attached Files:

  2. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    932
    It's the right color for a late 50's Fisher OPT.
     
  3. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    8,942
    Location:
    Ball Ground, GA
    Merdy -- Welcome to the AK Fisher Forum. If I may, the information you have received is quite in error. From my own notes of various pieces of early Fisher equipment I have serviced, I can offer you the following:

    1. Part number T 588-115 089 is in fact a Fisher part number, and was installed on their model 55-A, which was offered with 6550 output tubes.

    2. The full secondary turns ratio of this transformer is actually a measured 14.225:1, offering a reflected primary impedance of 3238Ω. The turns ratio you cited from the web could not possibly allow the amplifier to develop its full rated power output level. If you are not familiar with the early Fisher power amplifier design model, these are quite unique designs beginning with the 50A, and operate the output stage in triode Class AB2 mode, allowing (in this case) the 55A to develop 50 watts RMS.

    3. The full secondary impedance is 16Ω, tapped at 8Ω.

    4. The terminal designation is as follows:

    1 = Plate #1
    2 = B+
    3 = Plate #2

    4 = 16Ω
    5 = 8Ω
    6 = Com

    Each section of the primary winding should measure ~ 43Ω DCR.

    I hope this helps!

    Dave
     
    Last edited: Nov 5, 2017
  4. merdy

    merdy New Member

    Messages:
    7
    Omg Dave ,I am laughing and crying at the same time and jumping up and down and running around.
    My 15 year wandering is over in posting just my 4th thread
    I cannot thank you enough
    P.s are you the guy that makes the st 35 mod?
     
  5. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    8,942
    Location:
    Ball Ground, GA
    Glad the information helped!

    In typical guitar land duty, it would be well suited for a pair of EL34s configured for 50 watt pentode operation, assuming you can work with the secondary impedance taps offered.

    There are so many Dynaco modifications out there that it is hard to know which modification you might be referring to. My contribution was the development of Enhanced Fixed Bias, or EFB(tm) for short, which I first introduced on the Dynaco SCA-35, followed by the ST-35. It allows these amplifiers to operate the output tubes cooler, last longer, develop more power output, and with less distortion.

    Dave
     

Share This Page