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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:
    4,070
    Location:
    Baldwin, Ontario, Canada
    I would not recommend fuses that are made for cars. The time delay characteristics maybe too long. But it will work, just might not be the optimum solution.
    Yes, install the fuses in the connections to "+" & "-" as you marked in red.

    Good luck
     

     

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  2. petehall347

    petehall347 the brandy coffee man Subscriber

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    voltage rating is to be considered
     
  3. rcs16

    rcs16 Super Member

    Messages:
    4,070
    Location:
    Baldwin, Ontario, Canada
    I think car fuses are 32V so by rights they should not be used for a higher V, as in this case but they will work just not recommended.
     
  4. petehall347

    petehall347 the brandy coffee man Subscriber

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    uk.. the middle bit
    they look out of place anyway
     
  5. punchback

    punchback AK Subscriber Subscriber

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    Hamilton Ohio
    I admit they'd look a little janky, as my daughter might say, but they're under the bottom plate aren't they? Maybe I'll just use the Littelfuse parts since I bought them already. I'm sure you're correct that they'd react much quicker than blade fuse.
     
  6. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

    Messages:
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    Location:
    Mechanicsville, Virginia
    I've seen a few question about using these on a 580 or 680 with a few changes. Anyone had the "cahones" to try it yet? Or should I be the first? :thumbsup:
     

     

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  7. rcs16

    rcs16 Super Member

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    4,070
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    batter up, are you of Greek ancestory?, my dad (parents from Greece) used that one on us as kids.
    Give it a go and I'll support you as best I can. I'd have to look to see if i simulated one of these designs.
     
    mykidsbutler likes this.
  8. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    548
    Location:
    High Plains, Eastern Colorado
    See post #424, SX-580 sim attached, worked fine in sim.
     
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  9. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

    Messages:
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    Mechanicsville, Virginia

    Well, I guess pressure is on! I have all the components, just have not had time to put them together. When I do, I'll be sure to let you know how it went. Thanks all for their support!!
     
    merlynski likes this.
  10. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

    Messages:
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    Location:
    Mechanicsville, Virginia
    Would someone mind walking me through this process? Like where to connect my leads. Have a schematic and have an idea how to, but I just want to be sure since this is my first time doing this. Have build a set and have installed them on my sx-780 and am ready to make my adjustments.
     
  11. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Clip across the emitter resistors on the main board (They measure less than an ohm). If original equipment, they look like long sugar cubes. You only need to measure across one on each amp. DMM set to DC Mill volts.
    Dial the little trimmer on the new module back CCW before applying power.
    The set on your DBT. Check for a dim bulb and then, DC Balance. Power off and connect your meter as above. Check the idle readings (should be .000v and make a adjustment to the idle trimmer looking for a rise in mV readings. If the rise looks good and is predictable, back off the trimmers again and apply full house power resetting the trimmers to 7mV's each.
    Remember, all voltage measured with the set on the DBT will be lower than expected with full house power.
    Once the adjustments are complete and appear to be stable, give the set an ops check.
     
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  12. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

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    Thank you Zeb! I assume after I’m back on house current I would go back and check/ adjust the DC balance again. Installed and adjusted. I now have no more blown fuse, the protection relay clicks in and I have sound. The sound is pretty distorted so also have some other issue. I Dexoit for the third time, no difference. Going to explore other threads to see if I can run down the problem. Thanks again for your help!
     
  13. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    548
    Location:
    High Plains, Eastern Colorado
    Once you are on house power again recheck both channels dc balance and bias. Repeat checks several time until they all settle down. They may interact somewhat.
     
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  14. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    You don’t want to run the set on the DBT.
    Distorted on both channels?
     
  15. mykidsbutler

    mykidsbutler AK Subscriber Subscriber

    Messages:
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    Location:
    Mechanicsville, Virginia
    No. I'm off the DBT. I have distortion evenly on both sides, tone controls work, balance control works. When I get home I'm going to check all my voltages and maybe try to track the distortion down with my oscilloscope, need to learn how to use it anyway, might as well be now.:idea:
     
  16. rcs16

    rcs16 Super Member

    Messages:
    4,070
    Location:
    Baldwin, Ontario, Canada
    use a sine wave source to view the waveforms. input into aux or tape play, select source, scope the input to the power amp at R233,234. then check the amp outputs.
    set scope for AC coupling, ~1ms timebase, trigger off channel 1, ac coupled trigger, triiger at 0V since you are AC coupling the inputs/trigger.
    Check the +/-24V supplies, all the supplies for that matter.
     

     

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  17. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    548
    Location:
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    My SX-780 project is coming along nicely. Had a blown left STK, among other issues. Modules assembled and installed. Just tickled the dragon on dbt (60w). Bulb brightened slightly when bias was set to 34mv on both channels. Cranked it back down. On my modules full clockwise is all the way down, moving counterclockwise brings up bias. DC offset was really jumpy so I pulled the pots, soaked them with D5, then F5, worked them around and reinstalled them. Now they work smooth!
    Tomorrow Full Power. DSCF0722dbt.JPG

    Thank You to rcs16 and hbrown and zebulon1! :biggrin: and to all the great AK people :cool:.

    EDIT: emphasis added
     
    Last edited: Aug 16, 2018
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  18. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    548
    Location:
    High Plains, Eastern Colorado
    Well the Dragon is really messing with my mind this evening. :( Powered up on DBT w 120w bulb, supplies all look good! Power off, switched to full line voltage power, supplies all look good! Back to 120w DBT, set left bias to 34 mv, no problem, power down move dragon claws to right bias test points, power up, still on 120w dbt, set right bias to 34 mv, decided to let it soak a while. A few minutes pass, something starts to smell hot:eek:, then FLASH an 8 inch spark blasts off from the R module :yikes:. Shut down, tested all the silicon on the module, perfect condition:wtf:. Close examination with magnifier finds a small solder blob on the top of the pcb, but not touching any components or traces. :dunno: Cleared blob, powered up on 60w dbt, no problem, powered up again on 120w dbt, no problem, DC offset good. Powered up again on full line voltage, NO problem, offset still good, all power supplies good, relay pulls in normally. Back to 120w dbt, set biases again, NO problem. Power down again, mminimize bias pots, put 5a circuit breaker in place of bulb, powered up again on full line voltage. Tickled the the dragon on left side, stable and normal at 30mv, rose a couple mv over ten minutes. Power down, move dragon claws to R side tps, power up on full line voltage. Set R bias on R side to 31mv. Sitting on full power for 50 minutes now, R bias stable at 32.5 mv. :idea::dunno::crazy:. Power supplies mirrored and stable at +/- 40.0 vdc. Q5 mounting screw head temp stable at 37 deg C on both modules. Guess the SX-780 made its saving throw, 20/d20. (Any old DnD players?) Had enough for tonight, back at it tomorrow. :boring:
     
  19. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Location:
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    Last edited: Aug 15, 2018
  20. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    548
    Location:
    High Plains, Eastern Colorado
    Maybe I was confused :confused:. I was remembering 35 mV (for 80 ma), see rcs16 post #301, page 16; but you are correct about your post. I am measuring across both emitter resistors. I made loops on the wires from the module to the main PCB so i can clip on from the bottom of the amp. (see yellow clips in picture at post #457). I have not tried passing a signal yet, that's for tomorrow.
    Thanks for the reminder:bigok:.
     

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