STK-0050 replacement for SX-780 and others

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

  1. kramden

    kramden Active Member

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    I heard that too back in the day. A friend of mine cracked a few open and looked at the die. :no:
     

     

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  2. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    I've read this thread a few times completely but can't remember if any used this module for a 100 watt amp.
    I get questions from a few buyers through the listing wondering the same thing. Can we use this for any amps rated to 100 watts?
    It looks like a stretch. Looking at the topology. The amps rated at and above 100 watts use a four plus output transistor package.
    Is there a single TO-3P-3 package that could handle this higher rated output?
    I had repaired a few Fisher RS-2010's that used the STK-0105 modules and it's rated to 100 watts. That seems the high power fringe of the STK modules that I'm aware of. :dunno:

    STK-0105.PNG [​IMG] [​IMG]
     
  3. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    The fisher 2010's I repaired, all had the STK 0080 modules and I suspect were replacements for the (More) rare, obsolete STK 0105's.
    The 0080's worked until you you went to far on the volume.
     
  4. Bassblaster

    Bassblaster Super Member

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    From my experience, ive used TO-3P devices is several amps that are 100W and a couple more than 100W i have a receiver with a SINGLE PAIR NJW1302G/NJW3281G (200W) running on +/-55V running full power into a 4 ohm load. i think it clips around the 140W mark at 4 ohm. haven't tested it. thats actually my beater test amp. seems to take it good. been running for a year now i think

    next case that i think is the worst possible design, would be a Sansui i have, that at 8 ohms, is a hair over 120W with again a single pair of 2SC5242/2SA1962 (130W) on +/-70V supplies. runs over 100c most of the time, but has survived the past 5 months or so.

    So i wouldn't worry about 100W of output with these packs. unless the package being used is somithing obviously too small like 80W.
     
    Last edited: Feb 15, 2018
  5. rcs16

    rcs16 Super Member

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    At one time Semelab had more powerful bjt's in a TO-3P,300W but they are obsolete (MG6331) I can see.
    http://canada.newark.com/semelab/mg9411/trans-audio-pnp-230v-18a-to-3p/dp/23T0973
    Using this module in another design you have to check/adj the bias generator, so that that the o/p bjt's are turned on properly. This depends on the constant current from the VAS stage. In the sx-780 it is ~ 3.5mA according to the sch and my sim. Did anyone measure it? :)
    Bassblaster's testing results proves what they can take. Using more o/p pairs is better for number of reasons. But they can handle a lot. MJ2119x can do better for power, the TO-3 can and TO-264 are better packages for Pd.
    I have a F-2980 smoked board (G-7500), Sansui were nuts to only use one pair of 100W bjts. I wish we had NJW1302G/NJW3281G 30+ years ago.
    I wonder if anyone has measured the bias change under idle and full bast? or even thd, i don't have one to try :) I guess I could wire a quick proto, just a few parts.
     
    Last edited: Feb 15, 2018
  6. kcsoundguy

    kcsoundguy New Member

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    I just ordered a kit on ebay for my 780. I have already recapped all the electrolytic caps in the unit. The left channel has a eBay output pack so its questionable how long it will last. I can very slightly hear a difference in clarity between the packs. How will these discrete outputs sound? Will it completely change how the 780 sounds? My 780 is in excellent condition and gets used daily, some of times it gets pushed past half volume. So Id like to keep it going as long as possible. I would also like to say there should be a kit of components available too, I would pay extra if all the components were sourced for me. Thanks to all who put time and effort into this.
     

     

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  7. rcs16

    rcs16 Super Member

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    I doubt it, the only thing I can guarantee is that it will outlast an original STK-0050 and can be repaired for cheap.
    It makes no sense to
    That was never the intent of this project and should be avoided. Mouser or other authorized disti. are the best place to order parts from, you have a guarantee.
    I see today everything is in stock. if you plan on making use of them for future, stock up to avoid the occasional shortages.
     
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  8. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    eBay is the only one making out on this project. Any more processes to the kit would give me an ulcer. :confused:
    The listing sells about two to three kits a week.
     
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  9. rcs16

    rcs16 Super Member

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    Other than supporting eBay, it is a worthy cause :) great little side job for a youth, since paper routes are dead, no pumping gas jobs anymore, you can opt to flipping burgers at McD instead :)
     
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  10. redk9258

    redk9258 Super Member

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    They don't flip anymore. They cook both sides at once. :p
     
  11. elnaldo

    elnaldo Addicted Member

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    Hello. Do you recommend to buy the PCB-heatsink Kit from the ebay link at post #303, or is there other source for them? I was thinking to manufacture them locally (I'm at Buenos Aires) but I think it will be easier to buy the PCB already made.
     

     

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  12. rcs16

    rcs16 Super Member

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    You can order the pcb's as shown in post #1(make your own HS/plate) or buy from the eBay source. Both are the same pcb except with the eBay source you get the Al heatsink/adapter plate and hardware, which is a good deal imo.
    You still have to order the parts yourself or find alternatives locally.
     
  13. kcsoundguy

    kcsoundguy New Member

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    I got my packs all assembled and I forgot the damn 200pf caps, ugh. might try and source those at a local parts house. Do I need to apply thermal paste between the new and existing heat sink?
     
  14. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Paste is recommended.
    I can send you two in an envelope. I use the 220pf's. Anything close will work.
     
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  15. kcsoundguy

    kcsoundguy New Member

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    Sweet. I would need 4 (2 for each pack) id pick up the cost and shipping.
     
  16. kcsoundguy

    kcsoundguy New Member

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    Awesome! I got my modules installed and sounds fantastic. Only my heatsinks don't sit flat to black metal heatsink do to screw that come from the other side of the black heatsink. I'm guessing I need to remove that screw so the module sits flat? I will post some pics soon. I need to do some other work in there too.
     

     

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  17. HBrown

    HBrown Active Member

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    Some units have the backing plate with protruding screws that you are talking about and some do not. They can be removed.
     
  18. fisherphile

    fisherphile New Member

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    If I can remember correctly the 880 has higer voltage so Fisher could slap a "100WPC" sticker on the front. I have to check again its been years but I have a fisher BA6000 with STK0100ii and I believe my rail voltage is closer to 65, is this viable? I am not experienced enough to do this on my own but if we think I can have a favorable outcome I'm going to have these kits professionally made and installed in 4 of those amps :) The plan for years was to make the amplifiers more robust without sacrificing SQ and I'd like more potential. Basically I want what you designed! PS: I have only read half of this thread so far sorry if the question has already been answered
     
  19. rcs16

    rcs16 Super Member

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    These stk-0050 kits are not meant for amps with 65V rails. A STK0100ii is a different design, it is, iirc a EF triple with two sets of o/p pairs. So I say off the cuff, do not bother with this design in a BA6000, as it would not survive if asked to drive loads at full power for long periods of time.
    I'd have to investigate what goes on in a Fisher BA6000. problem is the effort it takes to do a new design, test, mechanics have to be worked out, it is not a simple task. A lot of effort for a one of is a problem.
     
  20. fisherphile

    fisherphile New Member

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    What if I said please extra nicely? :D I will say that I get it. No one likes my Fisher stuff like I do. But it kills me that I have 2 or 3 of these things boxed up that need repair and I'm stuck with gambling on an Ebay power pack. If someone could just show me the way I know I could make this a much better unit. Could you Humor me and take a look at my schematic? I have it on my home computer. Either way, Great job with this. When I saw it today I celebrated it as a breakthrough in the enjoyment and preservation of vintage gear. And it looks better than I ever could have imagined.
     

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