AU-999 Restoration & Modification

Discussion in 'Exclusively Sansui' started by leray1, Jan 12, 2019.

  1. leray1

    leray1 AK Subscriber Subscriber

    Messages:
    458
    Location:
    Houma, LA
    I checked the transistors and they are correct. Then I placed the cover to those boards on and the hum went away! Yay!

    The foam that was under that cover was crumbling. Replace? If so, with what?

    What about the click/pop/thump sound when switching inputs? Is it worth trying deoxit on that switch? Anything to worry about?
     

     

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  2. w1jim

    w1jim I can fix it but good... Subscriber

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    Scrape off the old flaking foam.
    I put some foam I had on hand to apply medium pressure to the top of the PCBs to keep them seated.
     
  3. leray1

    leray1 AK Subscriber Subscriber

    Messages:
    458
    Location:
    Houma, LA
    I just shop-vac'd the foam right off. So its only purpose is to secure seating the boards? I may have some I can use. If not, I'll get some.
     
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  4. stereofun

    stereofun Super Member

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    1,293
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    Wow, glad that solved the loud hum on the phono inputs, don't recall having that, just a faint hum when covers off. A band of weather strip might do the trick in lieu of the foam.

    If using the AUX, make sure you have cleaned the aux trim pot in the back. I avoid AUX all together and use tuner for my digital source, since it has a dedicated quality switch with no trimpot and it skips the rotary selector.
     
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  5. leray1

    leray1 AK Subscriber Subscriber

    Messages:
    458
    Location:
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    I finished my evening by giving it a deoxit bath, including the trim pots for aux and phonos. Tomorrow I will wrap up with some foam and put it in my main system. Can't wait...:D
     
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  6. smurfer77

    smurfer77 AK Subscriber Subscriber

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    proper pops when flipping switches sometimes indicates DC leaking through a signal path cap. The noise due to dirt is more just a scratchy sounds, or fingernails down a chalkboard if you go very slowly, whereas DC issues are more like a pop/thump.... I hope that makes sense.

    Nice work on the bias servo transistor. FWIW, I just opened up my AU-X111MOS last night and check what they use in that; a pair of C1845.
     
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  7. leray1

    leray1 AK Subscriber Subscriber

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    Would that be one or more of the green mylars?

    It's not a concern since stereofun pointed out the advantages of using the Tuner input. And since I only use two inputs (digital and vinyl) I will just have to flick a switch to change between the two - win/win.

    I couldn't get to it yesterday, but I plan on replacing the foam and putting it into my main system to finally give it a proper test.

    Although I still need to refinish the wood case...
     
  8. leray1

    leray1 AK Subscriber Subscriber

    Messages:
    458
    Location:
    Houma, LA
    I've been listening to it through my KEF 104/2 and all I can say is wow! Depth, detail and oh so clean. It lacked presence and ooomph (for lack of a better word) before but it's all there now with plenty to spare. I don't have time tonight but I'll be pulling out all my favorites to hear them again through this.

    Thank you all for all the help, guidance, and most of all, patience.

    20180923_163401.jpg

    20180923_163424.jpg

    20190212_180522.jpg
     
    Last edited: Feb 12, 2019
  9. stereofun

    stereofun Super Member

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    Congrats - great job and perseverance on your part.
     
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  10. Hipocrates

    Hipocrates Anti-Muppet Subscriber

    Messages:
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    Kef + Sansui = :music:.... Kudos!, Great work man.

    Regarding the green mylars, those can be improved using PP caps.
     
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  11. slimecity

    slimecity Super Member

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    Thats the same combination as me - cheers!
     
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  12. w1jim

    w1jim I can fix it but good... Subscriber

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    Weird - I also have my refurbed and modded AU-999 hooked up to KEF 104/2 speakers as well as my McIntosh XRT-20's.
    Enjoy the music.
     
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  13. AnalogueBen

    AnalogueBen Active Member

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    Location:
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    Nice work, now kick back and enjoy..
    Make sure to share your experience once you've become more familiar with her character.
     
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  14. rafe46

    rafe46 New Member

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    Sansui AU-999 sound amazing
     
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  15. leray1

    leray1 AK Subscriber Subscriber

    Messages:
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    Location:
    Houma, LA
    Still enjoying the amp but have a question...Why is the DC offset not adjusted to zero, or near zero on this amp?

    Also realized I never posted the obligatory old parts pic...

    20190214_175101.jpg
     
  16. stereofun

    stereofun Super Member

    Messages:
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    Location:
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    What is your offset ? - I remember at some point during the thread there was talk of using different transistors on the driver board, which is ok as long as they don't work in pairs - please make sure that TR801/803 ARE the same type, and preferably matched in hfe. I think you already verified that both VR801 pots are 5Kohms (you can do a quick measure on the two outer legs to confirm - I had a pot in my 777a completely out of spec in one side, preventing proper adjustment.

    Here is a great thread from Echowars on the subject.
     

     

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  17. leray1

    leray1 AK Subscriber Subscriber

    Messages:
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    Location:
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    I'm very familiar with Echowars thread and I don't have any issues adjusting offset. But I set it somewhere between 12 and 15 mV for each channel (don't remember exact measurements, I don't have my notes with me), which is what I thought was recommended. Looking at the service manual, it states 0+/-50mV. I'm not experiencing any issues, but I'm thinking I should get it as close to 0 as possible, right?
     

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