Sansui AU-555A Rebuild Cap Coupled Goodness

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

  1. Pilsern

    Pilsern New Member

    Messages:
    45
    What a great inspirational thread! I am now recapping my second 555a -
    Does anyone know if it is possible to replace the 10D1 diodes in the AU555a with some "better" types - switching soft recovery type ?

    Thanks in advance,
     
  2. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    If you are going to replace them use 1N5392 - this is the direct replacement, and is what I would use.

    I am not recommending it, but if you want to try an ultrafast recovery type here is one:-
    http://www.mouser.co.uk/ProductDetail/ON-Semiconductor/MUR120RLG/?qs=sGAEpiMZZMtbRapU8LlZD9Yt6EMzPspS2typOwY7%2b%2bs=
     
    Last edited: Sep 15, 2016
  3. jimithng23

    jimithng23 AK Subscriber Subscriber

    Messages:
    67
    Location:
    Davenport, USA
    I'm interested in having my 555a recapped/restored as it sounds to me like the right channel is a bit weaker than the left.

    I don't have the skillset to do this on my own.... anyone in this thread point me in the right direction?

    Thanks!
     
  4. Pilsern

    Pilsern New Member

    Messages:
    45
    Thanks for your reply!
    I am asking because I just read about changing the diodes in this thread
    http://audiokarma.org/forums/index....ild-wolf-in-sheep-clothing-in-5-steps.652491/
    and "patfont" speaks highly of it.
    In the case of the 505 it is a common cathode diode - But would a regular independent diode from the same series be suitable for the 555a ?


    Thanks in advance,
     
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    When you mention 'common cathode' diodes - that suggests 2 diodes in a (3 legged) package, this means that a pair of correctly orientated/connected single diodes will do the trick.
     
  6. Pilsern

    Pilsern New Member

    Messages:
    45
    Exactly,
    then these to diode arrangement looks the same to me except for the different diode types:


    Sansui AU555A

    [​IMG]

    Sansui AU505

    [​IMG]

    regards
     
  7. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    The AU-555a diodes are singles, and the AU-505 'diode' appears to be a similarly rated dual type (common cathode).
     
  8. Pilsern

    Pilsern New Member

    Messages:
    45
    Yes, - and they are interchangeable ?
    (connected correctly of course)
     
  9. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    Well obviously you can use singles to replace a dual - but not the other way round as provision on the PCB will be different.

    Just make sure the ratings of the ones you are replacing are matched or superseded by the substitutes.
     
  10. don philipe

    don philipe AK Subscriber Subscriber

    Messages:
    1,085
    Location:
    West plains mo
    Jimithing23 I had mine restored by AK member Blaine "Blahgstrom" very reasonable and quick turnaround,He does fine work.
     
    Hyperion likes this.
  11. Pilsern

    Pilsern New Member

    Messages:
    45
    The diodes on the 555 on the left

    [​IMG]

    borrowed picture,
     
  12. adelo

    adelo New Member

    Messages:
    16
    Location:
    Greece
  13. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    Last edited: Sep 17, 2016
  14. smurfer77

    smurfer77 AK Subscriber Subscriber

    Messages:
    1,105
    Location:
    San Francisco
    Nice recap! Enjoyed the discussion of various cap types etc. still amazes me how great these machines are. Right now am listening to the Stranger Things soundtrack and doing a blind A/B/C of a ST-70(with Marantz SC-6 pre)/rebuilt-AU-777A/stock-AU-505 comparison. The 777A is king, but the 505 is pretty magical too. Might have to bring the rebuilt 555A or 505 back into rotation!

    On the UFO transistors, I replace them all and have stopped testing them. Aside from complete failure or very noisy and obvious issues, transistors also start to fail or have failure modes which are not total failure, but just get noisy and it is not that obvious at first. Having multiple stock units of the same model made for some interesting comparisons with no input and the volume up comparing the hiss. I've made started collecting noise floor recordings of various amps before and after replacing various components; the UFO (and other transistors) can sometimes be a bit noisy and it's not obvious that it has a problem. Maybe I will do a thread on all of that and rat out the most common culprits and key component locations when I have time to plot noise analysis of the samples. It's also interesting to make recordings or analysis the noise whilst removing various parts of the EM protection in the various amps. Yes, you do need the metal cover over the tone boards in the AU-777 even though it's pretty far from the power supply....(a pity since my AU-777A with transparent lid looks cooler if the preamp cover is removed)

    A properly recapped 555A is audio nirvana to my ears. Again, congrats on the beautiful rebuild and congrats to the owner.
     
  15. tyeeslayer

    tyeeslayer Super Member

    Messages:
    2,968
    Location:
    Abbotsford, British Columbia
    I just got one of these and it does not have the UFO transistors, it has Sanyo C875E's. They look original. I wonder if these were a later model substitution?
     

    Attached Files:

  16. BLAH BLAH

    BLAH BLAH AK Subscriber Subscriber

    Messages:
    1,414
    Location:
    Melbourne. ..Australia. ..
  17. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    1,893
    Location:
    Calgary, Alberta
    I'm thinking the Sanyos might be an earlier version??....
     
  18. reddish75

    reddish75 AK Subscriber Subscriber

    Messages:
    168
    Hi, great thread, does anyone have a bom for this?

    Thanks
     
  19. Zekeman

    Zekeman AK Subscriber Subscriber

    Messages:
    2,231
    Location:
    Chicago
    Patfont. Did you identify any cap upsizing in the power supply?

    I'm restoring one of these now.
     
  20. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    1,893
    Location:
    Calgary, Alberta

Share This Page