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Strange sound - Sansui AU317

Discussion in 'Exclusively Sansui' started by stians, Nov 8, 2018 at 4:39 AM.

  1. stians

    stians New Member

    Messages:
    25
    Location:
    Oslo, Norway
    Hello

    I have a recapped Sansui AU317, and it sounds really good. When not in use (but powered on), it suddenly "pops" and a high pitched sound appears decreasing down to a lower tone (I can hear the pulse (40-50hz maybe)), then disappearing. It takes 2-3 secinds. It works well before and after and I have never experienced it during use. I believe it's only in the right channel, but not sure.
    Anyone familiar with this problem?

    Regards
    Stian, Oslo
     

     

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  2. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    18,729
    Location:
    Cleveland, Ohio
    It is probably a noisy transistor. Next time it does this, turn the volume down and see if it affects it. If the sound stops when you turn the volume down, the problem is in the power amp. If not, it's in the preamp.
     
    slimecity and stians like this.
  3. inductor

    inductor Super Member

    Messages:
    1,572
    Location:
    uk
    most of the small transistors are going faulty in these nowadays, in the phono and tone sections
     
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  4. stians

    stians New Member

    Messages:
    25
    Location:
    Oslo, Norway
    Thanks guys, I'll try being quick next time it happens :)
    Could it be a problem in the phono-stage? I don't remember whether it only appears on phono or all. Will check it out tonight.

    Regards/ Stian
     
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    47,972
    Location:
    Hertfordshire, UK
    From previous experience any of the transistors in the 'Control Amp' could cause this issue, for the right channel this will be TR2,4,6,8. Or the dual diodes (VD1212) found in both the Control Amp and the Phono (Head) Amp can be troublesome.
     
  6. stians

    stians New Member

    Messages:
    25
    Location:
    Oslo, Norway
    Thanks a lot. Are these transistors/diodes still possible to obtain?

    Regards /Stian
     

     

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  7. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    47,972
    Location:
    Hertfordshire, UK
    The original type numbers have very likely not been made for decades, but there are modern substitutes which work as well, or better, than the originals.

    Today for example, we would replace the VD1212 dual diodes with 2 x 1N4148 diodes connected in series. For TR02, TR04 & TR06 we would use KSA992 and for TR08 we would use KSC1845, there are others but these type numbers are the most commonly used replacements. Elsewhere on AK there is a thread devoted entirely to old type number semiconductors and their modern readily available replacements. ;)

    Do some searching and reading around AK, there is much information about the AU-317 including threads describing how to recondition them in some detail.
     
    Last edited: Nov 8, 2018 at 1:56 PM
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  8. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    18,729
    Location:
    Cleveland, Ohio
    Sorry, I meant to say that if the sound goes away when you turn the volume down, the problem is in the preamp.
     
    Hyperion likes this.

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