New project. Sansui 8080 recap. Advice appreciated.

Discussion in 'Exclusively Sansui' started by RR--, Apr 4, 2018.

  1. Hipocrates

    Hipocrates Anti-Muppet

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    Just in case... This is the star grounding, since we have corrosion problems, It will be wise to check it.
    upload_2018-4-27_17-32-22.png
     
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  2. RR--

    RR-- Active Member

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    I'm not sure, I put some Loctite on the ground star screw so it's on really tight. The solder joints are really thick too. I cut the extra tabs off the capacitors and insulated them with electrical tape just to be sure.
    How would you twist the wire with a drill? So they wrap around each other several more times?
     
  3. Hipocrates

    Hipocrates Anti-Muppet

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    On the inside can be some corrosion, but that's just an idea to explain some hum.
    Regarding new wiring...

    As we can see, this is not optimal, can lead to problems, (it is too close)

    upload_2018-4-27_18-51-31.png

    That's why I tend to use new wiring for applications like that, the soldered joints would be less stressed and we will have a cleaner and safer installation.

    Regarding the twisting, as we saw those wires are susceptible to produce noise.
    https://en.wikipedia.org/wiki/Twisted_pair

    Off course, it is debatable about how much twist is require.
    I just do it like this
     
    Last edited: Apr 27, 2018
  4. RR--

    RR-- Active Member

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    Fair point. I'll get onto that this afternoon then, after that it's the output transistors.
    I also just finished recapping the phono board, the Wimas sure make it easier.

    [​IMG]
     
  5. Hipocrates

    Hipocrates Anti-Muppet

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    Remember to adjust after the new outputs.
    The unit is almost done! Cool!
     
  6. RR--

    RR-- Active Member

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    Hey quick question, should the legs for the transistors be clean or covered in thermal compound? When I removed the old ones the holes are full of thermal compound, not sure if I should clean it all out or not.

    [​IMG]
     

     

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  7. Hipocrates

    Hipocrates Anti-Muppet

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    They need to be clean, use some WD40 to remove the old paste... just a small, thin well spread amount will do the job, too much is not good.
     
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  8. RR--

    RR-- Active Member

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    More questions. New output transistors are in, the Bias is dead on 30mv but the DC Offset now can only be adjusted between 50 and 80mv where the manual states it should be set to 0mv +/- 10mv. The amp still clicks through protection if it's around 50mv.
    Thoughts?

    [​IMG]
    [​IMG]
     
  9. Hipocrates

    Hipocrates Anti-Muppet

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    How was the offset previously?
     
  10. RR--

    RR-- Active Member

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    Very touchy and difficult to adjust but I had it within 5mv of 0mv before the recap.
     
  11. Hipocrates

    Hipocrates Anti-Muppet

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    Can we confirm volume at zero, tones and loudness 'off" AUX input and nothing connected?
     

     

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  12. RR--

    RR-- Active Member

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    Oh I'm an idiot, I had the speaker selector off! haha.
    I started that habit just in case anything surged.
     
  13. Hipocrates

    Hipocrates Anti-Muppet

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    :rflmao::rflmao::rflmao:...I was like this:yikes:
     
  14. RR--

    RR-- Active Member

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    New ground cable in, your drill trick worked a charm. It didn't make much of a difference though, it has this constant electrical noise hiss with a slight ground like hum, I'm not sure if I'm just spoilt by the AU719, one thing I like about it is I can leave it one all day with nothing playing and not be able to hear any noise. My AU719 was pretty bad before it was recapped and was annoying to leave on.

    Interesting to note, touching the chassis with my hand makes the hum a little quieter also the Audio Muting -20db switch pressed in makes the hum disappear even with the volume close to maximum.:dunno:

    [​IMG]
     
  15. Hipocrates

    Hipocrates Anti-Muppet

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    Are all the hex nuts and screws of the front end boards in place?
    Check for any loose black wire.
     
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  16. petehall347

    petehall347 the brandy coffee man Subscriber

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    try with the metal covers loosely fitted if you haven't done already .
     
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  17. RR--

    RR-- Active Member

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    You guys deliver yet again! :thumbsup: After tightening every screw and properly attaching the faceplate and baseplate the hum vanished. I still had it in pieces as I was waiting for some painted pieces to dry.
    I'll tackle filing down that faceplate trim this week and order a couple more parts, might even install that switch. VU incandezcsnt bylbs are in the mail too.

    Unfortunately I tried to compare it with my AU719 only for it to get stuck back in protection mode for the first time in a year. I paid a professional a small fortune to fix that too. When I recapped it I didn't replace the relay so hopefully that's all that needs doing.
    Right when I think I'm finished too haha.

    Thanks again for all the help and advice, I wouldn't have gotten this far for sure by myself.
     
  18. Hipocrates

    Hipocrates Anti-Muppet

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    Just as clarification, witch unit is in protection mode?:(
     
  19. RR--

    RR-- Active Member

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    The AU719 is in protection mode again. The 8080 is working beautifully!
     
  20. Hipocrates

    Hipocrates Anti-Muppet

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    Phew!!... Worry not, It looks that the protection circuit is doing his job. That's usually the drill with Sansui, they will have some issues until is properly reconditioned (like you did with your 8080).
     

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