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STK-0050 replacement for SX-780 and others

Discussion in 'Pioneer Audio' started by rcs16, Jun 18, 2016.

  1. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    lets just ignore that one thread. You should familiarize your self with the units construction, identify where the line voltage is present and avoid that area. Follow the good practices as suggested.
     
    merlynski likes this.

     

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  2. Watthour

    Watthour Electron Rancher - JS3600

  3. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,101
    Location:
    uk.. the middle bit
  4. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    18,777
    Location:
    Cleveland, Ohio
    I encourage anyone who has an interest to learn Electronics theory in order to learn how to properly troubleshoot equipment. You really have to understand the circuits and how they work in order to figure out why they are not working. A great place to start is the book, "The Art Of Electronics" by Horowitz. It is very easy to read and gives your really everything you need to know. Best of all you can download it free here: https://archive.org/details/TheArtOfElectronics-2ndEdition
     
  5. Watthour

    Watthour Electron Rancher - JS3600

    Green fortune cookies are generally to be avoided, but if you really want one...
     
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  6. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,101
    Location:
    uk.. the middle bit
    not the cookie the power pack .. no mention of how to choose black or green in the ad . i dont like the pins on the green one as it happens . :D but hey . :idea:
     

     

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  7. Watthour

    Watthour Electron Rancher - JS3600

    I'll give you this - Your sense of humor is fully intact.
     
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  8. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,101
    Location:
    uk.. the middle bit
    i heard folk are making better than original ones that can be fixed easily in a very very rare case it destructs itself .
    i did once fix an original one . luckily it was a broken wire . never seen one since .
     
    Last edited: Apr 24, 2018
  9. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    I would like to know more about these cases of destruction.
     
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  10. depaj

    depaj Member

    Messages:
    56
    Location:
    lyon, France
    Hi!

    Just a little update to say these modules work absolutely perfectly in a Technics su-v4 I repaired !! it also allows you to keep all the tone controls in the feedback loop. It's very stable, easy to mount (just had to drill 4 extra holes and remove some of the synchro bias circuitry included in the stk's) and sounds (in my opinion) a little better then the original ST8050 that were used (they fail very often and are heavily counter fitted). Thank you RCS16 for your help.
    DSC_9916.jpg DSC_9934.jpg DSC_9945.jpg
     
  11. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    Wonderful, well done.
    You reported a hum problem, has it been solved?
     

     

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  12. depaj

    depaj Member

    Messages:
    56
    Location:
    lyon, France
    Yes the hum problem was due to the MX50 module I used before stumbling onto this thread. The amp is as silent as can be even with volume cranked way up (that is without signal of course :biggrin:)
    .
     
  13. Bassblaster

    Bassblaster Super Member

    Messages:
    2,093
    Location:
    Cambridge, Ohio
    After reading the last 5 pages since i forgot about this thread because AK stopped sending me alerts for it, i think it may be a good idea to make a bigger version for the 100W+ STK packs. such as the 0100. maybe have it run 2 pairs of TO-264 outputs for 4 Ohm capability. OR, keep this current design, but make it have the output on the top opposed to the sides, as some units dont have the space for the extra width.
    im by no means an expert, but if i had a schematic i could start on a PCB.
     
  14. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    Probably should start a new thread as well. Reserve this thread just for the STK-0050 and its applications.
    When I was designing this stk, I initially had the devices on top but we found that it was better to have them on the sides for the SX-780.
    You have to have a target device to design against, as each have there own set on mechanical/electrical issues to address as part of the design process.
     
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  15. Late70sBias

    Late70sBias New Member

    Messages:
    13
    I saw where someone asked the question if this design would work for the Pioneer SX580 which has a STK0029 module in it.
    I didn't see a clear answer or maybe I just missed it. I have an SX580 with both channels dead and I have found original replacement modules but they are expensive.
    Will this electrical design work for the STK0029 excluding the mechanicals?
     
  16. Late70sBias

    Late70sBias New Member

    Messages:
    13
    This is my first attempt at sorting a vintage receiver, and this is a beginner set so I'm not to worried about completely killing it.
    My concern is killing a good set of expensive factory STK0029 that someone who has a pristine until would love to have.
     

     

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  17. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    I think the stk-0050 module I designed can be made to work in a sx-580. You will need the 0.22 ohm emitter resistors, same as what the guy did in thread #410 above. bias has to be tested to see if you get the ~35mA.
    Always test on the DBT to be safe.
    if this works it is way better than the originals. You can use 150W output stage bjts, they are a bit cheaper.
    It is summer, lawn mower broke today, need a weld, I would like to simulate the sx-580 design ... but I have no time right now. Another day perhaps.
     
  18. Late70sBias

    Late70sBias New Member

    Messages:
    13
    Thanks for your efforts on this project and the advice, I will go ahead and attempt this and hopefully learn something.
    Smoke proceeds enlightenment!
     
  19. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    This fusible 5 amp resistor protecting the board components located between pins 2 and 5 of the unregulated. Mark started the discussion but other aspects are missing. Is there any more discussion? I can't find where the Mouser 576-0251005.MXL part was mentioned. I completely understand the purpose but want to convey it to the sellers with questions. Which I can but want a link to reference.

    There is no over current protection the SX-780 power amp design. Mark was discussing adding it as was done in the SX-880. I said it would mean adding the ckts to the existing pcb and doing some mods/add wires to the mother board. Too much BS for most to bother with, imo.
    The optional axial fuse idea I thought was a cheap way to add some protection in a shorted output condition. It is hoped the bjts survive long enough for the fuses to blow.
    Maybe Pioneer should have done the same and saved many the bother of blown modules.
    Fuses can be a nuisance in some cases. Maybe a 5A fuse is too low for the devices we are using, if you are blasting it? If one fuse blows and the other is still intact, there will be an immediate large DC offset, relay will open, but speakers could get damaged in the process. A blown bjt would mean the same too. The o/p bjts are almost the same cost as the fuse :)
    There are cheaper fuse options
    https://www.mouser.ca/Circuit-Prote...Through-Hole/_/N-ba8hh?P=1z0x8gg&Ns=Pricing|0

    YMMV
     
    Last edited: Jun 6, 2018
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  20. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

    Messages:
    10
    Location:
    Mechanicsville, Virginia
    Thanks dr! Have been looking for something like this for a while. And the price is right!
     

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