Pioneer SX-450 power switch

Helmut92

New Member
Hi guys,

First of all, sorry for my weak english.
I have a Pioneer SX-450 receiver. Unfortunately there's something wrong with its power switch. When I switch the power on, the lights flicker for a few seconds, and there's some strange noise too, then everything is fine. I've read it's a common problem. The power switch contacts need some cleaning.
I've read a lot of instructions here, how to disassemble the switch and how to clean it. For example this one:
http://www.audiokarma.org/forums/in...sx-450-power-selector-switch-cleaning.173215/

So my question is related with this, and I would like to get some help from those who already disassembled the little grey (in my case black) plastic box at the back of the switch.
Am I right, that if I remove the 2 little nuts from the axes, I can pull down the plastic box from the axes then?
I'm asking this, because if this is possible, then I don't have to remove the whole front panel, etc. In this case I only have to desolder the fuse holder at the back of the switch, so I will get enough place to pull down the plastic box.
I think the pins on the rotary panel are clean, so I only have to clean the power pins in the plastic box, to get a fix contact immediately when I turn on the receiver, not just a few seconds later.
Thanks in advance.
 
Welcome Aboard, Helmut!

Your English is good - Probably far better than my Deutsche.

You can remove the power switch without dismantling the front face. It is a very tight area, but it can be done:

SX-550PowerSwitchAccess.jpg


Once the switch is removed it can be pulled out of the area without desoldering any wiring. Then the switch can be opened for inspection and cleaning. Only use cleaners and solvents which are safe for plastics. If you must abrade the contacts to restore a good surface do not use any aluminum oxide sandpaper. The particles will embed in the soft silver/bronze contact alloy and cause problems. Use only crocus cloth or flint paper, or a contact point file to remove the burned material. Since this is a common problem, there are several discussions about cleaning and restoring this type of Alps power switch but only a few mention the warning about aluminum oxide sandpaper.

When completed, apply a very small amount of white lubricant on the switch cam and be certain that nothing gets on or near the clean contacts. If you wish to preserve the switch and prevent it from ever failing again due to overload you might consider installing a power relay to supplement the switch. There are several discussions about that as well, including this: http://audiokarma.org/forums/index.php?posts/4688296/
 
Hi Watthour,

Thanks for your quick reply and help.
This is a really good news for me, that my notion can work. So I don't have to take apart the half of the receiver then build it again because of a messy contact in the switch.
I will follow your advice, and avoid to use of aluminum oxide sandpaper.
When you mention "white lubricant" do you mean something like heat resistant silicone grease? Usually I use that material to keep switch pins clean from oxide.
Here's a picture about my receiver's switch:
47lqMuo.jpg


Not the best picture, but probably you see that the axes end are above the fuse holder. So I think I have to desolder the fuse holder. Or am I wrong, and those are not axes with nuts at the back of the plastic box, but "screws" which I can remove? Because on your picture the 2 axes look much shorter.

I can't check it right now, because I'm at workplace. :)
 
If you're married, a metal finger nail file will also work to clean the contacts nicely. Ask the wife if she has a spare you can have. If she doesn't ask where you can get one. They do come in handy for small contact points.

White grease in this case means "White Lithium grease". You can get small tubes in Auto Parts Stores.
 
I had the faceplate removed in the photo, but did not have to remove the front chassis shell. This allowed the screws to be retracted enough to remove the switch without desoldering anything on the board. It also relaxes the tuner string and gets it out of the way. Even if the fuse holder is removed there will be a need to access those screws to allow removal and installation of the nuts holding the switch.

Consider it a good excuse to clean the front faceplate glass and dial.
 
Welcome Aboard, Helmut!

Your English is good - Probably far better than my Deutsche.

You can remove the power switch without dismantling the front face. It is a very tight area, but it can be done:

SX-550PowerSwitchAccess.jpg


Once the switch is removed it can be pulled out of the area without desoldering any wiring. Then the switch can be opened for inspection and cleaning. Only use cleaners and solvents which are safe for plastics. If you must abrade the contacts to restore a good surface do not use any aluminum oxide sandpaper. The particles will embed in the soft silver/bronze contact alloy and cause problems. Use only crocus cloth or flint paper, or a contact point file to remove the burned material. Since this is a common problem, there are several discussions about cleaning and restoring this type of Alps power switch but only a few mention the warning about aluminum oxide sandpaper.

When completed, apply a very small amount of white lubricant on the switch cam and be certain that nothing gets on or near the clean contacts. If you wish to preserve the switch and prevent it from ever failing again due to overload you might consider installing a power relay to supplement the switch. There are several discussions about that as well, including this: http://audiokarma.org/forums/index.php?posts/4688296/

If you're married, a metal finger nail file will also work to clean the contacts nicely. Ask the wife if she has a spare you can have. If she doesn't ask where you can get one. They do come in handy for small contact points.

White grease in this case means "White Lithium grease". You can get small tubes in Auto Parts Stores.

Thanks to Watthour and larryderouin I followed their guidance and was able to repair the power switch in my SX 450. My first attempt at electronic repair was a total success! I did not desolder the assembly from the board or remove the front chassis shell either. I did not move the transformer and did not desolder the fuse clip either. I did however bend the fuse clips towards the transformer (after removing the fuse) just enough to slide the switch housing off the two mounting shafts. I stood the receiver on it's left side so the power switch was right down at the table that way when I used an emery board (not metal) to file the contact points (after pulling them out of the grey plastic housing) the filings fell only two inches onto the inside left plate to a waiting damp paper towel. Once the switch housing was off it was easy to clean both sides of the rotary switchboard in place using deoxit and a soft toothbrush. After filing I re-cleaned the contact points and the housing and the rotary switchboard with deoxit and pipe cleaners. After reinstalling the housing I simply bent the fuse clip back to it's original shape. It is now working perfectly. The whole procedure took about 1.5 hours. Thanks again from a grateful noobie guys! :)
 
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Welcome Aboard, Helmut!

Your English is good - Probably far better than my Deutsche.

You can remove the power switch without dismantling the front face. It is a very tight area, but it can be done:

SX-550PowerSwitchAccess.jpg


Once the switch is removed it can be pulled out of the area without desoldering any wiring. Then the switch can be opened for inspection and cleaning. Only use cleaners and solvents which are safe for plastics. If you must abrade the contacts to restore a good surface do not use any aluminum oxide sandpaper. The particles will embed in the soft silver/bronze contact alloy and cause problems. Use only crocus cloth or flint paper, or a contact point file to remove the burned material. Since this is a common problem, there are several discussions about cleaning and restoring this type of Alps power switch but only a few mention the warning about aluminum oxide sandpaper.

When completed, apply a very small amount of white lubricant on the switch cam and be certain that nothing gets on or near the clean contacts. If you wish to preserve the switch and prevent it from ever failing again due to overload you might consider installing a power relay to supplement the switch. There are several discussions about that as well, including this: http://audiokarma.org/forums/index.php?posts/4688296/
 
Alps power switch cleaning thread to the rescue! All this applied very nicely to my Scott 350R receiver. My points were treated (filed and cleaned) according to this technique with excellent results. Unit powers up instantly where before it was a flickering and crackling. Note to any Scott owners, all you need to do is remove the bottom plate and the power switch is open to access on the bottom side of the receiver. Quite a bit easier than with the Pioneer. Thank you all who contributed to this thread, you made my day.
 
What useful postings these are! I have a Pioneer SX-450, bought in 1977. It's clean as new inside and out, but it has developed the flickering-lights and static problem -- and the problem does not go away as it used to do. I have seen here the very informative descriptions of how to remedy the problem by cleaning the inside of the rotary selector switch. Please, forgive my naive questions about how to open the black switch housing/case:

1. The two nuts that screw on the two rods at the back of the switch have to be removed first, right?

2. How does the housing of the switch open in order to expose the contacts? By looking at the black housing, I do not see a line on its top that would indicate that the front half can separate from the back half. Does the top half separate from the bottom half? If yes, how does one do that, and can it be done without removing the switch from its normal position? (I do not trust myself to start disassembling and desoldering all sorts of things. However, if I can carefully open the switch in place, I could reach the contacts with a small file [the kind used for old-car distributor points] and then give them the Deoxit treatment.

Thank you in advance for your response and patience with a novice, but an eager one to learn. (I did manage to repair the frozen platter and size-selector lever of my 1977 BIC 960 turntable with some wonderful help in a forum similar to this.)
 
Zebulon1: Thank you for the speedy reply. Yes, I had seen those pictures and they are very clear. Unfortunately, the black switch in my SX-450, unlike the grey one shown in the pictures, does not show any line where the front and back halves of the housing would come together! (Such line is clearly visible in the grey switch.) I know this does not make any sense, but I am wondering whether these two switches open in a different way. I hope I am wrong, but it looks like the switch in my unit was made so that it won't be repairable -- and only be replaced when it fails. I managed to inspect the sides of the switch housing using a dentist mirror, and I cannot see any line separating the two halves either. Does anybody know anything about this? I am tempted to do something dangerous: drill two small holes at the top of its housing and spray Deoxit inside the switch through them -- assuming that the drilling will not destroy something!
 
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Are you sure the switch is bad?
Did you short the switch and see if the set operates correctly?
You want to make sure it's the switch if your traveling into no mans land.
Some like me, like to have these receivers working per the spec's but other's will bypass the switch and use a remote switch like a surge protector.
I haven't seen any black switch as yet.
 
Deoxit will not fix this switch. The contacts are burned, not oxidized.

Thank you, redk9258. That's VERY useful information for somebody like me. It prevents trying wrong remedies.

Are you sure the switch is bad?
Did you short the switch and see if the set operates correctly?
You want to make sure it's the switch if your traveling into no mans land.
Some like me, like to have these receivers working per the spec's but other's will bypass the switch and use a remote switch like a surge protector.
I haven't seen any black switch as yet.

I have not tried shorting the switch. I'll do that. Thank you. I, too, want to have like to have equipment working as intended.
I have not done this before, but I'll try now to post a photo of my SX-450's black switch, which also shows the little fiber board (circuit board) in front of it, which, as I understand it, has the contacts that select the speakers (A, OFF, B, A+B).
 

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Hm, I responded to this, but it did not get posted! So that I do not duplicate, in case it shows up later, the short version is that the article was too technical for me. However, yesterday I fixed the flickering-lights-and-static problem of my SX-450. I'll post here a detailed description of what I did for beginners like myself -- and beg the indulgence of the more knowledge participants of this forum. The contacts inside the switch were not burned or corroded! They just did not touch each other well enough and tiny, feeble sparks were visible between them. My receiver now works perfectly -- no flickering lights and no static.
 
I finally have gotten the chance to write up how I fixed my Pioneer SX-450 flickering-lights-and-static problem. I post it here as a pdf file. It is written for beginners like me, so, the more knowledgeable people in this forum, PLEASE, excuse the details. Those are what we beginners need in order not to screw things up! And an additional note: With the OFF/ON switch removed, the contacts of the speaker-selector little circuit board are exposed and can be cleaned as needed, as described by other postings in this forum. Although mine were clean, I used Deoxit on them for good measure. It cannot hurt.
 

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Apologies for bringing this thread back to life. I just recently encountered the flickering light/dirty switch issue with this receiver. I was able to loosen the two nuts that hold the switch shell together without actually taking the nuts off. I then pried the shell open about 1/8th of an inch to spray some D5 inside...pressed the shell together and worked the knob back and forth. It works fine now. I know a physical cleaning is better than straight D5 but I was trying to avoid tearing the switch completely apart, potentially making the situation worse. Hopefully this will help someone in the future.
 
You may have bought yourself a little time but there is no spray that will fix this issue. The switch must be taken apart and the contact points filed down and then thoroughly cleaned and the switch reassembled and set back in place. I have done several of these Alps switches with good results.
 
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