How to bypass the Dolby board on a Sansui 9090db?

Discussion in 'Exclusively Sansui' started by z-adamson, May 16, 2018 at 3:19 PM.

  1. z-adamson

    z-adamson AK Subscriber Subscriber

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    I am assuming this can be done.

    From what I gather, you lose tape in and out.

    All I will use is AUX, so....non issue.

    Has anyone bypassed this board before?

    How would one go about bypassing the Dolby board?
     

     

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  2. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Luck with that ... most of the audio gets routed through that thing at one point or another as it also controls the entire ganged bank of pushbuttons to the right of the volume control. I suppose you COULD try just hard wiring the AUX input on the back directly to the preamp section, but I'm thinking that would leave you with basically a bare bones integrated amp. I believe tone and channel balance and such are also gone if you do that. Terrible waste of an excellent feature rich machine ...
     
    Last edited: May 16, 2018 at 3:31 PM
  3. dpcornell

    dpcornell Member

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    I will save you the search time: the answer is 'no'.
    I just pinned my dolby board and it took about 5-6 hours (not including the two I missed the first time around). It is worth the effort.
     
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  4. tnsilver

    tnsilver AK Subscriber Subscriber

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    I read it can be done, I'm sure it can be done, in theory it must be possible to be done, but in practice I've never heard of anyone who's done it, even though I'm sure they can.
    Easiest way would be to pull out the main-in/pre-out jumpers and plug whatever source directly to the amp. No Dolby circuit. Voila! Good luck with any other way.
     
  5. z-adamson

    z-adamson AK Subscriber Subscriber

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    I read on here about a guy that "had it done" and lost tape in and tape out.

    No info beyond that.
     
  6. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Ever SEEN the board of which we speak?
    (shudder)

    [​IMG]

    PS ... seems to me that relay is an integral part of the protection system as well. Lose that, and lose the amps as well. Be interesting to see a link you're referencing to show exactly what's being successfully bypassed - I'd suspect they're just talking the dolby section itself? That looks like it'd be doable, but that's usually not the reason anyone ever considers working on the board ...

    And yes - I've pinned and refurbed a similar board on my QRX 9001 - not a job for the faint of heart!
     

     

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  7. z-adamson

    z-adamson AK Subscriber Subscriber

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    This is the board I am talking about...
     

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  8. lbcgav

    lbcgav AK Subscriber Subscriber

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  9. tnsilver

    tnsilver AK Subscriber Subscriber

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    yup, the dolby board is all too well known I'm afraid, it's the switch board we referred to that's connected to it.
    Is this yours? If you got it out like this, it would be way easier to service it than bypass it.
    There's an excellent dolby board overhaul sticky by Pete in this forum.
     
  10. kevzep

    kevzep Its all about the Music Subscriber

    Why not just service it and have it running as intended by Sansui?
    The board is integral to the amplifier, and bypassing, which will be more of a complete headache, more time consuming than servicing it, and a bigger PITA than you can imagine.
    Bypassing it will severely reduce the resale value too, I for one would not want to buy a bastardised 9090DB...

    Just fix it...
     
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  11. sKiZo

    sKiZo Hates received: 8641 Subscriber

    I did find this, and apparently you can bypass just the dolby section, leaving the switching functions intact. No reference to exactly how it's done without losing a LOT of other features as well.
    http://www.audiokarma.org/forums/in...in-sacramento-california.677925/#post-9052083

    Not sure if QRXRestore is back up and running since Jim died, but be worth checking.
    (RIP @Trnsfmr ... you ARE missed. )

    There's also a note in the same thread that suggests leaving the tape loop alone (and disabled due to the dolby bypass) and rewiring one of the phono in sections? That opens yet another can of worms, and wouldn't give you a true loop for recording anyway. I also see some reference in the same thread about losing a lot of gain ... never a good thing in my world, as it probably puts you out of the receiver's "sweet spot".

    And once again - it's not the dolby section that's the usual culprit, and that can be bypassed already with the twist of the wrist. Again, be interesting to know exactly what the "problem" is here ...
     
    Last edited: May 16, 2018 at 4:32 PM

     

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  12. kevzep

    kevzep Its all about the Music Subscriber

    But the reality is, it is far easier to just service the board than trying to mess about with something which will be more time consuming and cause you more headaches...
     
  13. sKiZo

    sKiZo Hates received: 8641 Subscriber

    See "rube goldberg" ... <G>
     
  14. z-adamson

    z-adamson AK Subscriber Subscriber

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    You bring up an interesting idea.

    Could you or anyone else in the know provide any insight as to how exactly to do this and what exactly will be lost?

    I am not seriously considering this, but I may if there is a way to keep tone controls, loudness etc.
     
  15. z-adamson

    z-adamson AK Subscriber Subscriber

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    I understand the advantage to keeping it working as intended. But, sometimes things need to be changed for a variety of reasons.
     
  16. kevzep

    kevzep Its all about the Music Subscriber

    Totally your call, but its unnecessary as the problem can be resolved a lot easier than what you are proposing, I have done a few Dolby boards on the QRX9001's and they are even worse than the 9090, and I don't find them to be an issue at all really....
     

     

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  17. z-adamson

    z-adamson AK Subscriber Subscriber

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    Interestingly, that shop is only a few hours from me.

    They only charge $45 for this mod (bypassing the dolby).....so how big of a job can it be?
     
  18. kevzep

    kevzep Its all about the Music Subscriber

    They've done all the hard work already, the PITA part is figuring out the best way to do it. Once the formula is established its pretty easy.
     
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  19. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Yup - if you're within driving distance and they're up for business, that'd be the way to go. I know S&H can be a killer for a unit that size, and I wouldn't want to mail it without some seriously bulletproof packaging.
     

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