Sansui AU-X11 Restoration

Discussion in 'Exclusively Sansui' started by SanthoshA, Sep 21, 2017.

  1. SanthoshA

    SanthoshA New Member

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    16
    I myself have recently sourced the Sansui AU-X11, it arrived at my home a day back, it works perfectly with no issues, i am using it with the japanese 100volt step down converter.
    Is there anything i need to check say for example the basis in order to ensure it works fine in a long run.
    I am yet to open it up and inspect the boards inside.

    Can some please help with the service manual for the AU-X11, i can only find the service manual of the AU-X1 online.

    Also what is the nominal DC bias value for the left and right channel to adjust bias, i would like to check and see if the bias is consistent and steady across both channels.

    I am also going through threads and posts that would be useful for my restoration.
    I would really appreciate if some one can help me find the service manuals for the Sansui AU-X11.

    I plan to keep this amplifier for a very very long and am looking at support to find out basics that need to be replaced in order to keep in good shape, also suggest on elements that should be inspected for before ordering for spares and replacement components.

    Thanks in advance for your time and support.

    Attached are the pics.
     

    Attached Files:

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  2. LBPete

    LBPete Rolling Along Subscriber

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    Welcome to AudioKarma. That's a very nice amp. Can you please post the serial number for the database. Click on the link in my signature block.

    - Pete
     
  3. slimecity

    slimecity Super Member

    Messages:
    1,732
    Location:
    New Zealand
    contact user here on AK smurfer77. He is also working on this amplifier.

    You will have an issue as service data for this amp appears to be virtually non-existant. I am advised that most of the circuitry is the same as the X1 - but not the power stages. You will note that the power stage of the X11 has fewer transistors than the X1 and the outputs are different types.

    The X11 was JP-only, which would contribute to a lack of service data.

    The X1 manual is readily available for free. Recommend you confirm what sections are identical/similar to the X1 and go off the X1 for these parts. And then pray to the God of Sansui for the other bits. Should be fairly straightforward if you post any problems here.

    Amen
     
  4. SanthoshA

    SanthoshA New Member

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    16
    I will get this done once I head back home .
    Thanks for the welcome !
     
  5. SanthoshA

    SanthoshA New Member

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    16
    Thanks for your inputs !
    I ran the amp for couple of hours and it plays properly.
    There’s a smell that comes after running like 30 mins after the amp starts to warm up .

    @smurfer77 pls share your inputs on the same .
    A brief overview - I have sourced the au-x11 it works perfectly with balanced left and right channels .
    I am yet to open it up for inspection.
    Right now it’s smelly after usage for like an hour or so. Wondering if this is something I need to take care of immediately .

    Is this fine or some thing I should attend to .
     
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  6. mjs1

    mjs1 AK Subscriber Subscriber

    Messages:
    348
    Location:
    Ithaca, NY
    Yes, welcome to AK. The AU X11 like the AU X1 has the black flag capacitors and so, if the AU X11 is currently working, replacing these should be your first order of business.

    Marc
     
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  7. SanthoshA

    SanthoshA New Member

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    16
    I finally opened up the top cover, and inspected couple of elements on the board.
    For now the driver boards are clean, with no signs of smoky residue, or dust on them.

    Please find pics below.

    I would also like to thank @smurfer77 for helping me on couple of questions.
    I will be adding more detail to this thread, will do a bias measurement and post current values here.
    The insides of the AU-X11 looks too good to be true though !
    Apart from the rust on copper chasis i neither see and smoky residue or leaky caps atleast from the top view.
     

    Attached Files:

    Last edited: Sep 28, 2017
  8. smurfer77

    smurfer77 AK Subscriber Subscriber

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    1,100
    Location:
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    :lurk:

    I now have 3 AU-X11 in need of repair, so I will eventually update my own thread and will continue to post details since there is no AU-X11 manual available.

    Your AU-X11 looks nice and clean. Those board attached to the heat sinks are the driver boards. This is where you likely have trouble if biasing up doesn't sort out your issues.

    Also, pull off those over covers and check the other boards; my drivers boards had no leaky caps but I did find some on the preamp and phono boards, which are hidden under those other panels. Also, remove the bottom panel and inspect the bottom of the 8 big PS caps. On one of my AU-X11 there is some electrolyte that has escaped...

    Take pics if you desolder wires to get boards out etc etc... the usual rules apply but especially important here since we don't have the service manual.
     
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  9. SanthoshA

    SanthoshA New Member

    Messages:
    16
    Thanks for the reply !
    I have read through your posts and the annotations done on the driver board are very nicely done .
    Kudos to you , it will be also be helpful for people like me with the AU-X11 restoring it .

    I will keep this thread detailed with pictures before I start desoldering . I have skipped the phono and the preamp boards for today as I wanted to concentrate on the bias alone which would give me a rough idea on the current condition , and effort required for the restore .

    Feeling a bit disappointed , checked bias on the right channel, the bias voltage kept increasing all the way above 30mv until which a relay clicks and the bias voltage drops to 25mv after clicking and stays there with minimal fluctuations .

    I then checked the left channel bias , the bias slowly climbs to around 30mv but no relays clicked this time . First thing I did was to drop both the bias values to 10.5mv. Rechecked after bias adjustments that the values are ranging from 10.5 to 11mv across both channels.

    An other observation which I noticed was that the bias climbs slowly with increments of 0.1mv for every 3 to 5 seconds , it kept increasing all the way till 30mv across both the channels.

    Attached are pics of underneath the AU-X11.
    The power caps look good with no signs of leakage.

    I also took a sneak peak inside the driver board after removing the bottom cover , the transistors are TO-3 for sure.
    But then I need to remove the driver board/heat sink assembly to re-verify if they have been replaced with replacements or if they are the original Sansui transistors itself .

    I did also note that the driver board soldering has been re done . The solder lead seems to be different rather say polished at the spots where we desolder 4 wires to pull out the driver board .

    Please accept my applogies for the bad picture names ,as I had to upload them from my mobile directly, and I could not find a way to rename them properly .
     

    Attached Files:

    Last edited: Sep 28, 2017
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  10. smurfer77

    smurfer77 AK Subscriber Subscriber

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    good stuff. keep the pics coming. they will serve you as a good reference, and for others who do not document their process as well as you. the underside shot of your amp shows a clean example. this unit looks in nice shape!
     
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  11. Ronito6

    Ronito6 Well-Known Member

    Messages:
    937
    Here is an easier to access version SanthoshA's pix
    (if I am being too presumptuous I will spike this entry.)
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  12. SanthoshA

    SanthoshA New Member

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    16
    Not a problem at all, on a side note does Mr.Amp8 replace the black flag capacitors too?
    I have seen that he retained the black flag caps on the work he has done(images with before driver side board, and after driver side board replacement), also regarding the small re-solder joints i noticed on the driver side boards, i do believe the work would have been done to replace the black flags, which is a good thing if my assumptions are right.

    The driver side boards will be inspected further over the weekends. As i changed the bias to 11mv across both channels, i would like to let it stabilize give it a run for couple of hours and the re-check everything.
     
  13. Ronito6

    Ronito6 Well-Known Member

    Messages:
    937
    Funny...now that you mention it.

    Amp8 never mentions or otherwise illustrates any concern for black flags.

    If you look at his after-restoration parts pile you will see none. Consistently
    [​IMG] .

    But look at his finished F-2775 board. He leaves them in.
    [​IMG]
     
    Last edited: Sep 29, 2017
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  14. Ronito6

    Ronito6 Well-Known Member

    Messages:
    937
    Just to make the point a bit more relevant, here is the X11 which Amp8 restored in 2015.

    You can clearly see that the Black Flag at position C-20 has been kept in place in the restoration.
    (Click on pic to enlarge.)
    [​IMG]

    Interestingly (to me at least) Amp8 used only Nichicon Fine Gold for 99% of the electrolytic capacitors he replaced in this restoration.
    The X11 from his 2015 restoration however appears to be Amp8's personal property, so I think he used mostly Fine Gold because of that fact.

    As you can see in the picture below, in an earlier restoration of an X11 for a customer, he used a mix of electrolytic capacitors to replace the old ones.
    (Click on pic to enlarge.)
    [​IMG]
     
    Last edited: Sep 30, 2017
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  15. slimecity

    slimecity Super Member

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    1,732
    Location:
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    Thats interesting about the black flags.

    Only today I went over my new-to-me X1 and did a stocktake of where all the black flags are on the 3 relevant boards.

    Many of the black flags I found were pitted on their surface like they had been subject to a lot of heat, a couple had expanded way past the size they were meant to be. Even from just looking at these caps you can tell that something isnt quite right about them.

    Its interesting how opinion can differ between people and forums. Only the other days I was reading on the AK Kenwood forum where people think that replacing the VD1212 diodes isnt warranted. There are plenty of posts on this Sansui forum where that would be considered heresy!
     
  16. Ronito6

    Ronito6 Well-Known Member

    Messages:
    937
    In some ways Amp8 is a bit conservative in his restoration approach I guess.
    If it ain't broke, too worn out, or in need of cleaning, leave it be.
    The plus side is of this approach that it's less work in the end.

    The only thing he does change pretty much militantly are the FETs.
    That man is an unmatched (tee-hee) FET substitution expert.

    And he is very liberal with his solder reflows.

    His ripping up and rerouting of entire trace networks on some circuit boards just to slot in new small signal relays that merely have a different foot order than the old relays being replaced is madness to me. But it certainly also shows that he is a true master technician.
     
    Last edited: Sep 30, 2017
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  17. SanthoshA

    SanthoshA New Member

    Messages:
    16
    Truly agree with you.
    The bias stabilizes properly at 11mv across both channels, but i think a thermal re grease will help them in long run for sure.

    I have been hunting for replacement transistors, but find it tough to source them.
    2ST2121 and 2ST5949 seems to be out of stock everywhere.
    Are these TO-3 transistors available anywhere ?

    Planning to keep them in stock, in case something goes bad, and another reason is i doubt, that the stock transistors are inside, is because of the solder work done on both driver boards. I cant make out the markings on the transistors without removing the boards, the only way to do it, will be to be desolder the preamp wires , and the common ground and protector ground the pcb.

    Not looking for TO-3P to TO-3 conversion though,worst case scenario will have to do it.
     
    Last edited: Oct 3, 2017
  18. mjs1

    mjs1 AK Subscriber Subscriber

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    348
    Location:
    Ithaca, NY
    2 pair of the output transistors are still available on that auction site from a reputable Croation AK member whom you will recognize if you check the site. He had quite a few but it seems that he has sold most off. Search on sansui x1.

    Marc
     
    Last edited: Oct 3, 2017
  19. SanthoshA

    SanthoshA New Member

    Messages:
    16
    Update: Finally managed to source some 2ST2121 .
    It was mad hunt across the globe,as i stay in India to source these transistors.
    Hopefully they are original.

    2ST2121.jpeg 2ST2121_Rear.jpeg

    I have also ordered the 2ST5949 and am waiting for them to reach me.
    After i get the output transistors sourced, i am planning to order all electrolytic caps for the restoration.

    I was keen on getting the output transistors sourced first as they are tougher to source and as per fellow seniors in the forum i am going to stick with ST Micro replacement transistors than the On Semi ones. I hope i am not wrong in my decision.
     
  20. SanthoshA

    SanthoshA New Member

    Messages:
    16
    Did a sine wave test across the speaker terminals, and the results are the following, i have a 0.5 ac volt difference between the left and right channels.
    As the preamp volume is increased the differences between the left and right channels are around 1volt.
    The right channel being lesser than the left channel always.

    In order to skip the preamp section negating it to see if the difference is caused due to the preamp section or the power amp section, i fed the 50 HZ sine to external inputs, and skipped the preamp section of the AU-X11, the volume knob is bypassed during this process and the power amp level knobs were set to full.
    The difference in voltage between both channels is still present.

    Is there an adjustment to correct this difference.?
    I have adjusted the DC Bias and DC Offset already, and they are at 11mv ( DC Bias) , and 0mv(DC Offset), i did also have a conversation with David and have adjusted accordingly but this ain't helping much.

    Could this also be due to weak output transistors,or is there something i am missing ?

    On a side note, the problem is not due to the left and right power amp level knobs in the AU-X11. there is no signs of hissing or cracking, when the knobs are turned. Also cleaned with Deoxit Faderlube.

    I also noticed sansui glue leaking all over the preamp board, just behind the front panel( but since we skip the preamp section of the AU-X11) i don't think it's the glue(or preamp section) that causes the marginal difference in AC voltage drop in the left channel.

    Powe Supply adjustmentsjpg.jpg

    The adjustments in the AU-X1 manual for power amp level adjustments, will they be of any help, i hardly doubt so, but would like to have inputs from fellow members.
    Also is the -10.5 volt and -47.5 volt same for the AU-X11 as i got these value from Sansui AU-X1 service manual.

    Pics of the Sansui Glue over the preamp section will be posted by tonight, it looks like the glue leak across the preamp section is quite common the AU-X1 and the AU-X11.

    Please let me know your inputs.
    Thanks in advance.
    @smurfer77 @Ronito6
     

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