Having some issues with a recently acquired Sansui 9090DB

Discussion in 'Exclusively Sansui' started by stereo_dog, Nov 23, 2014.

  1. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    I "inherited" a Sansui 9090DB from a friend a few weeks ago, unit was/is pretty dirty, was in a garage environment most of it's life. Brought it home, plugged it in connected it to a cheap pair of speakers, and it had all kinds of static, drop-out in sound, etc. etc. Took it apart, cleaned all the switches, buttons, etc. Worked all the switches, buttons and applied some Faderlube. Put it back together enough to plug it in and fire it up.

    First, I checked the DC Offset for both channels per Echowars tutorial. Right was at 7-8 mV and Left was 3-5 mV. Both bounced around a little, even after 10 minutes or so. That looks pretty good. Plugged in some speakers, connected a CD player, and fired it up. Actually it sounded pretty good, some static still in the controls, but gently worked them out.

    Played it out for around 30-40 minutes, then noticed a drop in volume in the right channel. Went through and worked the controls a bit more, and noticed when I took the unit out of stereo mode into mono mode, the volume increased in the right channel up to the left channel level. Played around with this for another 30 minutes or so, no change. Swapped the speakers to make sure it was not a speaker issue, same results, right channel noticeably quieter.

    Before I take the unit apart and go through another cleaning cycle, I thought I may ask some more knowledgeable folks if I should be looking for another cause.

    Any clues or theories would be appreciated.

    As an aside, my goal when I took this receiver was to return the unit to my friend in a better working and "cleaner" condition, even though he thinks I'm keeping it.
     

     

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  2. Double T

    Double T AK Subscriber Subscriber

    Messages:
    41
    You did not mention the AM and FM positions on the mode switch are they following the same right channel reduction? DC Offsets still the same? The Dolby switch is known to cause problems as well as most of the push button switches on the front panel, don't forget the speaker selector switch.
     
  3. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    No, the only switch that is causing the problem is the stereo/mono switch. I've cycled through all of the switches individually, no other issues.
     
  4. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,716
    Location:
    Long Beach, CA
    When you push the mono switch the signal from the preamp is blended together and fed to both amp channels. If the volume changes, the problem is in the preamp before the mono switch. Keep cleaning.

    - Pete
     
  5. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    Thanks. Keep cleaning the switches, push buttons, correct?
     
  6. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,716
    Location:
    Long Beach, CA
    Yes.

    - Pete
     

     

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  7. canuckaudiog

    canuckaudiog On a quest for high fidelity

    Messages:
    7,793
    Location:
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    I'll second that. I had the same issue on a Sansui AU-555a and cleaning the switches fixed it.
     
  8. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    OK, thanks.
     
  9. nosirrah

    nosirrah Moderator Staff Member Moderator Subscriber

    Messages:
    7,487
    Location:
    30 min north of seattle
    Focus on the selector switch. I did a 990 {non-db} and it took a lot of work to get it going properly.
     
  10. titanstats

    titanstats Go Habs Go!

    Messages:
    4,413
    Location:
    Vancouver
    +1, clean, then clean again. Sansuis have always seemed to have the most difficult controls to get clean, at least to me. Had a 717 that was just the devil to clean a few buttons on, particularly the switch on the back.
     
  11. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    Thanks everyone. I appreciate all the encouragement. Been out of town for the holiday, but I will get back to cleaning, shortly. What I heard, so far, sounded really good. I have a G9000, myself, and have always like the sound from The Sansui's.
     

     

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  12. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    Well, I'm back on the 9090 after a long absense. I've cleaned the switches a total of 20 times, went through (2) cans of Deoxit. Played it out this morning and after about 20 minutes, the right channel drops out, again. Put it in mono mode, channel comes back.

    Is there anything else I should look for?
     
  13. grateful

    grateful Super Member

    Messages:
    3,052
    Location:
    Mass
    2 Cans of Dexoit is way too much. Hopefully, that has not damaged the pots. Suspect the Dolby board. Jiggle the tape monitor switches to check for intermittency , filter switches and any other that the preamp signal passes through.
     
  14. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    Thanks for the advice. I really didn't use (2) cans..... just frustrated when posting this morning.

    I have tried jiggling all the switches one at a time to see if it helps/hurts, the only one that brings both speakers back is the mono switch. Does that circuit go through the Dolby board?
     
  15. grateful

    grateful Super Member

    Messages:
    3,052
    Location:
    Mass
    Yes it is always in the path. There are threads on AK regarding restoration.
     
  16. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    OK, so far, so good. It's been playing out for several hours on a variety of sources, sounding very good with no apparent issues, so far.

    Thanks to everyone for their advice.

    A couple of quick photos:

    [​IMG]

    [​IMG]

    [​IMG]

    Cleaned and oiled the case, cleaned and polished the facepalte and knobs, etc. Looks pretty good. The interior was black from smoke and years and years of dust and dirt.....

    If it holds up, I'm going to take it back to my friend and surprise, him.
     

     

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  17. onemug

    onemug AK Subscriber Subscriber

    Messages:
    2,989
    Location:
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    Looks nice. Glad it's working.

    Curious...what did you use to polish the knobs?
     
  18. stereo_dog

    stereo_dog Well-Known Member

    Messages:
    981
    Location:
    Northeast Indiana
    "Original Bike Spirits" cleaner & polish. The same stuff I use on my motorcycles. Then I used a toothbrush to get into the ridges on the knobs. Works really well, very gentle on the silk-screen lettering.
     
  19. onemug

    onemug AK Subscriber Subscriber

    Messages:
    2,989
    Location:
    Southern California
    Thanks. Nice dog in your Avatar.
     
  20. Wadester999

    Wadester999 New Member

    Messages:
    12
    Stereo Dog, you never told us what was the fix. Was it just continued cleaning?
    I'm having a similar problem on my 9090DB but i'm pretty sure it's in the amp section as switching to mono does not make it play on both channels.
     

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