Pioneer SX-450 does not power on power but switched outlet works

Discussion in 'Pioneer Audio' started by Lance23, Sep 7, 2017.

  1. Lance23

    Lance23 New Member

    Messages:
    3
    Pioneer SX-450 does not power on power but switched outlet works, can someone point me in the right direction to troubleshoot

    thanks
    Al
     
  2. macyjrm

    macyjrm AK Subscriber Subscriber

    Messages:
    1,075
    Location:
    Mississippi
    The power switches on this model are trouble prone. They can be repaired but doing so requires some patience. Using google, do a search for SX 450 power switch. Follow the links that take you back to Audiokarma. There are several well documented threads that demonstrate various repair methods. The switch is basically like "points" in vintage auto ignition systems. The points build up corrosion over time that can be easily remedied by fine sandpaper or finger nail file. The challenge is getting to the switch. I was able to repair mine without removing it from the chassis but it took most of a Sunday afternoon. No rocket science required, just patience.
     
  3. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
    4,243
    Location:
    Las Vegas Nevada
    Good wisdom from "macyjim"
    Some added embellishment:
    Check the main fuse for condition and proper rating.
    Then bypass the main power switch using a safe jumper.
    Build a DBT (Dim Bulb Tester) with a switch, if you don't have one.
    Plug the set into the DBT using it as a temporary switch.
    This will confirm the poor power switch condition(?) and check the set for any shorts before plugging it in to full house power.
     
    Last edited: Sep 8, 2017
  4. Lance23

    Lance23 New Member

    Messages:
    3
  5. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    169
    Location:
    High Plains, Eastern Colorado
    If I understand correctly the 'switched outlet' powers on and off with the power switch, but the Receiver stays dark and silent? If so the switch is not the problem.
    Look at the schematic, there is a 3 amp fuse (FU6) to the transformer primary that may be blown. It does not affect the switched outlet but will interrupt the power to the Receiver's power supplies. Check the fuse with an ohmmeter (unplug the power cord first), 0 ohms is good. If it is open (bad) something deeper inside may have caused it to blow. If you have a DBT replace the fuse, plug amp into DBT and try turning it on. If the DBT bulb comes on bright for a moment then goes dim try again without the DBT.. If the DBT bulb stays bright the problem is deeper inside. You can build a Dim Bulb Tester for cheap, instructions and explanation are on AK. Zeb is on the right track . . .
     
  6. Lance23

    Lance23 New Member

    Messages:
    3
    ok thanks for the replies, will do some more testing and report back...


    thanks
    Al
     
  7. phreshboy

    phreshboy New Member

    Messages:
    5
    Location:
    Columbus, Ohio
    I have the same problem. I have continuity between the switch when on and none when off, I also have switchable current to switchable outlet. However there is no power on the fuses, and jumping the power switch does nothing. I have checked and re-checked the fuses, all test good. There simply is no power getting to the unit. The power cord tests fine and I checked the rectifier diodes as well, all test good. I am fit to be tied here as everything from the power cord to the fuses to the switch seem fine. There is an odd piece of gear bolted to the chassis that I do not know it’s function. Simply a terminal strip like thing with a large disc cap between two of the four posts. Maybe a type of surge protector?
    I have learned a lot from this group and seldom post anything so thanks in advance for any help here. Thank you.
     
  8. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    169
    Location:
    High Plains, Eastern Colorado
    With Receiver UNPLUGGED from power: find the brown and white wires from the power transformer, follow them to where they are connected. Brown connects to the power cord and one side of the switched and unswitched sockets. White connects to pin 4 of the AWK-060 circuit board. Measure resistance between those two points to check continuity of power transformer primary winding. I don't have one to check myself but I expect somewhere between 75 ohms and 120 ohms. Report your measurement
     
  9. phreshboy

    phreshboy New Member

    Messages:
    5
    Location:
    Columbus, Ohio
    Thank you for the reply. If I have measured the right points then I am getting an open reading. I have attached a photo of where the brown and white wire terminate. Thanks again.
     

    Attached Files:

  10. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    169
    Location:
    High Plains, Eastern Colorado
    Good photo, that round device in the heat shrink is a capacitor. The open reading tells me the transformer primary winding has failed open. You will need to replace it to (first step) get this unit working again. :( Sometimes transformers have internal thermal fuses that open if they overheat. These fuses are difficult or impossible to replace. The schematic does not show one for this transformer, and low power amps are less likely to have them, from what I have seen. Good luck!
     
  11. phreshboy

    phreshboy New Member

    Messages:
    5
    Location:
    Columbus, Ohio
    Thank you for the help.
     
  12. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    169
    Location:
    High Plains, Eastern Colorado
    You're welcome! If you become a Subscriber you can post a 'Part Wanted' in Bartertown Parts and some other AKer may have a transformer for a reasonable price.
     

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