Pioneer SX-1050, both happy and concerned.

[Coyote13]

Hi all! New to the forum and the vintage audio world, and I just managed to pick up a pioneer sx-1050 off ebay with the tagline of powers up but no sound. I thought as long as the transformer worked it would be worth the risk, but during the post auction obsession that I go through the day after every ebay win, I noticed that the preamp to amp bridge was missing. So I ordered repro parts off ebay and low and behold it sure does have sound after all.


So I'm suuper happy right? Of course there's no lemonade without the sour. So the unit has a few issues that I'm not sure what to do about. The biggie and why I'm not just lurking anymore is the amp transistors, and their backing plate.






Now in another application I would pull it apart and take a shop cloth with a little oil on it and rub off the surface rust to see if there is any pitting and go from there. Hooowever, I'm not sure if that's a good idea for the base plate, and doing that to the transistors just smells like the wrong idea. Of course, I don't know, so here I am hat in hand asking more experienced people if either one would be ok with alittle bit of the old oily cloth or if that would be a hilariously bad idea?

 

[Watthour]

Whatever method you choose to remove the corrosion will probably be just fine - Short of sandblasting. Oil would not be a problem since it is generally an insulator, but it would be good to remove the existing corrosion in critical areas whether or not you apply oil.

The top/outer side of the transistor is almost irrelevant. As long as the connection between the mounting screw and flange is clean and tight, it should function correctly.

Speaking of shorts, it would be good to mark the output transistors' locations, remove theM and their insulators, and then deal with the TO-3 sockets in whatever manner you desire. Cleaning the heat sink and transistors, and cleaning or replacing the insualting mica washers, and applying a thin layer of fresh zinc oxide heat sink compound would be prudent.

If the rest of the unit is also that dusty, an overall cleaning may be in order. And if there is similar corrosion through the entire unit, more work would be indicated.

 

[Coyote13]

Whatever method you choose to remove the corrosion will probably be just fine - Short of sandblasting. Oil would not be a problem since it is generally an insulator, but it would be good to remove the existing corrosion in critical areas whether or not you apply oil.

The top/outer side of the transistor is almost irrelevant. As long as the connection between the mounting screw and flange is clean and tight, it should function correctly.

Speaking of shorts, it would be good to mark the output transistors' locations, remove theM and their insulators, and then deal with the TO-3 sockets in whatever manner you desire. Cleaning the heat sink and transistors, and cleaning or replacing the insualting mica washers, and applying a thin layer of fresh zinc oxide heat sink compound would be prudent.

If the rest of the unit is also that dusty, an overall cleaning may be in order. And if there is similar corrosion through the entire unit, more work would be indicated.

Thanks for the info!

Outside of those amp transistors it doesn't have much corrosion, which is why I was shocked to find that the rca jacks are so bad that the plating is gone and the copper has gone green.


(this is after cleaning with deoxit, giving up and hitting them with a dremel felt polishing pad)

I've ordered some replacements off ebay that were in good shape (from the same seller that I picked up the reproduction am antenna arm and a reproduction tuner knob, both of which I was very impressed with).

Also not sure how to remove the rust from the antenna connections and the phono ground.

For as corroded as the amp transistors and the back jacks are I was shocked at how dry the wood was (pretty much a lost cause, have a walnut case coming), and that the rest of the unit had little to no signs of corrosion.

 

[Coyote13]

Sitting on break and thinking about rust, and I started to wonder. Has anyone ever blued those sockets? I mean it appears to have a nice layer of rust with no pits, so if i took out the sockets boiled em to convert the rust then used my carding wheel it should turn into a nice layer of bluing. Would that be a problem? I mean I'd have to take the bluing off the post to reattach the wire by soldering so that shouldn't be effected there. Anyone see any problems with the idea that I'm missing?

 

[Watthour]

That should not be a problem at all, other than it's going to take some work to get it done.

 

[Coyote13]

That should not be a problem at all, other than it's going to take some work to get it done.

Yeah, not sure if I'm going to do it, but anyway you slice it I have to get the active rust off those sockets.

 

[Bill S]

You can try taking one of those slip on pencil erasers and work it back and forth on the input jacks to see if it removes the corrosion. A more aggressive approach would involve polishing with strips of 800 - 1000 grit sandpaper. Clean the insides with pipe cleaners wetted with some contact cleaner.