AU-999 Restoration & Modification

Discussion in 'Exclusively Sansui' started by leray1, Jan 12, 2019.

  1. leray1

    leray1 AK Subscriber Subscriber

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    I think I'll leave the transistor. The diode on the other hand has corrosion, or something, on its legs. My guess is that I use two of the 1N4004 and orient them according to the markings on the 10DC1R, i.e., the current flowing to the middle leg, so I would put the negative ends of the diodes facing each other with the negative leads in the same hole (middle hole)?
     

     

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  2. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    Usually there is no need to replace those, they do their job pretty good.
    MUR1620CTR, can be considered an update , or if you want the 2 1N4004 connected by anode.
    I leave 2SD223 alone too.
     
  3. leray1

    leray1 AK Subscriber Subscriber

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    I put the 10DC1R back in and left the transistor, too. See pics of diode

    Man, that board is a pain to wire back in place. Yeesh. I also realized I have a mistake on my parts list. I need to order another 493-1924 (4.7/63) as I had one of them listed as 493-1936 (100/63). I'm embarrased to say it, but this will be my eighth or ninth order for this project. The shipping is killing me. :( And, now the end is delayed, again. I was planning on wrapping it up this weekend, if not sooner. Oh well, it will be worth it.
     

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  4. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    The 10CD1R clean up nicely.
    That's why from my point of view is always better to create your own lists and the the provided as a guide. It helps to get familiar with the unit and to learn.
    Tell me about it
    For small orders digi-key is less expensive, I think 3.75, plus taxes, for bigger orders I use mouser, but lately they are charging me 3x more than before.
    Then I have to pay shipping to Costa Rica and 40% import taxes ಠ_ಠ
    For me, to have a stock of parts make sense because it comes all the way to Costa Rica, have a lot projects and like to test components as experiment.
    Otherwise I would have to use Teapo, ICC or Cheng caps or chinese transistors ಠ_ಠ
    Funny thing, just shipping cost sometimes is less expensive to ship from Miami to Costa Rica that some US places to miami.
     
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  5. leray1

    leray1 AK Subscriber Subscriber

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    Got the C621 and bias transistors replacements today. Just installed them and all is well (dim bulb). I'm just waiting on a cap for one of the ripple boards and I'll be done. Actually I'll probably do the bass eq mod in the meantime.

    For the transistors, I soldered the leads off of the 2SC281's onto the leads of the KSC1815's and added a little insulation from some wire I had on hand. Not pretty but functional. The bias transistors are making contact with the best sink sleeve but should I crimp the sleeve for the best contact?

    20190206_175747.jpg 20190206_181616.jpg 20190206_184050.jpg 20190206_184935.jpg
     
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  6. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    Are you using KSC1845 instead 2SC281? IF that so, check the pinout, KSC1845 is ECB.

    I think you can use a little bit of thermal paste and try to fit it the best you can.
     
    Last edited: Feb 6, 2019

     

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  7. leray1

    leray1 AK Subscriber Subscriber

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    No, KSC1815.
     
  8. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    [​IMG]
     
  9. stereofun

    stereofun Super Member

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    Thumbs up - Looks good. Could you possible fit the ksc1815 inside the old sleeves of the 281's (provided you can separate or hollow out the sleeve) . Say the rounded side up against the curve of the sleeve, then fill in some resin / JB weld etc in the remaining gap, that way the 1815 would fit perfectly into the receiving sleeve coming off the heat sinks. If not, I guess a little tug on the receiving sleeve might do the trick, just get the most contact as possible as these are bias feedback transistors,relying on the heat transferred to them from the heat sink.
     
  10. leray1

    leray1 AK Subscriber Subscriber

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    Thanks, I'll give it a try
     
  11. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    But isn't collector connected to base on the board and base connected to collector on the board ?
    [​IMG]
     

     

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  12. leray1

    leray1 AK Subscriber Subscriber

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    I think you're right. I thought the base was in the middle. Thanks
     
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  13. leray1

    leray1 AK Subscriber Subscriber

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    I've got the 2SC281 housing hollowed out. The epoxy I have can withstand temps up to 180F or 82C. Is that enough or do I need something else? 20190207_174836.jpg
     
  14. stereofun

    stereofun Super Member

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    That's more than enough...
     
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  15. leray1

    leray1 AK Subscriber Subscriber

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    This evening I got around to correcting the bias transistors' pinouts and put them in the old transistors' housings. I didn't use epoxy, just thermal compound inside.

    I also did kevzep's bass eq mod. My apprehension was well founded as it was not easy.

    I also took out the + Ripple Filter (F-1231) board and changed C813 and TR823. I'm just waiting on C815's replacement. It should be here tomorrow (although tracking wasn't updated today). Fingers crossed... 20190208_201619.jpg 20190208_201651.jpg
     
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  16. stereofun

    stereofun Super Member

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    Kevzep's Bass EQ mod, is for soldering skill what a 20 kt crosswind landing is to a pilot.

    You passed !
     

     

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  17. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    Nice work!
     
  18. leray1

    leray1 AK Subscriber Subscriber

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    Thanks! It doesn't look great but the joints are sound.
     
  19. leray1

    leray1 AK Subscriber Subscriber

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    I finished up this afternoon, set offset and bias on, and then off, the DBT - all good.

    I've been listening to music off of my phone on AUX through headphones. It sounds great but...

    Switching between inputs causes a click/pop most notably between AUX and PHONO2 (it did this before I did any work on it, but it seems a more noticeable now, maybe).

    There is a loud hum when Source Selector is on PHONO2, PHONO and MIC - there was nothing connected to these when testing, there is no hum on AUX.

    Touching the Volume button creates a very low hum that's only noticed if there is no music playing.

    All of this was done without any of the covers on.
     
  20. stereofun

    stereofun Super Member

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    The phono board has two types of transistors, one set compared to the other is in some weird mirror wise config that makes it easy to pin out wrong - if the replacement tranny's pin out are different too.....so double and triple check those.

    Test again with covers on and after thorough inspection of phono board pinouts.
     

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