Pioneer SX-1050 recap and service

I got a SX-1050 from a good friend to recap and go over. I'm going to be doing a lot to it, cleaning, recapping, replacing weak, stressed or defective transistors etc. Basically get it as close to new again as I can get it.

 Here are photos some of the boards before the recap and servicing, the more of them will follow as I get to them.

Tuner board before service:

EQ amp, or phono amp before service:

Tone amp before service

I forgot to get a before of the flat amp board, but it looked a little like the tone amp does.

Protection board before service:

Power supply board A before service, it's already had a few caps replaced on it, two are good Nichicons, but the other two are cheap Chinese caps and not something I'd ever use, even if you paid me to.

Power supply board B before service

Cheap Chinese caps used again, one has already blown up on my friend and was replaced by the tech who put them in originally with the same kind of cap! How dumb is that?

Here's the blown cap:

Power amp board before service:

I did a little on the power amp board, there's not a whole lot I can do until I get the caps and stuff from Mouser. The pins for the output transistors needed to be cleaned big time.

Left channel pins before:

And after!

Right channel before:

And after:

Much better! More will follow, I need to order the caps after my friend decides if he would like the tuner board recapped or not, and then they won't arrive until next week.

Moving on to the protection board, one thing that caught my eye was that one of the contacts in the relay looks like it's bent. Huh? I take it out, and sure enough, somebody's been in it before me and broke one of the little plastic tabs that hold the cover on and the little plastic piece that holds the contacts on the relay!

The relay:

The bent contact and broken plastic piece:

My friend has said okay to the repair estimate, caps, transistors and relay have been ordered, should be here by Wednesday if they ship Monday. For now it's just a waiting game. Well okay, not really, I have stuff around the house to do, and I kickback and listen to the receivers and HPM's that I have during the evenings. Currently have the SX-1010 running (the second one).

Update 10/26: they shipped Tuesday, a day later then I thought, so they won't arrive until tomorrow or Friday, depending on the mail service

Update 10/29: they're here! After being missent twice! and pushing back the delivery date to today (they would have arrived on 10/27) they are finally here! Kind of funny though as the replacements for the main filter caps (I'm doing those too) arrived today as well, so it all worked out.

And here are the photos!

The parts:

And the boards after!

Tuner board, 20 caps were replaced:

EQ amp board, 10 caps and all 10 transistors were replaced. Q1-4 on here were gain matched (the four in the middle next to the "AWF"):

Flat amp board, 16 caps and all 6 transistors were replaced:

Tone amp board, 26 caps and all 4 transistors were replaced:

Power supply board B, just three caps on here, also checked all the fuses for corrosion and correct rating:

Power supply board A, 15 caps and all 13 transistors were replaced, two of them were upgraded to a bigger TO-126 case style for better heat dissipation. New heatsink grease was added to the ones on the heatsinks.

Power amp board, only 8 caps and 4 transistors on here, the 4 being the differential input pairs for each channel, the replacements were gain matched:

Left side:

Right side:

Protection board, 6 caps and 2 transistors, the relay predriver and driver were replaced along with the relay. The driver was upgraded to a bigger TO-126 case style for better heat dissipation.

New filter caps in the clamp:

New versus old 

And the filter caps in place!

Here is the top view and bottom view of it completed and cleaned:

Not shown is the filter amp board, there were 4 caps and two transistors on it. In total, 112 caps including the filter caps were replaced along with 41 transistors and 1 relay, for a total of 154 components. Testing went off without a hitch, DC-offset and bias set perfectly and it's been playing for a day and a half now through my HPM's with no problems at all. The difference between the before sound and after sound is like night and day, it sounds so good I think I might just keep it! Okay, not really, my friend wouldn't like that (you reading Chris?) :-D

Here are the photos with it put back together!

It has been playing without a hitch for almost a week now and the sound of it is just amazing. I now know why people want this receiver! It won't sound like this without a restoration, but if it's fully restored like I've done to this one, you will have one heck of a receiver. This concludes this post, please feel free to leave comments, ideas or questions, I will be happy to answer any questions.