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  #1  
Old 02-23-2012, 02:28 AM
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Montycat Montycat is offline
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Unhappy Picked up a Pioneer SX-450 with the dreaded power switch issue...

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.

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.
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Old 02-23-2012, 03:07 AM
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1973BuickGS 1973BuickGS is online now
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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. 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:

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Old 02-23-2012, 09:29 AM
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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:

http://www.audiokarma.org/forums/sho...d.php?t=415741

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.
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Old 02-23-2012, 10:01 AM
quaddriver quaddriver is offline
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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.
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Old 02-23-2012, 10:30 AM
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I guess I owe you a coffee for sending this headache your way.... Good luck with the fix.
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Old 02-23-2012, 11:19 AM
qsaudio qsaudio is offline
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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.
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Old 02-23-2012, 01:52 PM
quaddriver quaddriver is offline
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Quote:
Originally Posted by audiojones View Post
Wasn't me, but whenever I come across one of the many brands of receivers that use that same crappy Alps power switch I always clean what's left of the contacts and then install a RIB relay to handle the load. Done a bunch (most recently the 4070s and the 1515) and never had one fail or come back, and the RIBs have pre-wired leads so it's a good, fast and permanent solution. What's your fix?
lookit this thread: http://www.audiokarma.org/forums/sho...17&postcount=1

crap, wronggggg:
http://www.audiokarma.org/forums/att...8&d=1175137712
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Old 02-23-2012, 02:47 PM
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Quote:
Originally Posted by quaddriver View Post
That looks better than some of the other threads I've seen on the Pioneer specific fix. I think that is the design I have but I'll look more closely tonight.

Thanks!
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Old 05-21-2012, 11:18 AM
Adirondack Adirondack is offline
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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
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  #10  
Old 05-22-2012, 10:01 PM
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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:

http://www.audiokarma.org/forums/sho...d.php?t=173215

I'd consider the relay as well.
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Old 12-11-2012, 05:23 PM
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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.
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Old 12-11-2012, 11:27 PM
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go to the pioneer forum there is lots of info there about it
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Old 12-12-2012, 01:55 AM
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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.
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Old 12-12-2012, 09:27 PM
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Watthour Watthour is offline
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Check this before you perform any unrecoverable alterations:

http://www.audiokarma.org/forums/sho...d.php?t=372256

The 450 uses a similar arrangement, but probably has a different switch such as this:

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Old 12-13-2012, 05:41 AM
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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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