STK-0050 replacement for SX-780 and others

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

  1. Awesomeaudio

    Awesomeaudio AK Subscriber Subscriber

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    1100 pages too !! Wow.
    That'll keep you busy for a while :D
     

     

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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Yeah but 40% are PICTURES and they don't count.....unless you happen to be an ex-Torpedoman, Boatswain's Mate, or a Bloody MARINE!:D:D:D

    ( this Hospital Corpsman is going DEEP below the Layer and Silent Running!)
     
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  3. rcs16

    rcs16 Super Member

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    3,808
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    Thanks dr! Have been looking for something like this for a while. And the price is right!

    I went through it, it covers a lot,nice addition to the library. basically what I learnt in college in the late 70-80's. Still are making 7400/4000 series logic, cpu's have come a long way. all good info to know, if it applies to what you are doing.
    As far as audio amplifier design books, go to Bob Cordell's new book, pay the $, it is worth every $, if you are serious about understanding this topic. it will be out soon, that and ltspice simulator, the defacto standard these days for linear design.

    That is how I did this STK-0050 design, ltspice and orcad. I have never made one for myself, all virtual, it is cool and rewarding to be able to do it and share it with the world. :)
    Cheers to Zeb for stepping up and making them available to everyone.
     
    Last edited: Jun 7, 2018
  4. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Rick, attached is an SX-580 sim for STK-0050 from LTSpiceXVII. It was adapted from another of your sims. The output is way overdriven (square wave) but produces no errors or complaints from LTSpice when run. If you get the inclination to run it . . . :)
    I put the tone controls' components in the schematic because they are integrated into the power amp stage negative feedback loop, but may not be necessary to the simulation. I used two equal resistors to emulate the (centered) tone control pots.
    AK would not let me upload the .asc file, so I zipped it.
    Enjoy, and thanks for your work!

    EDIT: P.S. Please verify I subbed the correct transistors . . .
     

    Attached Files:

    Last edited: Jun 7, 2018
  5. rcs16

    rcs16 Super Member

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    3,808
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    That is great Merlyn.
    I changed the level for Vin1 to 0.17 which is just below clipping. VR3 to around 110 ohms. So it works fine imo.
     
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  6. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Rick had sent a ItSpice sim to help me detail the larger watt version. I’m going to make time to learn this tool.
     
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  7. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Made those changes in my sim and got the same result :thumbsup:
     
  8. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    FWIW, the SX-680 PA connection to its STK is identical to the SX-580's. Somebody, in a previous post asked if the STK-0050 upgrade kit could be used there.
     
    Last edited: Jun 28, 2018
  9. Kingbleu

    Kingbleu Active Member

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    147
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    Southern California
    About to order four kits from Zeb through the ebay. I have two SX-780's in the garage. One working and one dead. Looking forward to restoring them both. Thanks rcs16, HBrown, Zebulon1 and all the others.
     
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  10. Arthur Smith

    Arthur Smith Well-Known Member

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    835
    Is there an easy way to test an STK-0050 out of circuit?
     
  11. rcs16

    rcs16 Super Member

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    One usually uses an ohmmeter, sometimes you have to isolate a component from the others to make a proper measurement or factor in the ckt arrangement (if know it) to make sense of your readings.
    A test jig will work too but you still have to isolate the fault if want to repair it.
    The ckt has floating emitters at the o/p, it is a 2 emitter follower design, so the two base-emitters are in series for 2 Si diode V drops, >= 0.6V * 2
    The Vbe mutiplier can be ohmed out. Always can ohm out a good one vs a dead one.
     

     

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  12. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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  13. kdris10

    kdris10 Member

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    Is there a way to set the idle current with these new modules?
     
  14. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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  15. Watthour

    Watthour Electron Rancher - JS3600

  16. kdris10

    kdris10 Member

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  17. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    It depends on the set your installing them on but 7mV across the one emitter resistor will get you a nominal, working setting.
     
  18. oldgearhog

    oldgearhog Member

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    Is there a list compiled of which modules this will work as a replacement for? I have a Technics SA-300 that uses an STK-0039. From what I've read in this thread, it sounds like it would be a suitable replacement. Would there be any component changes? The receiver is spec'ed at 35 wpc.
     
  19. rcs16

    rcs16 Super Member

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    3,808
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    I have not compiled a list myself. Basically it consists of the intended Pioneer SX-780, a few Fisher models and a Technics ST-SA5ES so far to my knowledge.
    As for any design, the mechanics have to be verified for fit and form.
    Always a good idea to post a pic(s) showing how the original is mounted in your unit for us to evaluate.
    Electrically I think it will work.
     
  20. punchback

    punchback AK Subscriber Subscriber

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    I will be building a couple of the modules. Regarding fusing of the modules. The note in the Mouser BOM is to replace the links fo pins 2 and 9 with a fuse. Just so I'm clear, that would be the wires I colored red in the clip below?? I bought a few of the fuses in the BOM but would the blade style plastic fuses, that you typically see in cars, work just the same? If so I could used the fuse holder shown below so in the event of a blown fuse it would be easy to replace. Assuming there's not a catastrophic failure to figure out.

    upload_2018-7-20_13-22-53.png upload_2018-7-20_13-26-30.png
     

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