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SX-990 Recapping help.

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Dakota Clark

New Member
This is my first post so I am sorry if I am in the wrong area. I am looking for the caps or a whole cap kit to revitalize my SX-990 that has been sitting in a closet for many years. I have looked online and have found nothing really for the 990 other then replacement boards, knobs, and the like. Any help guiding me in the right direction would be greatly appreciated.
 
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Welcome to Audiokarma!
You are in the right place for a Pioneer SX-990.
Do you have any electronics experience? Any tools, like a DMM, soldering iron and DBT?
For first power up of a unit that has been sitting around with unknown issues you need a Dim Bulb Tester: Dim Bulb Tester diagram pictorial... please feel free to copy and post.
Get a decent DMM (meter), and a decent soldering iron.
Download the free Service Manual from hifiengine.com: HiFiE
If you have never worked on electronics before go to a thrift store and get an old unit to practice soldering and unsoldering.
 
Great project!
Lets see a picture of it.

Do you have your service manual yet?

Also, what are the part numbers of the internal boards? (Sometimes there are running changes, and the PN's of the boards track that.
Example; There are 2 versions of the critical protection board for the last receiver I started a restoration on AND doing a part for part inspection, I see differances from the published Service Manual.

:)

Best of luck, and get that Dim Bulb Tester ready!!
 
For the SX-990 repair probably right place. You can go over to introductions and start a thread saying hi and if you want you can introduce and describe yourself. You can look at past introductions to get an idea.

Welcome to AK. Restored the next model up the line, the SX-1500TD. I think a number of boards are common between the two but the 1500TD has a more powerful amp section. Very nice sounding receiver after restoration. You may have to build your own cap list. As far as specific caps you will get a variety of opinions. Some go for the audio grade caps some go for the more general purpose ones.

If you are new to this there is a lot to learn. You want to practice some to wrap your head around things and become competent so you don't make a mess of a unit you really value. There are many failed attempts on the site. Especially solder techniques making good solder joints and learning how to not tear up solder pads. Acquiring some basic cheap testers and a good voltmeter are valuable and help cutting down mistakes like putting putting replacement transistors in the wrong orientation and figuring out bad components. Also learn about DeOxit and other cleaners and how to clean contact, pots, switches etc. Sometimes control cleaning alone can bring a unit back to life.

People may knock the old cap-coupled designs but I like this one. This old Pioneer line (SX-440, 770, 990, 1500TD, not so common 2500) has a number of fans. The bottom two have black faces the other ones styled like the SX-990.

I did an internal accounting board by board, upping the voltages at least one standard level and the lowest voltage guys just used 25V minimum. Mostly Nichicon UPW, Wima MKS2 film caps for 3.3 uF and below, the Nichicon Gold Tune (LKG) for the output caps. Also replaced a number of transistors. Some of the old transistors have reliability/noise issues. The fix and repair one I restored had a blown up amp channel one on one side (fuse blew) and other channel was just spewing noise. Working great now.

You often need to do an accounting of what was actually put into a unit. What is in the service manual while mostly accurate what actually comes off the manufacturing line may have a number of changes. Things get added, others removed, values and voltages of caps and semiconductors used may change. Some board designs may change.

And a dim bulb tester with proper wattage incandescent light bulb can be your friend. Can keep you from blowing things up. Especially after you were inside one working on it and did something wrong. If the bulb glows brightly you then have to find the error. Can be good to do the work in stages, maybe board by board checking its operation between each stage.
 
I have a downloaded copy of the manual. I am reading through the reply's when I have free time and trying to get a list of what I need. I'll upload pictures probably on Saturday 7-9 EST. I'll also reply with the internal board number. Thank you for a warm welcome.
 
dly66 said:
For the SX-990 repair probably right place. You can go over to introductions and start a thread saying hi and if you want you can introduce and describe yourself. You can look at past introductions to get an idea.

Welcome to AK. Restored the next model up the line, the SX-1500TD. I think a number of boards are common between the two but the 1500TD has a more powerful amp section. Very nice sounding receiver after restoration. You may have to build your own cap list. As far as specific caps you will get a variety of opinions. Some go for the audio grade caps some go for the more general purpose ones.

If you are new to this there is a lot to learn. You want to practice some to wrap your head around things and become competent so you don't make a mess of a unit you really value. There are many failed attempts on the site. Especially solder techniques making good solder joints and learning how to not tear up solder pads. Acquiring some basic cheap testers and a good voltmeter are valuable and help cutting down mistakes like putting putting replacement transistors in the wrong orientation and figuring out bad components. Also learn about DeOxit and other cleaners and how to clean contact, pots, switches etc. Sometimes control cleaning alone can bring a unit back to life.

People may knock the old cap-coupled designs but I like this one. This old Pioneer line (SX-440, 770, 990, 1500TD, not so common 2500) has a number of fans. The bottom two have black faces the other ones styled like the SX-990.

I did an internal accounting board by board, upping the voltages at least one standard level and the lowest voltage guys just used 25V minimum. Mostly Nichicon UPW, Wima MKS2 film caps for 3.3 uF and below, the Nichicon Gold Tune (LKG) for the output caps. Also replaced a number of transistors. Some of the old transistors have reliability/noise issues. The fix and repair one I restored had a blown up amp channel one on one side (fuse blew) and other channel was just spewing noise. Working great now.

You often need to do an accounting of what was actually put into a unit. What is in the service manual while mostly accurate what actually comes off the manufacturing line may have a number of changes. Things get added, others removed, values and voltages of caps and semiconductors used may change. Some board designs may change.

And a dim bulb tester with proper wattage incandescent light bulb can be your friend. Can keep you from blowing things up. Especially after you were inside one working on it and did something wrong. If the bulb glows brightly you then have to find the error. Can be good to do the work in stages, maybe board by board checking its operation between each stage.
Click to expand...


Wow! Thank you for all the information. I have restored Reel-to-reel players but never have done a recapping. This seems like it may be a large learning curve and I appreciate the help.
 
merlynski said:
Welcome to Audiokarma!
You are in the right place for a Pioneer SX-990.
Do you have any electronics experience? Any tools, like a DMM, soldering iron and DBT?
For first power up of a unit that has been sitting around with unknown issues you need a Dim Bulb Tester: Dim Bulb Tester diagram pictorial... please feel free to copy and post.
Get a decent DMM (meter), and a decent soldering iron.
Download the free Service Manual from hifiengine.com: HiFiE
If you have never worked on electronics before go to a thrift store and get an old unit to practice soldering and unsoldering.
Click to expand...

I have restored 2 Teak A-4010s RTR players only had to do soldering on some chewed cables (mice beat me into it.) Thank you for the reply and the tips with a DBT. I never thought of that.
 
That's a cool receiver. I don't know much about those but just went and looked and I see why they are popular; I'd probably like the cap-coupled sound too!

My strategy to learn - which is ongoing :) - was to check out basic electronics books at the library, read tons of posts on here and I found an SX-434 to restore (low investment relatively speaking and pretty simple unit). Turned out to be a good chance to get used to the Pioneer SMs and the new caps and transistors improved it so much I couldn't believe it. Gave that one away and found a "for parts/not working" SX-636 with one channel out and had great luck with it too, been listening to it daily for 6 months with no issues and it's the best-sounding amp I have. I imagine that these receivers sound like they did almost 50 yrs ago when new or maybe even better, after restoring based on the lists you can find on here (thanks to all the generosity and helpful contributions over the years).

I think you'll need a good solder-sucker as well. Especially as dly mentioned, to help avoid lifting pads on the boards. That takes some technique and practice! You can fix lifted pads but it's just better to avoid it.

I'd also get a good parts list together in a spreadsheet. That can take research and sometimes parts change so you have to find a sub, often it can be the same part with a different suffix.

Good luck and post pictures!
 
Following ... I also have that receiver, and on my (long) project list.
I had found pdf’s of schematics and parts list if you need any.
 
Not sure what tools you have lurking in your tool box.
here are a few to look at:

Velleman VTDESOL3U Vacuum Desoldering Pump with Heater 30W
Tenma 21-8240 Vacuum Desoldering Iron
Hakko FR-301 Desoldering Tool

I own at least one of these.

As for the DBT, its not "Optional" in my humble opinion. Its saved my Arse 3 times on my current project. (Due to my mistakes)
Access to a 11X17 printer is a major plus. If the .PDF of the manual allows, an exploded print allows for notes and jotting any delta on transistor leg orientation. Mind that Collector location.
https://www.hifiengine.com/ Sign of, its free and I don't think it ever triggered any spam (member for over 10 years)
A tester based on the "Mega328" project is almost worth its weight in silver, costs less than a sixer. (but not a two-fur) Tests\reads values of Caps, Resistors, Diodes and Transistors. Always check them as they come out, and denote the leg orientation.

Best of luck!


 
Just as a note, desoldering equipment is very useful, but expensive. I use solderwick, with some added liquid flux to the braid. If you are wanting to get into regular repairing electronics it is a good idea, but solderwick is much cheaper.
Those little testers are available on the 'bay for cheap, especially without a case.
I definitely agree the DBT is not optional.
Here is a very useful link: So You Want To Repair Audio gear, Eh? Here's the tools you need...
The scope and the signal generator can wait, especially if you are just a hobbyist. Computers these days can do most of that.
 
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