Wednesday, November 3, 2021

Up Next On The Workbench....

 I'm slowly working my way up the "Pioneer SX Food Chain", starting with the SX-780 I bought earlier this year. I've always liked the big Pioneer receivers since I was in college, and have wanted to get one for years.

In the process of going through my SX-780, I learned a lot about the Pioneer SX series of receivers. There were basically two series of these receivers; the SX-xx50 series, and the SX-xx80 series. The consensus among the audio forums is the the "50 Series" receivers were built better than the "80 Series", one of the main differences being the output devices used for the power amplifier that drives the speakers. The 50 Series used regular transistors, while the 80 Series used "Power Hybrids", which are several transistors mounted in a much larger package. The transistors are still available from numerous sources, while the power hybrids are close to being unobtainium. Some "audiophiles" claim the 50 series sounded better, but either series is capable of very, very good audio delivered to the speakers.

The 80 Series receivers had analog meters that showed the power being delivered to the speakers, while the 50 Series lacked these meters. I like the 80 Series, so that's what I've been looking for.

This is the newest one I just obtained. 

The seller said it was "tested", but that not all the inputs were checked, so all they could verify was that it worked on AM and FM, which means the output devices are working, a nice thing to know. They also offered a 90-day warranty (you get you money back), so since the listing was "$900 or best offer", I offered them $500, and they accepted it after a few emails back-and-forth.

When I looked at the listing pix, I noticed what appeared to be some kind of crud on the top cover, along with a spot of rust, as seen in the lower middle of the first picture:

We were dickering over the price when I asked if the unit had gotten wet, or was stored in a damp area, and they said they didn't know, but that "It Might Need Servicing", and was I comfortable working on these. I assured them I didn't have any issues with it needing a bit of work, and they accepted the offer.

It arrived here on Monday, superbly packed, and I took it downstairs and began to check it out.

The spots of crud on the cover....


....turned out to be rust under the paint, and as soon as I hit the cover with a wire brush, the paint just blew off: 

This bad enough that I'll go over it with my orbital sander, and then prime it and paint it. We're expecting very nice weather through the weekend, so this will be one of the last "Garage Tasks" I'll do before Winter sets in for real.

And The Wettening did a bit more than damage the cover. The rust spot on the top cover was directly over the power transformer, and whatever leaked in did this to the power transformer:

 I've already pulled the mounting hardware so I can clean this up, but not wanting to remove all the leads coming out of the end bell (the rusty part), I'm going to clean it in place, then very carefully mask everything around it, and repaint it.

The cover and end bell on the transformer are the only places I can see any evidence of water ingress, and the rest of the chassis is dusty and dirty, but not corroded:

So it looks like I may have "lucked out" on this one. There's no way I would have paid the asking price ($900) for this, but the seller was reasonable, the packing job was excellent (foamed-in-place), and it appears to just need a good cleaning and spot of paint.


  1. Replies
    1. The one I just got I'll keep. I'll resell it on my way up the food chain, probably in a few months, but I'll keep it for now.

      The SX-780 will go on the block when this one is finished.

  2. Those were nice back in the day. I couldn't afford one... sigh

    1. I couldn't, either. Well....I *could* have, but it would have come out of my racing budget, and that took precedence at the time....

  3. Excellent score. Gonna replace electrolytic caps? I would based on age alone.

    1. Thanks. I'm not sure if they "need" it. They show no signs of leaking or bulging, and since the seller "tested" it, they've already been hit with full voltage. I'll bring it up slow on the variac when I'm done, and monitor the leakage current on the main caps in the power supply. I generally replace all the power supply supply caps, but these were pretty high quality units at the time. One problem I've found is that new caps are physically smaller and sometimes require getting a little creative to mount in the old space.


Keep it civil, please....

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