Uh oh. I bought a stinker. SX-3900

Discussion in 'Pioneer Audio' started by Spormo, Apr 7, 2017.

  1. Spormo

    Spormo Professional Novice Subscriber

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    Location:
    East Texas
    I was going around some pawn shops this afternoon and found a pioneer SX-3900 is good cosmetic shape. Everything appeared to work except a few back lights on the source buttons. I could only audition it from FM radio but it sounded like it should. I listened to the other sources and cranked up the volume and could tell they all had a soft static. I figured it worked for now and it looked to be in good shape. I snapped it up for 150. Brought it home, no drops or significant bumps. Plugged her in wired in a speaker and used the aux input and my phone just to make sure everything worked before I wired in everything else. The sound was SO quiet I had to put my ear up to the speaker to hear anything. Played with every knob and switch on the front and nothing affected the volume other than the volume knob and the tape monitor lever. If I put the tape monitor lever to source it gets moderately loud and extremely distorted. I've tried the phono input, aux input, AM and FM radio and They are all extremely quiet. So quiet I can hear the song louder from the actual record than I can from the speaker. I'm really unfamiliar with restoring/repairing vintage receivers/amps etc. If any one could give me some quick things to check or steer me in the right direction I'd appreciate it! I can take pics if necessary, but like I said I don't really know what to look for.
     
  2. Spormo

    Spormo Professional Novice Subscriber

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    Location:
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    Hmm. I feel stupid. Right after posting this I went to mess with it more. Plugged in my phone and turned the tape monitor lever to source (I just found out this should be on source) and now audio plays undistorted and at normal volume. A few minutes ago it was quiet and distorted exactly as it sits now. Maybe I smacked it just the right way or lost my mind and didn't realize I had something hooked up incorrectly?? I have no idea.
     
  3. faber12

    faber12 AK Subscriber Subscriber

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    Probably needs a Deoxit treatment.
     
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  4. Spormo

    Spormo Professional Novice Subscriber

    Messages:
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    Location:
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    Ok so I've listened to a few songs on this thing now. There are some points in some songs where a crackly distortion comes in. I was listening to some classical music and it began to distort when they hammered on some higher notes on a piano and things got loud and a little higher in the frequency range. But after hearing that I played the song again and cranked the volume up and didn't hear the distortion in the same spot. On another song it was just loud vocals and I didn't hear any cracks or pops that stood out the whole way through, it sounded great. Not sure what is up with this thing but I have a feeling it needs some R&R.
     
  5. Killer Fox

    Killer Fox AK Subscriber Subscriber

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    Get some Deoxit. Do a search here and read up a bit. Open her up and spray down controls etc.

    I'm just a noob and have revived several receivers just by internal cleaning.
     
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  6. Spormo

    Spormo Professional Novice Subscriber

    Messages:
    42
    Location:
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    I'll give that a shot. I took the cover off earlier and noticed a fluctuation in volume. I kind of narrowed down the volume fluctuation AND the distortion down to the front right hand corner of the unit by the volume knob. If I apply pressure to the "chassis" here it will get louder or quiet and I can also make it go almost silent like before. Maybe something is loose or dirty on the board near that part of the chassis. I'll look into deoxit, thanks.
     
  7. faber12

    faber12 AK Subscriber Subscriber

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    Maybe bad solder joints as well? That could cause issues that pushing on things can diagnose.
     
  8. Spormo

    Spormo Professional Novice Subscriber

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    Location:
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    Yeah I think so too. I guess I need to prod around on different components and narrow it down.
     
  9. gizzyman47

    gizzyman47 Super Member

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    Nice find! Fun receiver! Hope you get it singing!
     
  10. Skylab

    Skylab Altimeter reading zero Subscriber

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    I have an SX-3900, which I really like. Mine has been recapped and generally restored, but I can tell you for sure, do nothing else until you have treated all the switch mechanisms with deoxit. I would be willing to bet money that's what is causing your issue.
     
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  11. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    http://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/ Go to Guitar Center and get 1ea De-Oxit D-5 and Faderlube F-5. Read the instructions on the link. Apply the D-5 in SHORT SPURTS then exercise the pot a couple times, go on to the next pot and repeat. DO ALL POTS, and SWITCHES. Remember, if it goes round and round, up and down, or in and out, to quote Mark the Fixer, it gets De-Oxit. The D-5 is the cleaner and DeGreaser. The F-5 is a cleaner and lubricant. If any gear has slider pots it gets ONLY FADERLUBE! If you can't find DeOxit handily, CRC QD Electronic Cleaner and CRC 626 Electronics lubricant (Home Depot) is a cheaper alternative but doesn't clean as well.
     
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  12. Spormo

    Spormo Professional Novice Subscriber

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    Location:
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    Me too! It's really a nice looking unit IMO. I'll post some pics to this thread later today.
     
  13. Spormo

    Spormo Professional Novice Subscriber

    Messages:
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    Location:
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    I'll definitely try deoxit d-5 before screwing around with anything or paying out the nose to have it screwed around with. Thanks!
     
  14. onepixel

    onepixel .

    Messages:
    32,366
    When I get old gear, I always clean it first.

    I had a SX-3600, the little brother. I think it's one of the better sounding vintage Pioneers.
     
  15. Djcoolray

    Djcoolray Super Member

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    A rocks throw from JBLM !!!!
    It's a good idea to open up a unit and detoxit the insides using Q-tips before you run it through an audition. Some people have actually burned up units doing that.....
     
  16. Spormo

    Spormo Professional Novice Subscriber

    Messages:
    42
    Location:
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    I'll definitely keep that in mind in the future.

    Here are pics for everyone just 'cus.
     

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  17. Djcoolray

    Djcoolray Super Member

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    Location:
    A rocks throw from JBLM !!!!
    That looks pretty good, but all connections suffer from some sort of corrosion over time. Detoxit eliminates that minimal corrosion which opens up the soundstage of detail and clarity.

    Congrats on finding a great receiver....
     
  18. mquinn25

    mquinn25 New Member

    Messages:
    20
    I love my SX-3900. Picked it up about 3 years ago and decided I need to service it. So, it is apart now and I have some replacement lamps on order. All the switches and pots need a good cleaning. They are very difficult to access though.

    The receiver is a powerhouse for sure!
     
  19. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    I am warning you now; so you don't find out the way I did. The 5 source buttons on the front panel lead through the front panel and the front chassis by way of long extensions which lead to the actual switches in the back of the receiver. When you remove the front panel, the long extensions drop away and are horribly difficult to restore. Take off the top panel first so you can see what I am describing.

    After I tried to restore the extensions to the switches, I somehow ruined my receiver replacing the extensions. If I were you I would try to clean the switches without removing the faceplate or the extensions. I was sorry I did.
     
  20. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    STRAWS!!!!! at the panel end, big enough to go over the extension, small enough to fit through the front chassis hole the extension goes through.
    If I remembered the MM size of the straws, I would have mentioned it.

    Remove the extensions using a small screwdriver blade as a twisting lever at the junction.
     

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