Sansui 331 intermittent right channel

Discussion in 'Exclusively Sansui' started by adamp, Apr 3, 2017.

  1. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    I'm more of a vintage Marantz guy but couldn't pass up a cheap Sansui 331 last weekend. I went to pick up a pair of Marantz Imperial 7 speakers and the guy included this 331 for $10....

    All of the bulbs were burned and all of the controls were super crackly. I took it apart, replaced the fuse lamps, deoxit-ed all the pots and switches. Hooked up to a pair of Dynaco A-35s and a Marantz 6100 turntable in my bedroom, this thing sings......

    ....Except that the right channel will intermittently cut out. Sometimes after five minutes, sometimes after three album sides. Playing with the controls seems to have no effect on it, but powering the receiver off and then back on will bring the dead channel back. Even when it is not working, if you turn the balance all the way to the right and turn up the volume, it does faintly produce sound on the right channel.

    I'm not an electronics tech, but an auto mechanic/electrical diagnosis tech by trade, although I must admit that my knowledge and experience with semiconductors and capacitors is somewhat limited.

    Armed with a multimeter and the schematic diagram, is there a common thing I should be looking at first that anyone knows about?

    Thanks in advance,

    Adam
     
  2. mroboto

    mroboto Super Member

    Messages:
    1,250
    Hello,

    I suspect the speakers protection relay.

    You can replace it or clean contacts after removing it from the circuit with toothbrush and Brasso and finish with alcool and water.

    Be careful to not break the wires on both sides of the coil.
     
    Last edited: Apr 3, 2017
    moefuzz likes this.
  3. moefuzz

    moefuzz Active Member

    Messages:
    351
    Location:
    Peeyong Bangyou
    .
    On relays etc.
    Just remember that as with any contacts, you are polishing the contacts/relays and not sanding in anyway shape or form..
    - you do not want to imbed grooves into the face of the contacts as even the most microscopic scratches will cause arching and you will be worse off very shortly after you have "repaired' your girl. -Polish the surfaces to a smooth and shinny finish.....

    Sincerely,
    moe jong un
     
    Last edited: Apr 5, 2017
    Ben g. likes this.
  4. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,192
    Location:
    Victoria, Australia
    Hi, the 331 doesn't utilise a speaker protection relay. They are a nice little unit as you have found out, l have a 441 that l use often. The 331 uses an STK amplifier module instead of discrete components in the amplifier section. I would first check all soldered joints and reflow any requiring attention.

    If you can't find any bad soldered joints you will have to get a schematic and see if the signal is being lost in the preamp section
    Could be a bad capacitor, transistor or an out of spec resistor etc that is sensitive to temperature change, freeze spray is good for determining this. Normally when the STK modules go they just die completely but still a possibility.

    Let us know what you find.
     
  5. Ben g.

    Ben g. New Member

    Messages:
    7
    I have been a Sansui guy my entire life. I have owned a 331 for forty years. I just bought a pristine 881.. there is no sound like Sansui sound. The xx1 line is awesome. They have a certain brilliance that you can't put into words. Its just "constant quality". Your ears never have to search for it. Its just an "in your face". Sound ...outstanding constant separation between highs, lows, mids and voice. Thank God I don't live in an apartment anymore. Had several noise complaints from my Sansui... Long live these receivers!!!
     

    Attached Files:

    Oldsansui441 likes this.
  6. Ben g.

    Ben g. New Member

    Messages:
    7
    All the xx1 Sansui are awesome.
     
  7. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    Thanks for the input, guys....

    At some point over the weekend, I'll open it back up and look for broken/loose/cracked solder joints, bulging capacitors, burned resistors, etc.

    It seems to work more reliably once it's been powered on for a while and is nice and warm.

    I'll let you know if I find anything!

    Adam
     
  8. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,192
    Location:
    Victoria, Australia
    Yes l am interested in what you find, hopefully it is something simple.
     
  9. quaddriver

    quaddriver 120 What's per channel Subscriber

    Words like warm, power back on etc point a little urgently at some solder joints that need a touch and go.

    warm = uneven expansion that forces a mechanical connection (and causes what we call 'cold joints') and power on = power surge = small sparkies that make a short term connection.

    plastic swizzle tapping everywhere....any changes? a KR4070 I just did was super plagued with cold solder, including a demonic 5 way solder connection in the RF section that would drop FM signal in spurts after an hour or so...

    I just picked up a pretty 331 tuesday I hope to crack open next week. Why I am ultimately a pioneer fan, always had a soft spot (head or heart?) for the xx1 series.
     
    Ben g. likes this.
  10. Ben g.

    Ben g. New Member

    Messages:
    7
     
  11. Ben g.

    Ben g. New Member

    Messages:
    7
    Every good ear has a soft spot for the Sansui xx1 line..
     
    Oldsansui441 likes this.
  12. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,002
    Location:
    Calgary, Alberta
    If you can't find freeze spray, you can buy cans of compressed air and turn the can upside down...Works very well for much less!
     
  13. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    Today, I set it up on the kitchen table (with a pair of Wharfedale 420's, it sounds awesome, btw, haha).

    With the covers off, I started poking around with a wooden chopstick when the right channel cut out. Capacitor C26 was the culprit! applying pressure to it with the chopstick would bring the right channel back. The solder joints looked very solid and there was no visible movement in them, so I removed the cap (and its left channel counterpart, C25...

    The one from the faulty channel is visibly more bulged and appears to be leaking. In the pic, the one from the bad channel is the one on the top.

    I'll visit my local electronics supply store at lunch tomorrow, hopefully they stock these and I can pick a couple up, install them after work and report back as to whether the problem is solved.

    Thanks for the input, guys.... I'll let you know how it goes!
     

    Attached Files:

    moefuzz, Oldsansui441 and The Fuxtor like this.
  14. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    Correction; that should read that the one from the bad channel is the one on the right, not the top.
     
  15. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,192
    Location:
    Victoria, Australia
    Nice find, well done, yes the cap on the right does look very bulged. Those are just a standard Elna cap so you can replace with a standard type cap, no need to worry about low leakage, low esr etc.
     
  16. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    Thanks for the input.

    I have no idea if they're going to be expensive.... but on Amazon, I can order a 10pk for $1.95. So hopefully they aren't much more than a couple bucks each at the local shop. This thing is in kind of cosmetically rough condition, but for $10 plus a couple of caps (hopefully), it's going to be a great little receiver for someone, and a great learning experience for me.

    Adam
     
  17. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,002
    Location:
    Calgary, Alberta
    Probably be a buck and a half at a local shop... Peanuts
     
  18. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,192
    Location:
    Victoria, Australia
    Yeah it will make a great receiver for someone and well done to you for saving it. They would be less than 50 cents each here in Australia, not sure where you are but they won't be much.
     
    Ben g. likes this.
  19. Ben g.

    Ben g. New Member

    Messages:
    7
    Enjoy your receiver. It will bring you many years of listening pleasure.
     
  20. adamp

    adamp New Member

    Messages:
    29
    Location:
    Ottawa, Ontario, Canada
    OK; a bit of screwing around today, but it's sorted out now.

    I replaced the two caps that I had previously removed, no change. I kept poking around, and the caps between the two that I had changed also caused the right channel to cut in and out when poked at, so back to the electronics store, and I bought those ones as well. After installing them, it seemed better but would still drop the right channel when prodded... Then I realized that I was flexing the circuit board slightly by poking at it with a chopstick, so I started looking at solder joints in the area.

    It looks like someone had replaced that STK module at some point, as the solder joints looked a little flaky and not nice and uniform like the other ones in the area. I heated them up and resoldered them all, and it's working properly now.

    On the one hand, I feel that I should have looked around a little better before jumping at the chance to replace four capacitors, but on the other hand, they were kind of bulging and one was leaking, and they cost a grand total of $7.05 (Canadian), so I'll chalk it up to a learning experience.

    At any rate, this thing is working flawlessly now and sounds great. Too bad it's in kinda rough shape cosmetically as I plan to sell it to free up some space. I just figured I'd be doing well to get $75-100 for it locally, so I didn't want to pay a tech $50-75 to fix it... and if I screwed up and cooked a receiver that cost me $10, no harm done.

    Maybe I'll try to find some replacement vinyl woodgrain locally to redo the cabinet with; that should pretty it up a bit and make it easier to sell. I still think I prefer the sound of my 22xx Marantz receivers, but I have a newfound appreciation and respect for Sansui gear, as I had never listened to one before. Especially for a lower end/lower power model (12-15 watts per channel depending on what source you believe), this receiver rocks!

    Thanks for all the help, guys!

    -Adam
     

    Attached Files:

Share This Page