STK-0050 replacement for SX-780 and others

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

  1. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    The Fisher stuff is really nice equipment. I've repaired several of the RS-2010's and found them a well thought out and sounding set.
    They use the STK-0105 modules and run a 100 watts. Many have the smaller modules installed because the big, high power 0105's blew out and couldn't be found. Why? Because they were junk. Underrated for the job.
    If a module could be made, it would be a monster in it self and the sets it would go in would be limited for room.
    A stack-able arrangement with two boards? Starting to get kooky.
     

     

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  2. rcs16

    rcs16 Super Member

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    Okay, I see what it is all about. mechanically there seems like lots of room to work with. Obviously, without me simulating the design, I can only speculate that I think the stk-0050(with 200W devices) could work. Something with this voltage really should have 2 o/p pairs/ch. This is where I think the originals failed.There is the possibility of just adding another o/p device in parallel (with fly wires/proto pcb/emitter,base R's) with what is on the existing pcb. more of a mechanical challenge than an electrical one.
    The design looks well done from a glance.
    Send me a broken BA-6000, for my efforts and I'll design a proper module for it and all your sets :)
     
  3. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Bam !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" :beerchug:
    Now were talking.
    Although there isn't as many of the bigger sets.
     
  4. fisherphile

    fisherphile New Member

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    I couldn't possibly be more thrilled and excited about this, I'll dig out one of them, im pretty sure I left one of them "AS IS" after it burnt up, some of the others I "tried" to fix and are probably worse or missing pieces. When this failed it took out some small resistors on the PC aswell, They all burn in the same spot based on every bit of research ive found online yet no one has had much explanation. It will be fun to hear from you what you see in there. My tech is good but hes secretive he wont tell you his tricks ;/
     
  5. kcsoundguy

    kcsoundguy New Member

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    0B36A88C-02DA-4955-A407-38D2DA840F47.jpeg

    Here they are! Biased them to 15mV and realigned dc offset. She’s sounding fantastic! :banana:
     
  6. rcs16

    rcs16 Super Member

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    I thought about this Fisher BA-6000 app a bit more. Without going through the bother of designing a new module, I think that you can get away with just drilling 2 new holes in the existing AL plate, with the holes centered for the STK-0100, which are 70mm apart.
    These holes are to be centered between the devices mounted to the AL plate.
    You can chop away some of the pcb between the edge and the holes to allow screw access. that is if it interferes with you accessing the screw to attach the STK Al plate to the existing heatsink.
    If you ask Zeb nicely, he might be able to do this for you if order his plate/pcb kit.

    You also have the option of using the slightly higher powered 230W MJL4281A/MJL4302A devices
     
  7. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    You ran this match up in Spice and it seems to work?
    I wish I had a big Fisher to try it in.
    I can mod a pair of heatsinks for the 70mm attachments. The big Fishers have an external heatsink which allows access to the back. I could thread the new holes to make the mounting easier.
     
  8. rcs16

    rcs16 Super Member

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    The MJL4281A/MJL4302A devices are the same family, similar op, in the sim's. I just sim'd the CA-8000 design, same.
    I have not spiced up the BA-6000 design with the STK module, I'll get around to it eventually.

    That is great that you can check out adding the 70mm holes, what ever is easier, options are good too.
     
  9. fisherphile

    fisherphile New Member

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    luc3l10.jpg stk.jpg
    Here's a look inside, fortunately although I am learning electronics I am a skilled machine shop leader in a tool and die shop so getting the modules in is no issue. Also, I can still send you my Bad unit if you want to test your modules in it yourself in the name of science.
     

     

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  10. rcs16

    rcs16 Super Member

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    Thx for the pics, I looked at them from the net too :)
    Since you are mechanically inclined, I think that we should be able to talk/teach you through using the existing modules. Others in your position have done so. All you need is a DMM/soldering -iron/tools as a minimum. You can make up your own plates, if you want or get the ones from eBay, if you make your own plates, you can order your own pcb's and parts.
    I asked Zeb if he could add the 2 extra holes for 70mm centers. but we need to test out on other 100W units such as yours.
    No need to send me a unit, the $ could be better spent for you buying parts. If the existing modules do not do the job, then we can look at sending me a unit to design a new module for.
    Okay with that?
     
  11. fisherphile

    fisherphile New Member

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    Okay, but before I do that I'm going to Photo my actual board so you can see the damage and tell me if it at least seems typical of a chip failure. For all I know something else is going on.
     
  12. rcs16

    rcs16 Super Member

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    yeah, that is a problem, basically means going over all the comps, checking them out for spec, inspecting traces for opens. It is a fair bit of work. I do not mean to make it sound easy, as it can get involved if there is collateral damage.
     
  13. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    The probability is, the driver board is good. Just needs a good looking over. Use the resistor trick and make sure the amp behaves.
     
  14. fisherphile

    fisherphile New Member

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    a few years ago I actually spent months on one of them. rebuilt the board and inspected everything i could with my meter. got new chips (not china) and when rebuilt i fired it up and it blew up again in the same place. that's when i realized i don't know enough yet to repair such an involved piece of equipment and i boxed it up. I'm seriously considering just taking it in and having it brought back to life then just replacing the chips with the modules when i get it home. The two amps i have in use right now also need a refresh
     
  15. rcs16

    rcs16 Super Member

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    yeah, been there ;-) but since figured that one needs to build a DBT and how to better troubleshoot, rebuild amps, sub parts. Having a schematics helps so much, in the old days, no net, getting a service manual was expensive and a royal PITA. Having to repair an amp with no schematic is a talent and a challenge.

    If you are not up to it, Zeb was thinking about buying a 100W Fisher on eBay, to try out the modules in. Maybe it would be cheaper to send your BA-6000 to him. I am in Canada, it is a lot more expensive to ship here. See if you guys can work something out. I can help when needed. I can start and simulate the design at least as a sanity check.

    I'am pretty sure the module will work in a BA-6000, the VAS bias current is about the same as the other Fisher gear. This determines the components in the Vbe multiplier, which sets the o/p stage bias.
    I do suggest to use the slightly higher powered 230W MJL4281A/MJL4302A devices, if they can be made to fit, they may interfere with the 70mm centered holes for mounting the plate.
     
    fisherphile and zebulon1 like this.
  16. fisherphile

    fisherphile New Member

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    Sound good to me! I'll get it boxed up!
     
  17. rcs16

    rcs16 Super Member

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    Zeb is in agreement? if so great and good luck guys.
    Where are you located fisherphile?
     

     

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  18. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Conversation started.
    Fisherphile: See your in box
     
  19. fisherphile

    fisherphile New Member

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    About 8 hours south of you in the Detroit area
     
  20. rcs16

    rcs16 Super Member

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    Detroit, Mi to Georgina,Ont = 454 km - 4 hours 23 mins by car, 2:15 if we meet in the middle, London area, all # 401
     

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