BA-5000 Rework

Discussion in 'Exclusively Sansui' started by HDJR808, May 10, 2016.

  1. JOMARK911

    JOMARK911 Super Member

    Messages:
    2,378
    Location:
    Athens Greece
    Yeah that's why i quoted your post. Isn't that funny? at least?
     
  2. HDJR808

    HDJR808 Active Member

    Messages:
    218
    Funny, yes. Looking at the operation of the meters, this is my amateur's guess about how this was set up:

    I am assuming that the raw meters are voltage meters, and that part of the purpose of the meter driver boards is to reduce the voltage level to a point to not overdrive the fine mechanisms in the meter itself. But also, looking at the 2, 4, and 8 ohm voltages of the transformer windings, they are not a linear variation into those loads, and I am guessing that the ic circuitry on the board is a means of making the meter perform in a linear fashion for the three maximum output voltages. And while the Odb and -40db levels are adjusted with the 49V and 490MV references from the outputs of the 8ohm tap, the 4ohm tap is used to drive the circuitry and the range is interpolated for the 8 and 2 ohm output voltages.

    I could be completely out to lunch on this, but as I said, that's my amateur's guess.

    Hopefully tomorrow I will get some more of the wiring harness completed...
     
  3. HDJR808

    HDJR808 Active Member

    Messages:
    218
    Today was the replacement of the line level coax cables from the buffer board to the driver boards. On the originals, the terminal housings had been removed, and then the terminals were clipped and soldered directly to the header posts. This is one of the two new leads that I made up:

    IMG_1393.JPG

    The terminal housings and terminals are new, and the coax is some high quality 26awg cable stripped from a multi-conductor RGB video cable. This coax has a 16.7pf per foot capacitance, which is good spec for line level audio interconnects, but to be certain there were no anomalies I made up some interconnects with it that I have been running between my amp and preamp for a few months now and they sound fine.

    The original harness uses a single terminal housing at the buffer board that is polarized, and the two leads split from there:

    IMG_1394.JPG

    I had no luck finding that particular terminal housing, but was able to use the same housings on the source end of the cable as are on the driver boards and just install them side by side:

    IMG_1425.JPG

    Now it's time to figure out what to do with the power switch. The original appears unmolested on the outside, but considering the condition of everything inside this amp my guess is that it's pretty sludged up internally. I'm just not sure that I want to try and crack it open...
     
    Hyperion and smurfer77 like this.
  4. super98lsc

    super98lsc AK Subscriber Subscriber

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    962
    As long as its not that old Kapton wire that shorted out and caused plane crashes due to brittle and chaffed insulation.
     
  5. HDJR808

    HDJR808 Active Member

    Messages:
    218
    I had never heard about (and kind of wish I didn't know now :yikes:) the Kapton aircraft wiring issues....

    But no, the wire I have used is Tefzel, in the Teflon family, that appears to be one of the wires of choice to supplant the Kapton wiring that has been implicated in aircraft failures. The Tefzel is supposedly a tougher sheath than Teflon, and the 22759 spec is tinned as opposed to a lot of the silver plated Teflon wiring.
     

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