Pioneer SX-1050 brought up from the depths...

[leesonic]

Here is a Pioneer SX-1050 that a fellow AKer sent me to work on. It had been in a storage unit he said, and neither of us realized it was that dirty inside until I got the covers off. One good thing about it is the front panels and knobs are in pretty good shape, they just need a thorough cleaning.



Inside, it has a bunch of rust, dirt, and dead spiders. You might also notice that wires had been cut and spiced together (circled in red). The power supply board was missing the mounting bracket, and was just flopping around inside.





One other good thing about it is that it actually works of sorts. The two main caps looked kind of dodgy, one was bulging on the bottom, so I pulled the wires to the main bridge rectifier. Powering it up, it worked fine as a preamp, so maybe the cut wires from before were due to problems with the power amp?

The plan we established is for me to re-work the insides without paying too much attention to how it looks, instead fitting new components, upgrading where necessary. The exterior can be cleaned up and made to look presentable.

Lee.

 

[leesonic]

The power supply board looked like it had the most components on, so I removed it to work on it. Yeah, I cut the wires. If that makes me the demon, or a bad tech, so be it. I wrestle with SMD components all day at work, some smaller than the last thing I picked from my nose, I wanted to make this as easy as possible. Plus, this is a big beast to be throwing around on the bench.

Here is the power supply board removed from the case. I don't know why the picture is rotated like this.



And here is it minus all the components I am going to replace. With the caps and transistors off, I cleaned it with acetone.



On some of the other rebuild threads, I've seen people replace the 10 ohm and 100 ohm resistors. Since the ones on here look good, I didn't think I needed to replace them. R7 and R16 look to have been getting a little warm, I wonder if I should replace them with 1w resistors, use the 0.6w I have in my parts bin, or leave them? As I said before, it worked fine without the power amp stage connected, maybe these resistors just run hot? I have the zener diodes, I just hadn't taken them off when I took this picture.

Lee.

 

[antv20]

It’s happening!!!

 

[EngineerNate]

When in doubt, fresh metal films are cheap insurance.

 

[ivandezande]

For sure replace those toasty ones with something beefier, totally agree with the above post. It's worth the extra 80 cents or so.

 

[leesonic]

Rebuilt power supply board.

 

[leesonic]

It’s happening!!!

With all the speed of an advancing glacier...

 

[leesonic]

Another power supply board. Keen eyed observers might notice the wires that have been taped up with electrical tape, not my doing.



The bridge rectifier for the main caps is mounted on a heatsink. Knowing how Pioneer run some components very hot, this must be getting warm for them to even consider putting a heatsink on it. I removed it and replaced the heatsink grease with new stuff.



New caps and diodes. The taped wires to this board I repaired, using two layers of heatshrink tubing.



Lee.

 

[Oldsansui441]

Looks good, nice work Lee. Am guessing you took the photo prior to finishing up pins 2 and 3.

 

[leesonic]

The two main caps looked kind of dodgy, one was bulging on the bottom, so I pulled the wires to the main bridge rectifier. Powering it up, it worked fine as a preamp, so maybe the cut wires from before were due to problems with the power amp?

 

[Oldsansui441]

Ahh l see, fair enough.

 

[quaddriver]

ok, point of order...when you phrase 'bringing up from the depths', we need to see evidence it was on the titanic or at least andrea doria...

those pics were nicer than half the stuff listed as 'fully working, rare collectible, not tested' units on ebay....

 

[antv20]

ok, point of order...when you phrase 'bringing up from the depths', we need to see evidence it was on the titanic or at least andrea doria...

those pics were nicer than half the stuff listed as 'fully working, rare collectible, not tested' units on ebay....

As the one who sent the unit to Lee, the unit was stored in a non-climate controlled storage building for at least 15 years. Both of us where hesitant on deciding whether it was even worth reworking the unit.

**i had nothing to do with the handy work done before it was sent to Lee. Dad was storing it for someone and was getting ready to throw in the trash when I saw it.

 

[Silentnet]

Watching this with great interest. Lee, if you aren't too busy you may end up with my SX-1250 at some point. It's in similar shape after years of neglect. Though I shudder to think what shipping will be to NJ...

 

[antv20]

Watching this with great interest. Lee, if you aren't too busy you may end up with my SX-1250 at some point. It's in similar shape after years of neglect. Though I shudder to think what shipping will be to NJ...

Shipping was around $60 for the 1050 from Western Ky.

Lee does great work. I purchased a Technics 1600 that he restored. It has performed flawlessly since I received it.

 

[leesonic]

ok, point of order...when you phrase 'bringing up from the depths', we need to see evidence it was on the titanic or at least andrea doria...

Here is the proof :

 

[leesonic]

Watching this with great interest. Lee, if you aren't too busy you may end up with my SX-1250 at some point. It's in similar shape after years of neglect. Though I shudder to think what shipping will be to NJ...

I'm not sure I'll be doing many more of these big receiver restorations. I'm currently 10 hours into it, and nowhere near finished. If I were to put an hourly rate on my time, I would probably only be getting $10 an hour.

Lee.

 

[leesonic]

Tone control board before :



And after. Look at all those red Wima film caps. New transistors as well.



Phono board before :



And after. Again, red Wima film caps in the signal path, Nichicon PWs elsewhere, and all new transistors.



Lee.

 

[Oldsansui441]

Here is the proof :

Always thought Pioneer's had pretty good anodizing .

I'm not sure I'll be doing many more of these big receiver restorations. I'm currently 10 hours into it, and nowhere near finished. If I were to put an hourly rate on my time, I would probably only be getting $10 an hour.

Yes for sure, they are very time consuming. I think l put about 30-40 hrs into my SX-939 but l recapped the tuner board and it also had major FM problems. You are right about the hourly rate on these things, no wonder businesses aren't keen to take them on plus is a customer going to pay $2000.00 + for a rebuild on one of these, l think not.

Nice work on the tone and phono boards.

 

[leesonic]

Looking at the back of the flat amp board, it looks like someone has been there before and cut a trace. This trace appears to be for the loudness tap on the volume control, not sure why only one side is cut. I wonder if our resident Pioneer guru @markthefixer has seen anything like this. I joined the trace back together.



Here are the new caps and transistors on the flat amp board, I forgot to take pictures of it with the old caps on.



Lee.