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Strange SX-1280 Short

Discussion in 'Pioneer Audio' started by ivandezande, Dec 7, 2018 at 10:49 PM.

  1. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    Standard restore, it was working decently before. I'm using a 70W halogen bulb in my DBT. When turned on it's bright as day, and I've checked the entire path and I cannot understand how there would be a short before the soft-start circuit where the relay is for sure not engaging....
    I took out the fuses to the different power supply sections and I felt like maybe it was dimming, but I wasn't trying to leave it on any long to find out.
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  2. Watthour

    Watthour Electron Rancher - JS3600

    How long was the unit left on? If only for a few seconds, the caps may not have charged fully.

    Are there any audible relay clicks while the unit is powered? That's usually 7-10 seconds minimum.

    Also, 70W might just be too small for a 1280. Try bumping to a 100W lamp for a brief period, and possibly 150W.
     
  3. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Halogen bulbs are ok to use in a dbt??
    Looking great otherwise!
     
  4. Watthour

    Watthour Electron Rancher - JS3600

    Halogen incandescents still use a tungsten filament.
     
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  5. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    4,910
    Location:
    Las Vegas Nevada
    Disconnect the big caps and try it.
     
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  6. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    Thank you are for the replies, I think I'm just not giving it enough time as Watthour said as I connected a working 1250 and it took a century to dim even a little.
     

     

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  7. kevzep

    kevzep Its all about the Music Subscriber

    Go higher wattage with the bulb, 100watt maybe even 150....
     
  8. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    I monitor the soft start relay coil voltage, at where the the V drop R connects to the coil, to see what's going on. The longer the S/S relay takes to energize, the longer you have current running thru the big power R and the thermal cutout. I'd say 10s max, it is usually <1s
    The relay coil ckt has a power reduction ecap, that has to charge up as well, thus slows down the v rise rate.
     
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  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,613
    Location:
    Fort Dodge, Iowa
    Is the thermal fuse and ballast resistor still seviceable.
     
  10. rcs16

    rcs16 Super Member

    Messages:
    4,067
    Location:
    Baldwin, Ontario, Canada
    Asking me? if so I say yes
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,613
    Location:
    Fort Dodge, Iowa
    Sorry. No, I wasn't asking. Just using your statement as a reference. If he was waiting a long time for the bulb to dim. And the SS relay hadn't by-passed the ballast resistor. The ballast resistor probably got pretty darn hot.

    Perhaps the dim bulb prevented it from getting hot enough to open the thermal fuse.
     
    Last edited: Dec 9, 2018 at 9:08 PM

     

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  12. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,613
    Location:
    Fort Dodge, Iowa
    A shorted output would cause the SS relay not to " set "..
     
  13. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    21,122
    Location:
    Bensenville,Illinois
    That much of a current draw means:

    1. possible polarity goof on main caps, check with fresh eyes (pictures looked ok, but my factory reference pix didn't show the colors of the wires well enough)
    2. shorted outputs
    3. outputs turned full on HARD: open circuit thermal diode, reversed thermal diode, idle current pot set to maximum resistance.


    The RELAY for soft start runs off of the FU3, FU4 (green brown ct green)
    regulated DC (+/- 68v DC reg) source's power: C5, C6 +/- 88v

    And don't be afraid of the bulb glowing brightly, you can leave it on for say 10 seconds or so without incurring significant damage - the bulb is absorbing the power, so get busy with DMM.

    Oh, and with this big of a unit, use 150 watts of DBT (2 x 75 in parallel).
     
    Last edited: Dec 10, 2018 at 9:22 AM
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  14. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    She powers up ok and the soft start relay energizes, now the speaker relay isn't clicking even with offset at zero...go figure. But that's another problem.
    Thanks everyone!
     
  15. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    4,910
    Location:
    Las Vegas Nevada
    So? What did you find with the issue in post #1??
     
  16. ivandezande

    ivandezande Super Member

    Messages:
    1,775
    Location:
    Twin Cities
    Nothing, I just didn't give it enough time/not a big enough bulb.

    Once off the DBT the protection relay clicked in. Now I just have to tackle some hum issues.
     

     

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