Picked up a Pioneer SX-450 with the dreaded power switch issue...

Discussion in 'Solid State' started by Montycat, Feb 23, 2012.

  1. Montycat

    Montycat AK Subscriber Subscriber

    The cheap Pioneer SX-450 on the bench right now will probably have me cursing a bit. Pics will follow...

    It's a good thing I only paid $15 for it because it appears, as is stated often in related threads, that the power switch disassembly and cleaning that it seems to need is a PITA. Oh well...I needed something to keep me out of trouble for the next few days. :no:

    I'll also be making some new ends for the case I think as it has some weird chocolate milk brown vinyl veneer on it. Fortunately the rest of the cosmetics are good and it's all there.
  2. 1973BuickGS

    1973BuickGS Impreza wagons for life Subscriber

    Is it stuck on or off? My 750 is stuck on so I just put the plug on a switch. Yes, I am lazy, but it works. :D I'll probably fix it someday...

    As for the vinyl, I redid my 450 (as well as my 750) in cherry vinyl from Dayton. They both came out nice. Here's the 450:

  3. Montycat

    Montycat AK Subscriber Subscriber

    Nice job on your 450. I hope to get mine looking nearly as good.

    However the switch is not stuck either on or off, it has the symptoms of significant contamination/corrosion that is talked about in multiple threads here, this being just one:


    It sort of turns on in that power seems to get to the tuner and the lights will flicker and sometimes even stabilize but no sound comes out. I'll dig in a bit deeper tonight. I didn't know what model or even series it was before going to get it, or I might have had something to look for. It does appear that the problem is fixable though.
  4. quaddriver

    quaddriver 120 What's per channel Subscriber

    I dunno if it was you I talked to, but I published a fix for the 4070 (et al) power switch on AK (with help from EW). Its easy to do and gets rid of the kludge.
  5. whitey

    whitey No time for elitists.... Subscriber

    I guess I owe you a coffee for sending this headache your way.... Good luck with the fix.
  6. qsaudio

    qsaudio Super Member

    The main problem is not breaking or messing up the tuner string, but if it has both sets of contacts, then swap them, it will be just like a brand new switch.
  7. quaddriver

    quaddriver 120 What's per channel Subscriber

    lookit this thread: http://www.audiokarma.org/forums/showpost.php?p=1085717&postcount=1

    crap, wronggggg:
  8. Montycat

    Montycat AK Subscriber Subscriber

  9. Adirondack

    Adirondack New Member

    That switch!

    Hello Andrew & Audio Jones,

    I have an SX-450 with that switch problem. I hate to say it but it's true misery loves company. I'm actually not the only one with this weird problem!

    Flickers on power up, then works fine. I tried first to open the grey box about a 1/4" and spray with deoxit, helped a little. Then I opened the grey box all
    the way (hoping & praying I didn't break that string) I cleaned the contacts
    as much as possible (given the cramped quarters) with emery paper and spayed with CRC. It is much better but still flickers once in a while on power up. There must still be a bit of trash in there, ARRGH! I'll probably go back in there.

    Audio Jones, would you have a supplier for that relay & any chance you could give a novice pointers on the installation? I do OK with the mechanicals, as far as the electrical side let's just say I'm improving.

    Thanks for all the info gentlemen, maybe after this issue is solved I'll be able to trace the problem with the stereo indicator light (no power to the leads)
    at that point it will be100%.

    Thanks again, Dave
  10. Montycat

    Montycat AK Subscriber Subscriber

    I was almost going to trash this SX-450 before checking out some of the threads on it. I got right into the switch box and it is now pretty clean. It stills sputters a bit too though but is much better and stabilizes fast. I did not, but should, clean the speaker contact points too as shown here:


    I'd consider the relay as well.
  11. Montycat

    Montycat AK Subscriber Subscriber

    I finally decided to pull this SX-450 out of the storage bin and think I will get it back to some better semblance of performance. I think I am simply going to bypass the power switch and possibly insert a panel mounted toggle into the microphone jack for the power on/off.

    I wonder if the mike jack has a switching function in it, like a headphone jack might where it shuts off something else when a 1/4" jack is inserted. In other words if I simply detach the mike jack from the PC board will I need to bridge anything there?

    The headphone jack would be better placed as it is right beside the power switch, but I or somebody else is more likely to want to use headphones than a mike.
  12. BranMPioneer

    BranMPioneer Member

    go to the pioneer forum there is lots of info there about it
  13. Montycat

    Montycat AK Subscriber Subscriber

    Oh, I've been all over looking at it from all directions. I did take the switch apart and clean it too but that's only a stopgap as the arcing will continue.

    No I am convinced I will put in another switch. I think I might have just enough room above the headphone jack to drill and mount a pushbutton. I don't think I want to use the mic jack as it does share the Aux input I found from the schematic.
  14. Watthour

    Watthour Electron Rancher - JS3600 Subscriber

  15. Alienz

    Alienz Super Member

    Some 2SA725 transistors were causing start up trouble in my SX450, you could try replacing those before you replace the switch.

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