The AU-X1 is, like, so hot right now.

Discussion in 'Exclusively Sansui' started by slimecity, Sep 24, 2017.

  1. slimecity

    slimecity Super Member

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    Unboxing.

    Ooooooooooooohhhhhh, exciting!

    All fuses are intact. Will remove and check all outputs tonite, then put her on the DBT......

    Looks original, no-one has been in here since leaving the factory.

    Im still not sure if this is the early "oscillation special" version or not. Would the serial number tell me this?

    IMG_1498.jpg IMG_1499.jpg IMG_1500.jpg IMG_1501.jpg
     
  2. kevzep

    kevzep Its all about the Music Subscriber

    Nice one!!
    Its quite a mission getting the output modules out, if your going to take it apart that much, might as well just go ahead and give it the full deal while its apart....

    Is it an export model so you can change the voltage over to 230V?

    I'll look forward to seeing a bit more about this.
     
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  3. slimecity

    slimecity Super Member

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    Hi Kev - no - this unit will be a keeper - 100VAC only. Doesn't worry me so long as Im not reselling, that's all good.

    Yes it looks like the power modules are tricky to extract, hopefully no soldering required at this early exploratory stage? Ie: around the output inductors at the bottom of the modules?

    Yes, more pics to come as I go. Im just stoked its original. Plus, now I know that the super-rare outputs can be replaced with plastic types - its not like I'm in a "VFET situation" or anything, if mine are gone-burger.
     
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  4. Ronito6

    Ronito6 Well-Known Member

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    The oscillation issue happened more with the early versions of the X1 which used a phono stage motherboard (the F-2772 board) that was re-engineered by Sansui for models of the X1 made circa 1980 onward to stabilize the amp better.

    There are examples of restored X1s still happily running on those original motherboards. One such X1 was restored by a chap by the name of Martin Kuhne .
    He sussed out that the oscillation mainly originated from the F-2819 flat amp board.

    The solution is discussed and applied here http://audiokarma.org/forums/index....-output-transistor-replacements.684619/page-8
    Applied and demonstrated by Harolda.

    [​IMG]
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  5. Ronito6

    Ronito6 Well-Known Member

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    But the short answer to the serial number question is if your amp was made in 1979, then you likely have the early version of the F-2772 board.

    If the third serial number from the left is a 9, you will find a first version F-2772.
     
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  6. slimecity

    slimecity Super Member

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    Thanks Ronito, very informative. I have read all the threads on this amp too, but wasn't aware of the one you posted.....

    I will also check the SN tonite and see how we go.

    This amp was WAY bigger than I expected.......its a monster
     
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  7. kevzep

    kevzep Its all about the Music Subscriber

    You have to remove the Zobel network to get the modules out, there is some soldering, and you need a fair bit of heat to make it happen too...

    Yeah they are quite big aren't they....I like them, if I ever decide to change direction from my McIntosh I will consider one of these...
     
  8. slimecity

    slimecity Super Member

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    OK - so update.....

    The phono board has the factory stability mods done to it - the tracks have been cut and those 3 caps in that formation are in place.

    Bit of a mission removing the power modules yes. Done one, and woohoo - all the outputs test fine! They did have this weird soot on them tho - at first I thought they were just snazzily-coloured outputs... see the one on one end I have cleaned up a bit.

    Will get onto the other one tomorrow morning......

    IMG_1507.jpg IMG_1508.jpg
     
    Last edited: Sep 25, 2017
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  9. Ronito6

    Ronito6 Well-Known Member

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    I'm guessing you got a 9 as that third serial number.
     
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  10. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Mine had that too, but I cleaned it off using 'Silver Dip' (& Q Tips), which is a liquid based silver cleaner, other metal tarnish cleaners will work as far as I know.

    Congratulations on your acquisition, a lot of work but so very well worth it. :thumbsup:
     
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  11. slimecity

    slimecity Super Member

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    Cheers! Yes, thats what I hear!

    Although i am in a slightly sucky situation - just bought some KEF 104.2's and was I hanging out to hear them on this amp - BUT....of course the KEFs are 4 ohm! Argh.
     
  12. Ronito6

    Ronito6 Well-Known Member

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    The X1 can handle 4 ohms.

    From http://audio-database.com/SANSUI/amp/au-x1-e.html

    Effective output (5Hz - 20kHz, THD 0.007%)
    160W+160W (8ohms)
    220W+220W (4ohms)
    Effective output (1kHz, THD 0.003%)
    160W+160W (8ohms)
    220W+220W (4ohms)
    THD (5Hz - 20kHz)
    0.007% or less (8ohms)
    0.008% or less (4ohms)
    Cross modulation distortion (70Hz:7kHz=4:1)
    0.007% or less (8ohms)
    0.008% or less (4ohms)
     
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  13. JOMARK911

    JOMARK911 Super Member

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    Yes one of the few SANSUI's rated for 4 ohms loads. Actually they were almost all rated for 4 ohms but not with a power increase. Apart from the psu's power limitations there must have been power amp's design limitations also. Like the op transistors plethora , the heat sink dimensions , and some other things that don't come to my mind this time.
     
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  14. slimecity

    slimecity Super Member

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    OK - now I have heard this from pretty reputable sources - that's great news about the speaker loading! I thought some of the instability issues with the earlier versions of this amp meant that it could only do 8 ohms minimum. Cheers!

    Just a query with the output transistors - I have tested all of them and they tested as working however I have a bit of variation with most of them - many of them tested about 20 hFe (whatever the measurement unit is!?) differently between the base to emitter; and base to collector. In most of these cases the measurement was higher between base to emitter, than base to collector. One or two measured 30 hFe higher.

    Anything to worry about?
     
  15. kevzep

    kevzep Its all about the Music Subscriber

    Don't worry about it.....

    They are intact, they'll be fine..:thumbsup:
     
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  16. slimecity

    slimecity Super Member

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    So next steps -

    In terms of firing her up for the first time - to see if I have audio - and using a DBT on a 100VAC supply of course.....

    Can I do this for a quick test or should I instead just replace all the black flags first?

    As i'm lazy as, does anyone have a parts and location list for all these black flags and what recommended replacement cap types are? If not, no worries.....

    There are some fusibles in this amp too, which will be next to go, then all caps (assuming the amp is working fine, of course!)

    Note the site I purchased this from had pics of the amp fired up, with panel LEDs working, so I know it has been powered on (with no protection) recently.
     
  17. kevzep

    kevzep Its all about the Music Subscriber

    Replace the black flags the trimmers (All of them) and the two fusible resistors in the power amp driver boards minimum....I'll hedge a bet those fusible resistors in the driver boards have drifted.
     
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  18. Ronito6

    Ronito6 Well-Known Member

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    Speaking of resistors...On the 2775 driver boards you will likely find resistors R36 and R37 so beat up that they will crumble to bits when you touch them.
    Others have reported the same in other threads.

    No one as yet has explained why those positions on those boards are so punishing to the resistors positioned there, but I am curious to see how you address that issue.

    I ended up using 1 watt resistors .instead of 1/3 watt originally installed at positions R36 and R37. Nothing has melted down yet.

    Actually, since 1/3 watt resistors were impossible for me to source anyway. that wattage was going up regardless as 1/2 watt were the closest available alternative.

    I just kicked it up a notch ( BAM!!) above a 1/2 watt and installed those 1 watt ones I mentioned.
    [​IMG]

    (Well, no BAM actually and thank goodness.)
     
    Last edited: Sep 25, 2017
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  19. slimecity

    slimecity Super Member

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    Yea thats preferred for sure.

    Without me pulling apart this amp totally at this stage would like a bit of guidance on exactly which boards have the blag flags in the X1? So I can order replacements without having this amp strewn all over the floor of my small flat just yet?

    Im not sure what designation these caps have in the SM, are they MC (Mylar) or PC (Polystyrene)? I still havent really established what the blag flags are made out of, and if they are PC types, there are a lot of other standard polystyrenes in this amp also.

    So far I have it that there are blag flags in the power output modules (F2775).

    From the other boards I can visually see from the top or bottom, I cant see any on any of the:
    • Phono boards (4x) or F2772 mother phono board.
    • On the F2781 main power board.
    • I also cant see any on the F2773 muting circuit board.

    So - I know they are on the F2775 output boards, and that leaves the:
    • F2774 Buffer amp board,
    • The F2778 "Regurated" supply board (lols - thats what the SM says!) and
    • The F2819 Flat amp circuit board.

    Does anyone know if there are any on these above boards?

    Another question is replacement type. I know the preferred course is silver mica. If i instead go ceramic - is there any particular TYPE to use, and also what voltage?

    THANKS!
     
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Definitely some on the Flat Amp board, looks like 2 x 30pf, 2 x 10pf and 2 x 4pf (from SM) - but I found 2 on the bottom of the board (value forgotten), so, as always best to visually check yours.

    I'll check the F-2774 Buffer Amp Board...

    Update
    It doesn't look like it, but my buffer amp board was significantly different (fewer components) to the SM picture.
     
    Last edited: Sep 26, 2017

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