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Pioneer SX-1250 Keeps blowing speakers right channel, Ideas Help?

Discussion in 'Pioneer Audio' started by electrocuted, Oct 9, 2018.

  1. kevzep

    kevzep Its all about the Music

    Is there a list of what you get? I don't see any resistors, diodes, or transistors in there? Maybe there is but need a list to confirm.
    Part of the issue with these amps is the capacitor degradation, but just as important is the BJT's that also cause issues, such as random popping, sizzling and various other issues.

    I do not agree with the choice of some of the caps.
    The Nichicon FG (Fine Gold) are not what I would choose for power supply applications, especially where they have you fit two radial caps in place of the axial caps, thats just bad workmanship and poor cap choice. There are so many parts of this amp which run so hot, and to slip some 85˚C Audio Grade caps in those places is not a good choice in my opinion.

    They should be supplying Nichicon VX Axial caps in that instance, which are 85˚C rated, but those caps are not in a toasty area.

    Nichicon PW Radial for the rest of the power supply.

    Then depending on personal preference you can use for audio path.
    Nichicon KZ
    Nichicon KT (My preference)
    Nichicon FG
    and for low value you could use WIMA MKS film caps

    Oh, and I only see one relay there too, I always replace the soft start relays as they get a hard time through their life.
    So there should be two relays. I assume the one they supply is the speaker relay.

    This is the path taken here in this forum, and there are countless SX1250 threads to follow along and make good choices from.

    What I would do is when that kit turns up, make a list here of what you've got and we can help you add a few more items to it so you're on the right track to make your SX1250 reliable for years to come.
     
    Bob and merlynski like this.

     

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  2. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
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    Location:
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    **^^^^**. This!
    Edit: I see Kevzep is on this,
    If you want to fix this amp, this is your guy to help you.....
     
  3. electrocuted

    electrocuted New Member

    Messages:
    37
    Location:
    South Florida
    This is the paperwork and parts list I got with box of parts.
    Please feel free to recommend anything else or less than good results with parts I have listed here.
     

    Attached Files:

  4. electrocuted

    electrocuted New Member

    Messages:
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    Location:
    South Florida
    I am not seeing any emitter resistors in this these list, unless I am not reading something right. Take a look.
     
  5. electrocuted

    electrocuted New Member

    Messages:
    37
    Location:
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    Hi I posted the lists of parts he sent, take a look.
     
  6. WE6C

    WE6C Well-Known Member

    Messages:
    516
    Location:
    Colfax, Northern California
    When you take the top "grill" off, do you see the diodes screwed down to the heat sinks?
    Bob
     

     

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  7. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    no mention of brands of parts apart from mpsa92 which i am unsure about in this application . i remember them being low on hfe gain .
     
  8. electrocuted

    electrocuted New Member

    Messages:
    37
    Location:
    South Florida
    I see,
    Nippon Chemi-Con the 4 large caps
    nichicon for most the other black and gold caps
    OMRON relay

    I cant really see the transistor brand name
     
  9. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    on semi according to pdf
     
  10. electrocuted

    electrocuted New Member

    Messages:
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    Location:
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    The Nichicon are rated for 85 C
     
  11. electrocuted

    electrocuted New Member

    Messages:
    37
    Location:
    South Florida
    20181011_192717.jpg 20181011_192725.jpg 20181011_192734.jpg 20181011_192743.jpg 20181011_192751.jpg 20181011_192759.jpg 20181011_192807.jpg 20181011_192818.jpg

    This is the contents of kit, plus the 3 more large caps.
     

     

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  12. kevzep

    kevzep Its all about the Music

    The Nippon Chemicon's they are using for the main caps are okay, I used those.

    Yes, the Nichicon's they have used are all 85˚C caps, which is not the end of the world but would have more durability if they used the higher temp grade and used caps designed for the application. Fine Gold are audio caps for example, not something I use in power supplies although they will still work.

    There are better transistors out there to use than the MPSA, they are an old Motorola transistor which seem to be getting phased out, so many better options now.
    They will be an Onsemi device now as Motorola was bought by Onsemi.

    They have supplied some Nichicon KT Audio caps, and they are good caps, I use them in the signal path
     
  13. electrocuted

    electrocuted New Member

    Messages:
    37
    Location:
    South Florida
    I posted pics of the kit in post #51
     
  14. kevzep

    kevzep Its all about the Music

    Look, its not a total disaster, just not quite what I would use, and as far as the TO220 transistors they have decided on, well, they aren't quite right either.

    I am a bit busy right now, but I'll take a close look and maybe you can just do a small order from mouser and get exactly what you need.
     
  15. electrocuted

    electrocuted New Member

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    Location:
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    So would I be ok if I went ahead with what you see?
     
  16. petehall347

    petehall347 the brandy coffee man Subscriber

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    not sure in this application but i see ksa992 being used mainly instead of mpsa.
     

     

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  17. electrocuted

    electrocuted New Member

    Messages:
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    Location:
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    That sounds really great and many thanks,
    Mike
     
  18. electrocuted

    electrocuted New Member

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    Location:
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    There are 2 horseshoe shaped black what appear to be diodes marked 76A, one ea screwed on top center of each heat sink.
     
  19. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    be very careful with those as wires break close to them and makes it hard to repair them
     
  20. kevzep

    kevzep Its all about the Music

    I will only tell you this once!!! CAUTION CAUTION CAUTION!!!!

    These are STV3 diodes. They are very very difficult to obtain these days as they have not been manufactured for a good many years.
    You must unscrew those, and whatever you do, do NOT grab them and move them around the place, be very very careful, hold them by the legs near the circuit board to move them out of the way, do not bend them by holding the diode, they will break off.
    If you are unlucky enough to have one that is broken and have not noticed, the amplifier will destroy itself, blown output transistors, burned out emitter resistors....you do not want to go there!!

    Extreme caution required!!
     
    merlynski likes this.

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