Pacific's SX-1980 restoration - 33 photos!

[Pacific Stereo]

I know I teased everyone with having three 1980s in the lab. Well, the first one is done, and she has come out wonderfully. This unit is just gorgeous, and is now making beautiful music. Ready to have a look at one of these very rare birds?

This is the unit on the bench, right out of its box (the owner still has the original box!).



Dirty, and there's a lot of corrosion on the RCA jacks (not shown). Switches and controls are dirty, intermittent and not happy. A look at the inside reveals years of dust. Even the covers for the front end and the PLL board are icky.



The first thing to do on these is get the power supply overhauled and stable. These suffer from both Pioneer's standard "bake, bake, bake" philisophy and also from a bad choice of designs for a current source. Apparently, Pioneer graded a particular FET and selected ones that could withstand a higher-than rated voltage (50, vs 35). Maybe not so bad when parts are plentiful and in the Pioneer warehouse, but not so good when those parts are now very rare (and not graded). Here's what the supply looks like.





This supply has been repaired before. The FET was changed, and a few other parts were replaced as well. So aside from a recap and upgrade overhaul, we have to solve this current-source issue. The solution is to replace the FETs with a little hand-built circuit that will supply the required amount of current and do it while remaining immune from temperature and voltage variations. Here's a look at what that looks like.



And here it is running, making the required current. I've made six of these, and they all are within .01mA of each other. I can live with that!



At this point, I'd like to acknowledge both Echowars and Mark the Fixer over at AK for adapting and testing this wheel, saving nitwits like me the trouble of having to do it. Thanks, guys!

So with those made and installed, we recap, replace some semiconductors, clean up carbon glue, and refurbish. And yes, that missing screw in the photo is not actually missing.



We use radial parts laid down, because they are both cheaper and better parts than any of the axials you can get. It's hard to see, but the FET replacements are running in this shot. Since this photo was taken, I have changed the way I do the capacitors in these, so the PS boards now look a little different from this one.



The next things to do are the power amplifiers.



Unlike a number of similar Pioneer receivers, there's not much to do to these. We don't change out any semis, all these get is a recap, repair of bad solder and new multiturn bias and offset parts. We also clean the pins and the plugs that grab them. Hey! This rebuild stuff is easy!

EDIT: After doing more than a few of these, I do now change a few semis in the power stages, for preventative purposes.



And before we move on, here's a look at the bottom before...



...and after.



The next step is working on the control amp section. Here's a look at the unit filleted for overhaul. You can see the flat amp, tone, filter, mic/phono settings, input, filter and headphone/meter boards here.



Let's start with the flat amp.



We replace caps, and clean and treat switches and controls. Nice Wima films and Nichicon audio grade parts go where they need to be. These photos don't reflect this, but I now also change the semiconductors on the flat amp, tone and filter boards.



All right, let's move on to the tone board. Here's before.



Gah. Electrolytics and tantalums EVERYWHERE. We change as many as possible for nice film parts, the rest have to be low-leakage electrolytics. In the signal path with tone defeated, there are now no electrolytics at all, only films. Of course, we clean and treat the controls.



Moving on to the filter board...



Tantalums, tantalums everywhere! They go bye-bye. Hellooooo, Wima!



We'll skip the function board, as there's really not much to see. But here's the headphone board.



We don't change those pots since all they do is set meter calibration, and they work fine.



The mic board isn't particularly exciting. We'll skip that. But the phono board needs attention.



It gets new output transistors (the phono stage is a mini power amplifier), new caps and is much happier, now. Same story here, I now also change more semiconductors on this board.



And now, let's move to the top of the unit. Here's what she looks like after some TLC. Better, no?



I forgot to take a "before" photo of the PLL board, but here's what it looks like after we're done with it.



Next comes the tuner section. Caps, caps, everywhere! Must go!



So we get rid of all those dried-up, worn out parts and freshen up with new. We'll follow this with a complete alignment of the AM, FM, MPX and PLL sections.



And there's parts. Care to count how many caps got changed?



After an overnight burn-in and recheck (all good!), she can go outside for some photos. I know, I know, I made you wade through all of the stuff above to get to the shots of the unit after BeautyMaker treatment. So here they are.









And now, the one I know y'all will like (I see Image of the Week in this unit's future!)



What a beauty. And sounding better than she did when she was new. Now, I get to go and do this again. And again!

Copyright notice: All photos copyright 2013, Pacific Stereo. All rights reserved. Absolutely no use without written permission. eBay use will definitely get you a VERO termination!

[Socal Sam]

Ah heck, I sold all three of my SX-1980's before I could get them to your bench. Superb as usual, I had to towel off my keyboard. Drool, you sickos!

So, with film caps everywhere in the preamp section, the sound must be different from the original SX-1980. I always thought the original to be a little slow and a little compressed. Despite the immense power on tap, the was a layer of something to get through to the music. I suppose if the 1980 was paired up with HPM-100's this veiling is perfect compensation for the shrill that are the paper tweeters.

I digress. What does the Pacific Stereo SX-1980 sound like and how does it compare to the original?

[Pacific Stereo]

Well, this is a difficult comparison to make, because the unit in its original state wasn't sounding very good, mainly due to the condition of the switches and controls. I can tell you that during the overnight burn-in, the sound definitely changed for the better. Must have been the Mexican radio I was playing! I would say that in comparison to my SX-1080, it's most definitely slower, but I wouldn't call it compressed. It's got a smooth and easy character to it, and I like it.

[Freddy1]

Soo, How much you sellin' this beauty for?

[Warped Bezel]

Sorry, Freddy, they are all restorations for customers...

[Freddy1]

RATS! Just my luck..............

Originally Posted by Warped Bezel

Sorry, Freddy, they are all restorations for customers...

[Warped Bezel]

Originally Posted by Freddy1

RATS! Just my luck..............

I've got a few SXey 1980s receivers but I know that doesn't work

[chicken]

Originally Posted by Pacific Stereo

And now, the one I know y'all will like (I see Image of the Week in this unit's future!)



What a beauty. And sounding better than she did when she was new. Now, I get to go and do this again. And again!

Copyright notice: All photos copyright 2013, Pacific Stereo. All rights reserved. Absolutely no use without written permission. eBay use will definitely get you a VERO termination!

That picture is sooo good, what a beautiful little thing!

[Freddy1]

That picture would make a great wallpaper for your computer........

Originally Posted by chicken

That picture is sooo good, what a beautiful little thing!

[oldaudioscho]

Originally Posted by Freddy1

RATS! Just my luck..............

You should see my SX1080 he rebuilt, or more importantly, hear this receiver. It had a couple of issues that he fixed and the unit came back looking and sounding like it was new just off the shelf. The man is a true dedicated tech and this site wouldn't be the same without him. Keep up the great work P.S.

Ron

[chicken]

Originally Posted by Freddy1

That picture would make a great wallpaper for your computer........

It sure would, it would be aces for advertising too

[HeadGap]

WOW!!... That’s another impressive rebuild. I like the use of the Wima film capacitors in the audio stages. I'll half to try some.
Not sure I understand. Are those 2 circuit boards replacing a couple of FET's in the regulator section of the power supply to improve stability?
At any rate it looks and I’m sure sounds very nice.
I like the pictures, that evening shot with it all lit up is sweet.
I still think the Concept's looks better though.

Jeff

[Loudenuff]

WOW! Very nice job! Some day when I have the cash you will get my 16.5 to re-build. Hopefully sooner than later. Well done!

[Pacific Stereo]

Originally Posted by HeadGap

Not sure I understand. Are those 2 circuit boards replacing a couple of FET's in the regulator section of the power supply to improve stability?

Not stability, reliability. Those boards take the place of two FETS and their associated circuitry, because Pioneer used parts that were rated for 35 volts and by grading their own supply of them, found parts that were good to 50 volts and used them. It's not a particularly good design in the first place, and it's made worse by the fact that the parts are being used beyond their design capacity. Compound that with the fact that the graded parts are NLA, and you've got trouble. This design circumvents all of that and works great.

[Warped Bezel]

Originally Posted by chicken

It sure would, it would be aces for advertising too

That's what I told him...incorporate it as the main part of his homepage. It's one of the nicest gear shots I've ever seen!

[HeadGap]

Originally Posted by Pacific Stereo

Not stability, reliability. Those boards take the place of two FETS and their associated circuitry, because Pioneer used parts that were rated for 35 volts and by grading their own supply of them, found parts that were good to 50 volts and used them. It's not a particularly good design in the first place, and it's made worse by the fact that the parts are being used beyond their design capacity. Compound that with the fact that the graded parts are NLA, and you've got trouble. This design circumvents all of that and works great.

OK... That's great!... I guess even the origional design engineers don't always get it right.

Jeff

[NEMOaudio]

Originally Posted by Pacific Stereo

And now, the one I know y'all will like (I see Image of the Week in this unit's future!)

[/SIZE][/B]

IMAGE OF THE WEEK
June 30 - July 6, 2013

Oh yes, we realy like it. (the picture and your work too)

[ke4mcl]

Ive seen those turn up at hamfests and never paid attention. I recognize the power supply in it though. Guess i should pay better attention to big receivers!

[Bandwidth]

Originally Posted by chicken

That picture is sooo good, what a beautiful little thing!

Great picture. And it IS beautiful. "Little" it ain't!!

[chicken]

Originally Posted by Bandwidth

Great picture. And it IS beautiful. "Little" it ain't!!

I didnt realise it was a big thing :O Ooopsy :-)

Nice to see it got image of the week too!