Sansui AU-555A Rebuild Cap Coupled Goodness

Discussion in 'Exclusively Sansui' started by patfont, Mar 19, 2015.

  1. patfont

    patfont AK Subscriber Subscriber

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    The last Sansui I had here was a 9090DB and it had the diabolical dolby board problems. This 555A has the alien invasion on the Amp Board. I would like to give this a good rebuild/update and see how the Sansui cap coupled design holds up to the Marantz and Pioneer units I have worked on.

    Just want to put up some pics for starters do some cleaning and get some parts ordered.

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  2. skippy124

    skippy124 AK Subscriber Subscriber

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    Hi

    The 555A is a great example of cap coupled goodness. You probably already know, but get rid of those 2SC871's, and the XA-495G's as well

    Looking forward to seeing photos and commentary of the restoration

    Cheers

    John
     
  3. patfont

    patfont AK Subscriber Subscriber

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    Thanks John!

    Yes, here is what I have planned for the transistor part of the rebuild.

    XA495=ZTX795A
    8002=ZTX694B
    9002=ZTX795A
    2SC871=KSC1845

    also would like to replace the 2 diodes and 3 large resistors at the power caps.
     
  4. super98lsc

    super98lsc AK Subscriber Subscriber

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    Careful with the 2SC871 swaps the KSC1845-FTA ends up with a lower gain in pre-amp leading to really bright sound and lacking bass. On my 2000x I ended up pulling them and re-installing the 2SC871s and it sounds awesome again.

    Larryderouin and I did some research and found the KSC1815 to be a closer match for the 2SC871. I have 100 new ones in the bin waiting to test them out in the 2000x, I plan to do just one channel and do a comparison using a mono signal and also check the output levels on the scope to confirm my findings.

    -Rob
     
  5. stereofun

    stereofun AK Subscriber Subscriber

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    + 1 - the 1845's I used in a 505 resto averaged a 15% reduction in gain compared to the 871.

    I did keep the 1845 though and the amp sounds very very nice. No strain or lack of bass whatsoever, so that part of the equation may be case by case.

    @ Rob, do you know where to get the 1815 with suffix L - looks like digikey only carries Yta version with a gain range much lower than the 1845 ?

    @patfront, not sure if this has been suggested before - but the 555/505/777's really benefits from a larger supply and coupling caps. for the 555/505 I have used 4700's
     
    Last edited: Mar 20, 2015
  6. Alienz

    Alienz Super Member

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    Indeed, I used a Mundorf M-lytic 4700uf in the PS and recently replaced the stock coupling caps with 4700uf Nichicon KG's, sounding awesome now! :music:
     
  7. patfont

    patfont AK Subscriber Subscriber

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    Thanks for chiming in guys!

    I will proceed with caution on the 1845's, I have a bunch here that I match because I use them to replace the 2SC458's on the Marantz Phono boards.

    And yes the power caps will be bumped a bit, the couplers will be same as stock 1500uf.

    Rob I am very interested in what you and Larry are working on, let me know how the KSC1815's work out test wise.:D
     
  8. patfont

    patfont AK Subscriber Subscriber

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    I have used the Mundorf M-Lytics myself and like them a lot, the KG's are my go to. However depending on your goals the Nichicon KS are actually by a small margin more transparent then the KG's, however I feel the KG's have a little more drive and punch, again depends on your goals.





     
  9. patfont

    patfont AK Subscriber Subscriber

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    Got some tunes going tonight and running this little amp hard! Before a rebuild I like to make sure all is well, bias and center voltage are good. So now just waiting for parts to get here.
     
  10. skippy124

    skippy124 AK Subscriber Subscriber

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    Hi,

    I have had good success using BC550C in place of the 2SC871F, and 2SC2240GR for the 2SC871E and plain 2SC871

    For the XA-495 I have used 2SA970GR, and for the CDC8002/CDC9002 I have used BC639/BC604 also worth good success

    Out of interest I have checked a few of the pulls from previous Sansui amps for gain

    XA-495 - 170, 180, 150

    2SC871 - 248, 318

    2SC871E - 341, 360

    2SC971F - 451, 496, 505, 646, 680, 721, 900

    CDC8000-1 - 71, 72, 82, 84, 86, 117, 124

    CDC9000-1 - 12, 33, 33, 55

    I know there are the 8002/9002 in the 555A, but I thought that this might be of interest.

    Cheers

    John
     
  11. patfont

    patfont AK Subscriber Subscriber

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    Got a chance to get a little bit of work done on the 555 last night. Replaced the clamped caps along with 3 resistors and 2 diodes.

    The 555 sounds very nice!


    Here are some pics:

    Old Stuff

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    Top side look

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    Bottom

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  12. gslikker

    gslikker Super Member

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    real nice, having the caps original diameter size.
     
  13. patfont

    patfont AK Subscriber Subscriber

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    Removed all e-caps on the amp board. Installed the Nichicon KG couplers first.

    All large caps are in now:

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    With this wide lead spacing, I doubled up a piece of 20 gauge buss bar wire twisted and flattened it and soldered to cap lead and pad:

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  14. VintagePlus

    VintagePlus Mcintosh and B&W Subscriber

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    Beautiful work as always Pat.
     
  15. stereofun

    stereofun AK Subscriber Subscriber

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    Thumbs up !
     
  16. Rustyman

    Rustyman New Member

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    Are You measured this big elna's? All loss capacitance? I dont think so.
     
  17. patfont

    patfont AK Subscriber Subscriber

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    I can measure them if you want, just let me know. At some point and pushing 40 years it is a good idea to replace these. I want this to last another 40 years.



     
  18. patfont

    patfont AK Subscriber Subscriber

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    The amp board is now done!

    13 e-caps
    2 ceramic caps
    8 UFO's

    Boy I really hated to take them UFO's off they look so cool and actually look well made with gold plated leads.:scratch2: Someone fill me in and tell me how failure prone they really are?

    I want to give a shout out to Leestereo for somethings he helped me with. Used his rec. on the P/S diodes. Ben was also the first that I have seen to use the C0G ceramics in the signal path. I have used them in Marantz along with Jensen 4 pole capacitors and got high end to die for.

    C801/C802 are in the signal path so C0G's are in!

    The C0G's give the high end a relaxed smooth and delicate sound. YMMV!


    Here are some pics:


    The old

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    Last edited: Mar 25, 2015
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  19. petehall347

    petehall347 the brandy coffee man Subscriber

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    i cant remember a single ufo transistor dying . i also think they look cool and look well made too . think i have some new ones knocking around some-place .
     
  20. restorer-john

    restorer-john Super Member

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    The 'UFOs' are certainly not failure prone at all. They are a ceramic base, gold plated leads and a baked glass/epoxy top depending on who made them. They are Mil Spec and will outlast pretty much everything else in the amp.

    Personally, I would curve trace them, test them for noise and leave them be. Wholesale changeouts are pointless but don't get me started on that.

    What have you gained? Did you benchmark the amp before and after?
     

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