• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer SX-950 Restoration Project

Part 10 - project complete and sounding fantastic now. Did some troubleshooting and rectified all issues above including installation of a new relay and cleaned up power supply connections. Obey all further alarms;)

 
Last edited:
Timothy Flath said:
Thought I would share my project video series from a restoration I recently did of a tired old Vintage SX-950 receiver I recently finished restoring. It now has a new lease on life and will still serve for many more decades to come. Jump to the last part to see the final outcome. Here is part 1:

Part 1 (General Intro and Case Build):
Click to expand...
 
Quick question, I'm having trouble sourcing these 512-KSC1845FTA transistors for my sx950 recap/upgrade. What are some substitutions that I should be looking at? If anyone could point me to a source for researching replacement for future issues like this, that would be awesome. Thanks!
 
I would not sub but find a source of them. Any ksc1845 would work. Lots of possible suppliers, Mouser, Digi-key, Newark, arrow and many more
 
Akram said:
I got an SX 950 for a very reasonable price and I am planning a full restore this winter. I was just going to buy a complete rebuild kit off E-Bay or somewhere, is there anyone that would advise of not going this route? I was going to get a complete Pioneer Spec 1 Preamp rebuild kit as well...

s-l1600.jpg
Click to expand...
You will most assuredly pay a premium for the kit on ePray but it does save a lot of work and research if you trust that the seller is buying what is best for you vs best for his/her pocket book. Then again if you are new to doing these types of refits you will soon be overwhelmed by the choices and options available out there. I went with the second route on all my work in this thread mostly because I wanted to learn. My 950 is still sounding fantastic so no regrets (so far)...:)
 
Akram said:
I got an SX 950 for a very reasonable price and I am planning a full restore this winter. I was just going to buy a complete rebuild kit off E-Bay or somewhere, is there anyone that would advise of not going this route? I was going to get a complete Pioneer Spec 1 Preamp rebuild kit as well.

s-l1600.jpg
Click to expand...
The difficulty I have with 'kits' is the seller may include parts you don't want/need, and not include parts you do want/need. I found that vetting parts lists (BOM) from AK works better and saves me the cost difference of the kit maker's markup profits. Then I order from normal, reputable vendors like Mouser, Digikey, Arrow, etc. I have also found, no matter how well vetted a list is, I always end up buying parts I decide not to use, and ordering more parts I figured out later I needed, or a greater quantity than my original order. Most inexpensive parts like small signal transistor, or caps I have learned to just order the next 'price break' quantity and keep them in stock. Note that I am not 'in the business' of audio repair, but I do build some hobbyist custom electronics, so the extra parts are useful anyway.
 
Well, I finally started my SX-950 rebuild. I've hit my first snag, though. Recap and transistors on the Flat amp and Tone amp boards, but after finishing all caps and transistors on the power supply board (AW101) I'm having issues. I've tested after each board, and everything worked great. After the 101 board, I heard the protection board click on then off again, then nothing. (I have this on a dim-bulb, just in case, bulb never went bright) Then after powering off and checking connections, it just immediately blows Fuse 4 and 5. I've checked all cap polarity and transistor orientations, all look good. All diodes above the fuses test good as well (in circuit). I've looked for any loose wires between this board and others, all looks good.
Since fuse 4 and 5 seem to work with Q 8-9-10, I'm going to try removing them, checking on the tester and reinstall.
Any ideas?
Also, is there any way to keep from going through a bunch of 1amp glass fuses while testing something like this? Maybe a temp circuit breaker that could fit in place of the fast blow fuses? Just a thought, haha!
 
Suggest to Go back a recheck the part pin outs and placement orientations, always good to reference the device data sheets
remember the drawings show the pcb bottom or backside
When you are blowing fuses it is better to troubleshoot with the ohmmeter
 
You can use 100 ohm 5 w power resistors in place of the secondary fuses. Monitor the voltages if too much voltage ( because of too much current drawn or short) drop shutdown immediately, back to ohmmeter
 
I found that either Q8 or Q9 had blown/shorted. I replaced both with the original transistors and now I don't get blown fuses. I get no other lights, though, nor any action on the protect relay, but I'm getting voltages, so I'll start tracking it down that way. Here's the first few quick measurements:
Collector of Q8 I get 26.5vdc, schematic says 23.8
Collector of Q9 and Q10 both get 26.7v schematic says 16.5...

Measurement on pins 2 and 3 should get 5.4v but I get 0
Up on collector of Q1 I get 63.3 when schematic says 60.7, other points up there seem close as well.
It seems to just be this segment on the bottom of the schematic.
Any suggestions on what to measure next to get more info?
(All pinouts seem to be fine on all transistors as well as polarity of caps) Maybe a diode is shorting?

Thanks for any input, I'll start a new thread if this goes beyond the issues Tim had with his rebuild.
 

Attachments

  • schem1.jpg
    schem1.jpg
    138.5 KB · Views: 15
Last edited:
Looks like I have the same zener diode blown that Tim did in his rebuild - ZD2, is says it's a WZ-130 so I've ordered a 0.5w 130v replacement (only have random ones here that I can't be sure of).
I've included a pic of the voltages I am able to pull since I replaced the above transistor that was blown (and might have been responsible for the zener going open, or visa-versa).

Hopefully this will get me back up and running, I would like to get on with this rebuild! haha
 

Attachments

  • 20211013_z2.jpg
    20211013_z2.jpg
    156.6 KB · Views: 16
Akram said:
I got an SX 950 for a very reasonable price and I am planning a full restore this winter. I was just going to buy a complete rebuild kit off E-Bay or somewhere, is there anyone that would advise on not going this route?

s-l1600.jpg
Click to expand...
Who did you buy the Kit from, and how much$? How was the documentation?
many to choose from. I have some bad luck w the last kit I bought.
Looking at buying a kit for my SX-1250 and maybe more units.
 
You must log in or register to reply here.
Back
Top Bottom