Perfect 9090 DB need volume Pot

Discussion in 'Exclusively Sansui' started by ppanther, Jan 7, 2018.

  1. ppanther

    ppanther New Member

    Messages:
    7
    About 5 years ago my dad gave me his perfect Sansui 9090 DB he purchased while in the military in the late 70’s. He never let me touch it as a kid but never really ever used it either. Before he gave it to me, it sat for at least 15years without ever being turned on. It has probably been used less than 100 hours in its life. I got it from him along with the original Pioneer speakers that he purchased with it. The speakers are perfect as well. I hooked it all up and everything worked except for the volume. I only have good sound on both speakers at 1/4 and 3/4 volume. I put the amp in the shop but the pot could not be saved. I have been looking for a used volume pot for 3 years now.
    Any ideas how I can get this great sounding amp going again.

    Thanks.
     

     

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  2. tnsilver

    tnsilver AK Subscriber Subscriber

    Messages:
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    I am curious. Why, what could have destroyed a volume pot of a 100 hours run in unit? Have they tried to just DeoxIT the pot?
     
  3. sKiZo

    sKiZo Hates received: 8641 Subscriber

    I'd also check to see if it's the infamous dolby board issues. That could happen with age ...

    FIre it up and try cycling all the push buttons and see if you get intermittent results. And yes, I'd try a real good cleaning before replacing the switch. Can't remember how much disasssembly is required to get good access, but a light spray of DeOxit in all the access holes in the switch and work it slowly to the stops several times. Put the receiver on it's side and repeat, then same with the other side to ensure good coverage of all the internals.
     
  4. ppanther

    ppanther New Member

    Messages:
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    I tried the cleaning process first with no help. Put in the shop and they took the volume pot apart and said the disks in the pot had corrosion and would not clean up.
     
  5. ppanther

    ppanther New Member

    Messages:
    7
    My high school graduation present was a Kenwood system with a KA-94 amp. I have hundreds and hundreds of hours on this amp and have went through several speakers. The Kenwood volume pot started acting up this year. I cleaned one time myself and it works perfect again. Wish the Sansui was this easy.
     
  6. JRC75

    JRC75 Active Member

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    Location:
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    search "rebuild potentiometer". All my old equipment the pots get cleaned and lubed to maximise life. Sounds funny that its dead. Also there is a site I ran across I think mikes something, he bought out repair shops years ago and sells or rebuilds pots. I will post if I can find it. What does the 9090 pot look like?
     

     

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  7. LBPete

    LBPete Rolling Along Subscriber

    Messages:
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    The volume pot is often blamed for channel dropout that is occurring elsewhere in the pre amp. It is possible that at some point in its 40 years of life, someone tried cleaning it with something nasty. I've seen all kinds of home remedies used on volume pots in an attempted to fix routine channel dropout. The only source for a replacement is from donor unit. The pot from a 8080, 8080DB, 9090 or 9090DB will work. I'm pretty sure a 7070 will work too.

    Please post the serial number for the database. Click on the link in my signature block.

    - Pete
     
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  8. ppanther

    ppanther New Member

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    Thanks. I will Update in data base.
     
  9. KingBubba

    KingBubba "Too Much Stuff"

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    Is the pot still in the unit? If not, do you have all the parts? Read the sticky post about the use of Deoxit on AK. If the pot is still in the unit, use Deoxit and do a good cleaning, after which check your operation and see if it has improved. Some pots need more than one cleaning to clear the corrosion.
     
  10. Tom B

    Tom B AK Subscriber Subscriber

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    Location:
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    ppanther,
    I used to have a spare 9090 control. I will look around and see if I can find it. I am a bit concerned for you about the shop "taking the original control apart" Dismantling one of these is not an easy task. They are a 4 section control with 2 of the secions having a loudness tap. The shaft is secured at the end by mushrooming the end part of the shaft to keep all 4 sections together. (I believe this is how there are assembled) to take it apart requires removing the "Mushroom" but reassembling after this can be sometimes an impossible challenge, because there may not be enough metal at the end of the shaft to recreate a mushroom. I will tackle almost any job, but when I developed a mechanical issue with the control in one of mine, I examined the assembly and quickly realized I didn't want to attempt the dismantle because of the design. I bought a replacement and installed it.
     
  11. ppanther

    ppanther New Member

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    Thanks very much. I used Jots electronics in Arlington texas. They seemed very knowledgeable.
     

     

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  12. tarior

    tarior Dirty pool, old man? Subscriber

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    Sounds fishy to me. In nearly 15 years of working on stereo equipment, 6-1/2 years of which I had a full time brick and mortar shop, I can count on one hand the number of volume/balance/bass/treble pots that were so bad that they had to be replaced. IIRC, none of them were on Sansui. Both hands if I include rotary encoders from newer gear.
    I would be very suspect of their troubleshooting and repair methods.
     
  13. ppanther

    ppanther New Member

    Messages:
    7
    Cleaned the volume pot this morning with Deoxit but did not help. Still have almost no sound on right channel at most volume levels. While I was trying to get the right channel to work, I started cleaning the dust from the front display. I noticed when I touched the “low or high filter buttons”or the “audio muting” button the right channel would have sound. After messing with these buttons I figured out that if I pushed up on any of these three buttons, the sound was perfect at all volume levels. I now have a tiny screw driver wedged below the low filter button and the sound is perfect at all levels on both channels. I have had it like this for 2 hours.

    Any ideas what I need to do to repair.

    Thanks.
     
  14. tarior

    tarior Dirty pool, old man? Subscriber

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    De-Oxit every single pot and switch on the unit. Replace the speaker relay. Replace all of the fusible resistors, and VD-1212 diodes. Replace the bias trimmers. Pin all of the feedthroughs on the Dolby board. In more or less that order, just for starters.
     
  15. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I am glad you see now how very wrong the 'Shop' was that told you the volume control had failed.

    Obviously you need to clean those switches - but as far as I remember this requires a considerable amout of dismantling of the unit, during which you could do the jobs tarior has suggested above.
     
  16. LBPete

    LBPete Rolling Along Subscriber

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    Virtually every knob or button on that face plate has a switch or a potentiometer behind it. If dirty, almost any one of them can cause the symptoms you are having. The fact that moving some causes the sound to come and go illustrates this fact. You have to get cleaner like Deoxit D5 into every one of those switches and pots. It takes some disassembly to get access to do that. If you don't feel comfortable disassembling and reassembling stuff, you probably should leave it to a pro.

    - Pete
     

     

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  17. LBPete

    LBPete Rolling Along Subscriber

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    I had forgotten that this thread started with the work of a "pro." Time to find a different one.

    - Pete
     
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