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Looking for some help with my sx 1050

Discussion in 'Pioneer Audio' started by Stinkpot75, Jul 24, 2018.

  1. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    After replacing a bunch of capacitors I was checking DC offset on post 4 (like the 10th time) when my clip slipped and touched post 3 too. I thought it just blew the 10 amp fuse so I replaced it. Now I have a fried R1 on the surge suppressor 098 board. I found a replacement for that 3.3 ohm R1, but what else should I look at? What else might I have damaged?

    Thanks
     

     

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  2. Watthour

    Watthour Electron Rancher - JS3600

    Welcome Aboard. !

    The AWX-098 soft-start board may have saved a lot of other damage to the unit by sacrificing the resistor when the unit was powered on after the "incident" with the meter probe.

    That slip temporarily applied the -60V bus (rail) voltage to the amp output. It would be prudent to check the main amp board left channel emitter resistors R49 through R67, and the driver and output transistors Q13 through Q29. This should all be done with power off.

    It would also be prudent to connect the receiver through a DBT to limit line current when powering the unit back on for the first time.
     
    avionic likes this.
  3. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    549
    Location:
    High Plains, Eastern Colorado
    The thermal fuse in series with R1 on the soft start board should have opened and protected R1 when it got hot, long before it destroyed R1. Unless somebody bypassed it, like on this one. soft-start-1050.JPG soft-start-1050-2.JPG
     
  4. Watthour

    Watthour Electron Rancher - JS3600

    Self-inflicted wounds are the worst. That NTE fuse is about four bucks. The resistor is probably $50. I just don't understand the logic of some people sometimes.
     
    merlynski likes this.
  5. embrown057

    embrown057 Active Member

    Messages:
    204
    Location:
    Apollo Beach,FL
    If you need that resistor let me know, I have a few extra.
     
  6. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    Thanks everyone. The thermal fuse is open and the resistor still measures 3.7 ohm. The coated wire tied around the two parts is what smoked. I've been looking for the right micro-temp and it seems hard to find a 109C 10A, most I see are 15A 250V. Since this is a thermal fuse I wasn't comfortable with just getting something close. What's a good replacement? They look fine, but I still gotta get in there and measure the parts Watthour suggested. Can the transistors be tested on the board?
     

     

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  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Exact replacement.. 109°C = 228°F 10Amp
    https://www.alliedelec.com/selco-swtc-228-3535/70098743/
     
    Last edited: Jul 29, 2018
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  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,701
    Location:
    Fort Dodge, Iowa
    Not reliably..
     
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,701
    Location:
    Fort Dodge, Iowa
    When resoldering the new thermal fuse onto the board. Clip some kind of heatsink on the lead your soldering. Or solder very quickly . To much solder heat could destroy it.
     
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  10. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    Thanks avionic, I was wondering about that... just ordered a few of those fuses.
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
    Fort Dodge, Iowa
    BTW welcome aboard stinky..:biggrin:
     

     

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  12. slow_jazz

    slow_jazz AK Subscriber Subscriber

    Messages:
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    Good luck.
     
  13. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Las Vegas Nevada
    merlynski likes this.
  14. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    549
    Location:
    High Plains, Eastern Colorado
  15. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    222
    Location:
    Mamou, Louisiana
    After you replace the thermal fuse, before checking all those components in the amp, save yourself some time and power up the 1050 for the first time using the DBT. I would use a 60 or 75 watt bulb. The DBT will pretty much tell you if anything is shorted in the amp or power supply. If the bulb goes dim, you are probably good to go. But while powered up with the DBT, check the DC offset and bias. If all is good, you should get audio out to the speakers with the volume control set at low volume, around 9 O'Clock position but no higher.
     
    Last edited: Aug 10, 2018
  16. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    Thanks again for the advice y'all. I'm gonna pull those parts and test them soon. Will have to build a DBT before any power too.
     

     

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  17. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    Without removing anything I went ahead and measured R49 through R67 and everything looked good except R51, which was 6k not 18k.
     
  18. Stinkpot75

    Stinkpot75 New Member

    Messages:
    18
    Finally got around to at least checking the left side output transistors. Looks like one bad 539C and one bad 287C. What's the advice here? Find two old ones, or replace all with new equivalents?
     
  19. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    549
    Location:
    High Plains, Eastern Colorado
    My opinion: replace all with new equivalents. New insulators, fresh heatsink paste.
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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