Pioneer Spec 1 Pre-Amp Sound Issue

Discussion in 'Pioneer Audio' started by xXColdShotXx, May 13, 2018.

  1. xXColdShotXx

    xXColdShotXx Active Member

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    I am storing my uncle's spec 1 and spec 2 components. I decided to hook up the spec 1 since he said something was wrong with it. I wanted to see what it sounded like. The left channel works pretty good, but the right channel barely plays and fades out if you mess with the bass, treble or volume. I used it as a pre-amp only hooked to my yamaha mx-800/u. The volume, pots and switches need cleaning. The spec 2 supposedly works fine, haven't hooked it up yet. Anyone have a guess what might be going on with the right channel of the spec 1? Thanks in advance.
     

     

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  2. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    I finish restoring one last week. It had different issues.
    What does it do with the tone defeat?
     
  3. xXColdShotXx

    xXColdShotXx Active Member

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    When I turn tone switch off it just cuts off the bass and treble, still has a little bit of audio coming through.
     
    Last edited: May 13, 2018
  4. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Very hard to say at this point.
    A thorough Deoxit treatment is in order before any real troubleshooting is done.
    Barring that statement, every Spec 1 I've done has had a different issue.
    Basically, it could be anything.
    There's several problematic transistors located on each board and should be replaced with new equivalents.
    The input board has been a source of issues on a few with one channel not working but this is only a guess. It's fairly easy to check for the signal through the input board.
     
  5. xXColdShotXx

    xXColdShotXx Active Member

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    Thanks for the info. I have some deoxit. I'll ask my uncle if it'd be ok to clean the pots and switches first. Could a person loosen the volume screws enough to get deoxit in there without taking a chance on messing anything inside up?
     
  6. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Tracing the signal through the pre is the best approach. If it appears to be the volume control, deal with it at that point. No need to open a can of worms.
    Deox the controls first, then trace the signal through the set. Find where it gets lost. Repair and consider replacing the old transistors.
     

     

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  7. xXColdShotXx

    xXColdShotXx Active Member

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    I cleaned the spec 1 controls with deoxit and they work a lot better. the right channel doesn't cut out anymore and plays, but doesn't have the bassy thump like the left channel.

    I checked all the tape and aux inputs, they all have the same music output.
     
    Last edited: May 14, 2018
  8. xXColdShotXx

    xXColdShotXx Active Member

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    Does anyone have an updated caps, diodes and transistors list for the spec 1 pre-out board(s)?
     
  9. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Search “Spec 1 restoration Audiokarma”
     
  10. xXColdShotXx

    xXColdShotXx Active Member

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    Just hooked the spec 2 up and let it play for around 10 minutes, then all the sudden I hear a small pop and smell something get hot, then I noticed the right meter was almost on 500 and the protection light was on. I had a yamaha cx-600/u pre-amp hooked up to it and it was playing just fine on both channels until that happened.
     
  11. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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  12. xXColdShotXx

    xXColdShotXx Active Member

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    Thanks, Zebulon1.
     
  13. xXColdShotXx

    xXColdShotXx Active Member

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    Hey Zebulon, would you happen to know an alternative to 647-UKL1H010KDDANA? On mouser it says non-stocked. It's the only one on the spec 1 bom list that way. Thanks in advance.
     
  14. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    505-MKS2B041001C00JS - Film
    647-UKL1H010MDDANA - Aluminum Electrolytic
     
  15. xXColdShotXx

    xXColdShotXx Active Member

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    Thanks, Zebulon. Is there a resistor and diode spec 1 list around? I also need a spec 1 power light bulb replacement # if there are any.
     
    Last edited: May 15, 2018
  16. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    I saw a post one time on the lamp. An LED I believe. See the scat, it may lend a clue to the voltage requirements.
     

     

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  17. xXColdShotXx

    xXColdShotXx Active Member

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    Should I worry about diodes and resistors? or wait and see how the caps and transistors goes?
     
    Last edited: May 15, 2018
  18. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    You can check for service the diodes and resistors. No need for a preemptive order.
    Are you capable of this level of repair? Tooling, industry knowledge?
     
  19. xXColdShotXx

    xXColdShotXx Active Member

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    I have changed a few in my sx-1250, but it's been a while since then. Would a bad cap or transistor cause the spec 2 to go into protection mode with the right meter almost maxing out when I turn it on now?
     
  20. xXColdShotXx

    xXColdShotXx Active Member

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    I learn as I go, and I learn fast...most of the time.
     

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