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Beginning an AU-666 recap

Discussion in 'Exclusively Sansui' started by AnalogueBen, Dec 6, 2018.

  1. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Hello to all :)

    I've only recently acquired this amp and it was functioning fine up until I learned a valuable lesson on having my meter set to the right function (mA-ac VS mA-dc, big difference!) As a consequence I blew two outputs doing a bias setup.

    I'm gathering up info and so far have got my transistor list about right I think, so I'll post it now and see whether it looks good to go.
    Then I'd like to plan choosing caps, other components and any mods going from board to board, following the illustrations given in the service manual. Try to keep it simple and easy to use as a guide. Fyi, I'll be doing all the work myself, about to build a DBT, have a scope but never used it in anger, got a Fluke meter, transistor tester and can't understand schematics other than their symbols.

    Output Transistors~
    Original - NEC 2SD188 NPN
    Replacement - OnSemi MJ21194G NPN
    Original - NEC 2SA627 PNP
    Replacement - OnSemi MJ21193G

    Remaining transistors ~
    Original - CDC8002
    Replacement - ZTX694B
    Original - CDC9002
    Replacement - ZTX795A
    Original - XA495
    Replacement -ZTX795A
    Original - 2SC871R (E,F), (F)
    Replacement - KSC1845

    Will also order KSA1015 & KSC1815 as these could be used here in some chosen places are also good to have anyway.

    Because this amp is similar to the AU999, and many of you more experienced guys have tweeked that out, I'm starting to get excited about the little beast!!!

    Driver block F-1159 up next..

    Later
     
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  2. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    I think your transistors look good. Good luck!
     
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  3. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Will order backup driver transistors..
    Original - 2SA537 PNP
    Replacement - KSA1220 PNP
    Original - 2SC708 NPN
    Replacement - KSC2690 NPN

    New trimpots
    Bourns 3296P ( good or a vertical board)
    1K & 5K.

    Think I'll get this oder in today, that way amp can be up and running whilst cap selection is being made...
     
  4. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    These are a bit better and cheaper I think than the ZTX parts.
    CDC 8002 → KSC2690
    CDC 9002 → KSA1220
     
  5. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    IMG_5631.jpeg
    What my driver boards looked like after restore.
     
  6. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Actually, I did also order a small number of transistors you've suggested. I saw alot of mention for the ZTX's so went for them in the first place. Thanks for the pics, did you do a thread for your recap? What was your before/after impressions?
     

     

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  7. kevzep

    kevzep Its all about the Music Subscriber

    This is what I use as well.
     
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  8. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    I didn't do a thread, probably should have but I do a few restores a week lately so it's hard to find time. It was broken before I restored it so couldn't listen, the bridge rectifier crapped out.
    Very worthwhile to restore, it's an amazing amp that's easy to work on. I was sad to see it go.
     
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  9. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    @kevzep, is there any one reason you like the KSC/KSA over the ZTX's? .. I've ordered enough ZTX's for 3 Sansui amps I'll do transistor replacements. Just so long as these don't give me problems is all I'm really concerned about. Thanks
     
  10. kevzep

    kevzep Its all about the Music Subscriber

    They are a TO126 package and have better dissipation and I think higher current, and are also more readily available, but the ZTX will not cause any issues if thats what you have on hand to use.
     
  11. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    First board dismantled and here are the findings.
    Transistors ~
    XA495- 176 hfe, 710mV Vbe, 6.1 Ic
    XA495- 163 hfe, 709mV Vbe,6.1 Ic
    8002- 106 hfe, 644 mV, 6.2 Ic
    8002- 106 hfe, 644 mV, 6.2 Ic
    Driver 2SA537- 53 hfe, 659 mV, 6.1
    Driver 2SC708- 32 hfe, 616 mV, 6.1
    2SC281- 332 hfe, 651 mV, 3.0 Ic

    Caps~
    Elna 47uf- 60.1uf, 0.77 esr, 3.5 Vlos
    Elna 100uf- 141uf, 0.53 esr, 2.7 Vlos
    Mylar 1uf- 1.027uf

    Resistors ~
    All look to be within the 10% tolerance, haven't finished doing that cross check as its getting late here...

    Why pull the resistors? Because I want to be sure that it's going to be in spec, peace of mind thing. I'm guessing these are carbon film and not carbon comp ? And now that they are out do I go ahead and put new 1%'ers in there like vishay?

    Have ordered new diodes for here also (1N4848). Think I'll also order C0G type csps to replace the ceramics.
    Any cap advice or upgrades here are most welcomed!!!

    I thought to also share a little trick I discovered while at the bench.
    First was to lay a towel down on the bench as when you drop a tiny part it cushions the fall and the part doesn't end up in the corner of the room!
    Second is a real beauty, never seen it done before but it may already be used. When your flipping the board trying to find which pad to solder/de-solder and it looks like a maze!, well I grabed my lazer pointer and pointed right directly at the leg of the part, which that then shows exactly where your solder pad is underneat.. cool hey :)

    Cheers 2018-12-08 23.50.49.jpg 2018-12-08 23.48.42.jpg 2018-12-08 23.49.00.jpg
     
    Last edited: Dec 8, 2018 at 8:26 AM
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  12. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Okay guys, I'm getting there with this but its happenin slowly, mostly on part selection as I'm still new to recaping. I'm happy to go with solid recommendations because this aspect seems to take way to much time for me.

    For the lytic's I'll use nichicon KZ 100uf 25v, and 47uf 25v (both volatge ratings bumped up from 10v)

    The mylar can stay in for now.

    I've been reading the au999 posts which say to upgrade the small value ceramics in some locations to C0G type. So since there are only 5 per board can I simply swap them all without problems? I have two mounted on the back of the board.


    2018-12-10 11.35.36.jpg 2018-12-10 11.36.00.jpg

    Minus/Plus ripple filter boards ~

    Electrolytic Caps are both 100uf/50v and 4.7uf/50v. What has been shown good in these circiuts, is it in the audio or power supply path. I'm thinking Nichicon PW, KZ..?
    There is a 0.01uf ceramic and a 0.047 mylar, potential upgrades?

    Ripple filter board F-1268~

    Power suppy board yeah?
    I've noticed no bumping up the uF ratings was thinking upping the voltage so long as the replacement fits. What is another proven replacement suited to for this board?

    Thanks for your help here guys, to be honest I've got house that needs repairs done and that's my real priority, but this is just more enjoyable yet sucks up alot of my time...I'm hoping yo get my final parts order complete this week and hopefully put together by xmas ;)
     
    Last edited: Dec 9, 2018 at 8:07 PM
  13. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Tone board question..,

    On the board there are 6 caps 4x 10uf and 2x 1uf, that have their tops painted in orange and green. Looking at the parts list these caps have an "RN" suffix, and are rated at higher voltage than the other 1uf and 10uf in the amp.
    So could it have just been a way to identify the higher voltage cap when being assembled?
    Or, is it a different cap ( low leakage??..) and upon looking over the schematic only then will it's purpose be seen. But as I can't read schematics yet, I'd really like somebody to give some advice here..
    Thanks in advance :)

    2018-12-12 00.34.15.jpg

    2018-12-12 00.24.40.png

    2018-12-12 00.23.46.png

    2018-12-12 00.43.20.png

    2018-12-12 00.44.10.png
     
  14. Leestereo

    Leestereo Super Member

    Messages:
    2,142
    Location:
    Ottawa, ON
  15. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Leestereo, massive thanks for coming to the rescue here! Will go with the Nichicon ES.
     
  16. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Filter advice pretty please :)

    Just about to order parts so am wanting to make a sensible choice on the filters..
    stock ratings are 3300uf so I'm looking at replacements up to the 6800uf mark.

    With most things in life there is a trade off, what would it be if going up to this size? I understand they mainly act as a reserve for I guess higher loads/volume,
    would I sacrifice then any "soul" in the lower levels?

    Looking at these so far from Vishay..
    https://au.mouser.com/ProductDetail...n0r9vR22U%2bJu6XaAk5RiWA3QoL/tkCcCsC0ksJI7Q==

    https://au.mouser.com/ProductDetail...n0r9vR22U%2bJu6XaAk5RE2SnmtehjUArdWM3r5P0NQ==

    And CDE..
    https://au.mouser.com/ProductDetail...=sGAEpiMZZMtZ1n0r9vR22dctXbdJ0qvsMF5S4RS5hz4=

    https://au.mouser.com/ProductDetail...=sGAEpiMZZMtZ1n0r9vR22dX5NZxAiz78VbBO0/ff7K0=

    https://au.mouser.com/ProductDetail...=sGAEpiMZZMtZ1n0r9vR22dctXbdJ0qvsHN7fx2jgARk=

    Thanks a billion!!!!
     

     

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  17. AnalogueBen

    AnalogueBen Member

    Messages:
    65
    Quite sure now that I'll go with the CCE381lx @ 4700uf.. I don't want to get to greedy as I'm no expert at identifying those potential cause/effect changes. This is the only place where the Uf is bumped up, and with every other lytic cap being replaced I'm sure there will be plenty "new life" brought to this bad boy :biggrin:
     

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