Pioneer SX-636 Project

[trump]

Hello everybody, I am pretty new posting because I only recently bought a vintage receiver on ebay, a Pioneer SX-636. It was about $160, not sure if I overpaid or not but you live and learn right? So far, I've only cleaned it up using contact cleaner and dish soap/water for the faceplate and knobs. Everything seems to be working for the most part except for the FM indicator lamp which I've already ordered a whole new set of lamps from dgwojo.com. The first thing I want to do is replace the fm indicator lamp & the main dial lamps.

However, a bigger concern of mine is the FM reception/signal strength. When using the FM tuner, only 2-3 channels come in clearly and they come in very clearly with no static at all, and the stereo light turns on as expected. The problem is all the other channels is just static. Why would 2-3 channels come in perfectly clear but the rest just pure static? I've read the blue sanyo caps can cause issues but are those related to getting a FM channel to come in or the sound itself? Because when a channel does come in, it's crystal clear. I tried using contact cleaner on the brass contacts in the FM tuner itself but still only 2-3 channels come in. Could there be some interference going on or just a weak antenna?

Sorry if I am asking obvious or stupid questions but thank you ahead of time for the help!

Edit: I plan on fully recapping and doing whatever else is needed but I am not sure if the FM issue is related to that or not..thanks guys!

 

[ivandezande]

Could be caps, alignment, dust, etc....
$160 is a bit much. I had trouble selling a completely restored one on eBay for $120 not too long ago.

 

[trump]

Could be caps, alignment, dust, etc....
$160 is a bit much. I had trouble selling a completely restored one on eBay for $120 not too long ago.

Yes, I figured $160 was a bit much but it does cost a lot to ship these units, and it's in good working order for the most part I just want to figure out this FM issue even though I'm not sure how much the FM will actually get used. I already got all the dust/corrosion out for the most part so I think it must be caps somewhere..I just wasn't sure if the caps can cause channels not to come through clearly or if it was something else. Thank you

 

[markthefixer]

what is FM reception like on OTHER FM tuners for your location?

IF you have it open, take a few pictures of the boards w/ components so we can see whether it's stone cold factory or if it's been worked on.
If stone cold factory, there are a few transistors that should be replaced to ensure longevity in the power amp circuits.

If it HAS been worked on, restoration wise, the 160 becomes less injurious and more reasonable.

 

[trump]

what is FM reception like on OTHER FM tuners for your location?

IF you have it open, take a few pictures of the boards w/ components so we can see whether it's stone cold factory or if it's been worked on.
If stone cold factory, there are a few transistors that should be replaced to ensure longevity in the power amp circuits.

If it HAS been worked on, restoration wise, the 160 becomes less injurious and more reasonable.

I haven't tried any other FM tuners in my apartment (don't have any) but driving around the area in my car I get good reception for a lot of channels and the few channels I do get with the Pioneer are very clear.

Is there anything specific you'd want pictures of or just every circuit board? My guess is that it's factory because there was a decent layer of dust when I first opened it up but I could be completely wrong on that. I didn't see any bulging caps or anything like that but maybe a trained eye will see something that I missed. I uploaded a full res picture of the entire inside but I can get more detailed pictures tonight of each component.

edit: added full res picture

 

[markthefixer]

Well, In the tuner I see 6 sky blue sanyo electrolytics, 3 in the stereo decoder, 1 at the am out and 2 at the FM out - these eventually fail so we preemptively replace them.
BUT
they wouldn't do what you are seeing - it probably needs a tuner alignment. That will regain lost sensitivity.
need special plastic tools and usually special signal generating equipment.And skills that are becoming a lost art.

as an aside I see two transistors in your power amp that are a type we also preemptively replace, and some others we do at the same time - and also usually adding NEW trim pots for adjustments on the power amp board. The pots corrode internally, or those transistors self destruct - taking the amp with them.
granted the parts are inexpensive to replace, but who wants to spend 20 extra bucks for parts we would have been able to keep.

A lot of caps that do fail, fail because they dry out (bass starts to suffer, and the highs get muddy) and lose capacitance - and I see a bunch of those in there. Lists of them can be found in this forum. There are also transistors we do the same with - I have had people complain that their "recap" didn't improve the sound, and after questioning admit that they ONLY did the caps, and NOT the recommended transistors at the same time. Then under my direction they did the transistors too, and came back singing praises for the increased sound quality.

 

[rncpps]

I echo MTF's remarks. I have rebuilt quite a few of the SX-X3X and SX-1010 receivers and without exception recapping only provided marginal improvement (assuming one or more caps were not shorted). The real improvement came with replacing all troublesome transistors. Search AK. All the info is here! Pay attention to Mark's posts; they are the bible on anything vintage Pioneer. There are another handful of gurus here also; you will thank them all when you start the vintage bug. Without them I would never have even had a chance! Good luck! Welcome to AK.

 

[UncleBingo]

I think what you paid is totally reasonable for a unit of this build-quality. These are nice enough to be keepers when restored.

 

[superdog]

I had a nice one a few years ago(7-8) and would have been hard pressed to get $50 back then.

 

[trump]

Well, In the tuner I see 6 sky blue sanyo electrolytics, 3 in the stereo decoder, 1 at the am out and 2 at the FM out - these eventually fail so we preemptively replace them.
BUT
they wouldn't do what you are seeing - it probably needs a tuner alignment. That will regain lost sensitivity.
need special plastic tools and usually special signal generating equipment.And skills that are becoming a lost art.

as an aside I see two transistors in your power amp that are a type we also preemptively replace, and some others we do at the same time - and also usually adding NEW trim pots for adjustments on the power amp board. The pots corrode internally, or those transistors self destruct - taking the amp with them.
granted the parts are inexpensive to replace, but who wants to spend 20 extra bucks for parts we would have been able to keep.

A lot of caps that do fail, fail because they dry out (bass starts to suffer, and the highs get muddy) and lose capacitance - and I see a bunch of those in there. Lists of them can be found in this forum. There are also transistors we do the same with - I have had people complain that their "recap" didn't improve the sound, and after questioning admit that they ONLY did the caps, and NOT the recommended transistors at the same time. Then under my direction they did the transistors too, and came back singing praises for the increased sound quality.

Thank you so much! I will be looking into replacing all the caps and transistors that I can find around these forums. I've found a few posts already about these units so I can't wait to get started. Thanks again, I really appreciate you taking the time to help me out. I will be getting a soldering station soon so any advice on those would be appreciated as well.

I echo MTF's remarks. I have rebuilt quite a few of the SX-X3X and SX-1010 receivers and without exception recapping only provided marginal improvement (assuming one or more caps were not shorted). The real improvement came with replacing all troublesome transistors. Search AK. All the info is here! Pay attention to Mark's posts; they are the bible on anything vintage Pioneer. There are another handful of gurus here also; you will thank them all when you start the vintage bug. Without them I would never have even had a chance! Good luck! Welcome to AK.

I definitely will and I think I have the vintage bug lol.

I think what you paid is totally reasonable for a unit of this build-quality. These are nice enough to be keepers when restored.

Thank you, and I am pretty sure I will keep this for a while at least. The marantz units are my favorite look-wise but they are a little much for my first experience. I don't want to spend too much money if I screw something up soldering, etc.

 

[trump]

they wouldn't do what you are seeing - it probably needs a tuner alignment. That will regain lost sensitivity.
need special plastic tools and usually special signal generating equipment.And skills that are becoming a lost art.

Sorry for double posting but are you saying replacing all the caps and transistors probably won't fix the poor reception? It doesn't sound like I would be capable of doing a tuner alignment. Thanks again!

 

[markthefixer]

Apartment, in what city / state?

 

[trump]

Apartment, in what city / state?

Plymouth, Massachusetts. I was wondering, should I get an external antenna? I don't have the ability to put one outside but it might get a better signal? Not sure if that's the issue or not.

I also followed the guide on AK about cleaning tuners and it didn't seem to make a difference (http://www.audiokarma.org/forums/index.php?threads/how-to-clean-a-tuner-analog.144163/)

Also, I have attached more close up pictures of the tuner areas