Sansui Frequently asked, and more...

Discussion in 'Exclusively Sansui' started by Morden2004, Feb 1, 2006.

  1. Morden2004

    Morden2004 Relaxin'

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    This thread will be a [F]requently [A]sked [Q]uestions repository of information everyone wants to read. As time goes by, I'll be adding links here to (mostly) Exclusively Sansui threads where questions of great importance are answered.

    If you find a thread that you think is worthy of being in our FAQ, just PM me with the link and I'll check it out.

    And, BTW, private messaging any AK member is easy if you are reading one of their messages! Just click on the screen (AK) name at the top left of the message and select [Send Private Message].

    Paul

    Moderator - Exclusively Sansui forum
     
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  2. Morden2004

    Morden2004 Relaxin'

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    The Exclusively Sansui FAQ List


    <Keep going down - more FAQ's on subsequent messages>
     
    Last edited: May 26, 2007
  3. Morden2004

    Morden2004 Relaxin'

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    FAQ #11: Re-wiring the lights on a 8080/9090

    Lights out in an 8080/9090? Here is a repair tip that will remove the light circuit from the selector switch which often fails.

    "With the top cover removed, looking down on the right side, there is a pc board about 4" x 5 " that the selector switch is mounted on. On that board there are connection plugs. Second from the right there is a connector with a orange, grey, black and red wire attached. There is an open location on that connector. Move the red wire(~6.5 vac) from the end position to the vacant position next to the black wire. This new position will tap into the 6.5 vac supply that the source selector uses. Now the tuning lights will be on all the time and the orange source lights will switch on and off as the function selector changes(am,fm,phono,aux,dolby fm)

    [​IMG]

    More FAQ's below. Keep going!
     
    Last edited: Mar 16, 2006
  4. Morden2004

    Morden2004 Relaxin'

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    FAQ's 12 - 99

    • FAQ 12
      How do I sell my surplus gear here on AudioKarma?
      Subscribe, then use the Bartertown forum.
    • FAQ 13
      Where can I get replacement lamps for my classic Sansui? (Part 2)
      AudioKarma member Dave Wojo (dgwojo) has a great site for ordering bulbs. Click this link: dgwojo
      AudioKarma member Denis (dhenryp) also sells lamps for classic Sansui gear. Check out eBay member ID 'dhenryp' on eBay

      or contact either member using AudioKarma email.
    • FAQ 14
      I have heard about the problems with glue on component boards. How do I get rid of it?
      Click the link below.
      Sansui glue
    <More FAQ's soon>
     
    Last edited: Feb 3, 2008
  5. Morden2004

    Morden2004 Relaxin'

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    Faq 15

    • FAQ 15: How do I tell what year my Sansui equipment was manufactured?

    Easy! The serial numbers on most Sansui equipment follows a standard;

    FF Y MM ####

    where FF = a Factory Assembly Line number
    Y = last digit of the year of manufacture (you need to know the first year a unit was built - see the Sansui Database reports)
    MM = the month of build where 01 = January and 12 = December

    The remaining 3 or 4 digits are sequentially applied on the line in sequence.

    Example:

    AU-999 Serial Number is: 222010985

    Manufacturing line #: 22
    Year: 1972 (first year for the AU-999 was 1969)
    Month: January
    Serial component: 0985
     
    Last edited: Jul 3, 2006
  6. Morden2004

    Morden2004 Relaxin'

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    FAQ 16 - xx

    • FAQ 16: What does the Connected/Separated switch on my Sansui xxxx do?

      Read this excellent explanation by our very own EchoWars here .

    • FAQ 17: What is a 'Poor Mans Variac' and how do I build one?
      Read this thread for an explanation of the PMV here .


    And here are the construction pictures of my PMV. I think these are self-explanatory.
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Oct 29, 2007
  7. LBPete

    LBPete Rolling Along Subscriber

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    Dial Face Refinishing

    Many Sansui and other brands used clear Acrylic for the “glass” on receiver and tuner dials. Acrylic is great for this purpose but can be scratched. Fortunately, Acrylic is an easily “worked” material and most scratches can be polished out. Sansui back painted the lettering on these dial faces so the exterior surface can be buffed without risk of damaging the lettering. Here is the faceplate from a 9090DB with several fairly deep scratches.

    The process takes a little time but is well worth the effort. For deep scratches like these It’s best to remove the acrylic from the faceplate. That way you don’t have to worry about accidentally damaging the finish on the faceplate itself.

    The bezel is held on with screws and the acrylic is held in place with double sided tape. Try to keep the tape adhered to the faceplate as you pull the acrylic away. Also be careful not to tear the tape. You can usually reuse it. As a side note, I’ve seen a number of posts where people mention that this bezel is plastic. It’s definitely metal, probably a zinc alloy commonly called pot metal.
     

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  8. LBPete

    LBPete Rolling Along Subscriber

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    Wet Sanding

    Scratches are cuts into the acrylic. You can’t actually remove the scratch but you can remove the material around the scratch with sandpaper to lower the surrounding area to the depth of the scratch. Usually 400 grit wet/dry paper is a good place to start. If the scratches are very deep, try starting with 320 grit. The courser the sandpaper you use, the more work it will take to clean it up later.

    Keep a tub of water handy and back the sandpaper with some dense foam. Wet sand the area around the scratches until you can no longer see them. Keep the sandpaper wet while you do this.

    Repeat the process with 600 grit and then finish it off with 1200 grit widening the area. This will remove the fine scratches from the coarser sand paper.
     

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  9. LBPete

    LBPete Rolling Along Subscriber

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    Buffing

    Next comes the buffing wheel. It is a cloth wheel. These can be mounted in a conventional drill but it’s a lot easier if you have a drill press. They can also be mounted in a dedicated motor like a bench grinder.

    The cloth wheel actually heats up the surface of the acrylic with friction. You need to keep the acrylic moving or it can overheat and scuff. This takes a little time. To speed the process a compound like tripoli can be rubbed on the wheel. This increases the “cutting” action. Don’t over do it or you can scuff up the surface rather than polish it. Also in some cases, it may be necessary to retouch the area with the 1200 grit sand paper if there are a lot of light scratches left over from the coarser grits.
     

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  10. LBPete

    LBPete Rolling Along Subscriber

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    Clean and Scratch Free

    When done, the Acrylic is bright, very shiny and scratch free.

    The aluminum of the faceplate is polished with a metal polish like Semichrome polish.

    And the finished product is ready to rock.

    - Pete
     

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  11. kcollins4

    kcollins4 Rocking somewhere

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    Really nice work there Pete!
     
  12. alexkerhead

    alexkerhead To High For Infinity

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    Thanks for the guide Pete!
     
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  13. ZebraBlvd

    ZebraBlvd AK Subscriber Subscriber

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    Very nice work Pete. Thanks for taking the time to post this polishing process. I for one will greatly benefit from it.
     
  14. influx

    influx Electronica Rehabilitatus Subscriber

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    I and my G8000 thank you!
     
  15. LBPete

    LBPete Rolling Along Subscriber

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    Dolby Board Overhaul

    The unique feature of the 9090DB and it’s little brother, the 8080DB is their ability to encode Dolby noise reduction. Dolby was very new in 1977 when these units were introduced. Most tape decks didn’t have it. So Sansui provided circuitry in these receivers to allow it to add Dolby noise reduction through the tape output. These units can also receive and decode Dolby FM, a stillborn format. To calibrate the Dolby level, a test tone is built in.

    Checking this tone is a simple test of the Dolby board. When activated by pushing the Meter cal/tone switch and choosing Rec 1 or 2 on the Dolby switch, you should hear a 1,000 Hz tone from both channels. In this mode the power meters are used for Dolby Calibration. In this test they should both come up to mid range.

    The heart of the Dolby board is a 5 gang rotary switch. Like all switches in this vintage equipment, it is prone to oxidation. Since all audio signals must pass through this switch, it can cause symptoms like dropped or distorted channels.

    The Dolby circuit board was very high tech in its day. I was one of the first PC boards used by Sansui to have circuit traces on both sides of the board. To connect circuits from one side of the board to the other, they pass trough holes in the board that are filled with solder. There are 64 pass throughs on the Dolby board. The electrical conductivity of these “pass throughs” can fail causing dropped or distorted channels and or failure of one or more of the Dolby functions.

    At some point in the production of these models, Sansui recognized the shortcomings of the pass throughs and installed rivets in them. Boards with these rivets should be much less prone to pass through failure.

    The Dolby board is wired to a gang of push switches. There are a total of 36 wires that run from the Dolby Board to the push switch assembly. Early production models used another “high tech” innovation of the day, flexible PC boards to connect the Dolby board to the push switch assembly. These flex PC boards get very brittle over time and have a tendency to tear. If that occurs they cannot be repaired and must be replaced. Sansui identified this problem too. In latter production units, the flex PC boards were replaced by Ribbon cable.

    The picture below are mid and late production Dolby and push switch boards. Both of these boards have riveted pass throughs. The mid production board has the Flex PC board and the late production board has the ribbon cable.
     

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  16. LBPete

    LBPete Rolling Along Subscriber

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    I’ve been restoring an 8080DB. The unit had typical Dolby problems. The test tone, Dolby meter and Dolby FM only worked on the right side. Thoroughly cleaning the Dolby and push switches did not bring it back. The problem was likely caused by faulty pass throughs.

    An overhaul of the Dolby board is a daunting task, not to be taken lightly. Hundreds of solder joints need to be redone. There is a lot of opportunity for error.

    The overhaul has 4 stages.

     Fix the pass throughs,
     Service the Dolby and push switches
     Replace the flex PC boards
     Replace all the electrolytic capacitors.

    To do this work you need to have a desoldering iron. I use an $11 Radio Shack desoldering iron. It works like magic. It is also a good idea to have an adjustable soldering iron. It allows you to turn the heat up or down as needed. I use a Weller WLC 100. It’s also helpful to have a digital camera handy to take pictures of component and wire locations.

    Since the flex PC boards are going to be replaced, unsolder them from the Dolby board first. This will make it a lot easier to remove the board. The push switch assembly can stay in place for the time being. Be sure to make note of the position of the yellow and black wire that need to be unsoldered from the Dolby board to remove it.
     

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  17. LBPete

    LBPete Rolling Along Subscriber

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    The easiest way to get the Dolby and Push switch boards out of the chassis, is to remove the four screws that hold the front rail of the chassis and separate it slightly from the side rails. This give you more room to pull the boards out.

    There are a number of pass troughs under the Dolby switch. To get to them, the switch should be removed. Here is the switch being unsoldered. Make note of the position of the 4 small capacitors. You will reinstall them later. (As a side note CDFixer mentioned that these caps were eliminated in later production so it may not be necessary to reinstall them.)

    About halfway through removing this switch my hand started cramping up from working the vacuum bulb on the cheapy desoldering iron.

    It’s a lot easier to clean the switch when it is sitting on the bench. You can use a contact cleaner on it and then follow up with Deoxit and Pro gold. Be very careful to clean all the solder pads. Residue from Deoxit might cause solder not to bond properly when you solder it back in.

    Also be sure to clean the push switches. Line up the application straw on the Deoxit can with the last hole in the top of the push switch. Hold it flush against the hole and spray. This should force the cleaner into the switch. Then work the switches at least 10 times. Move the straw to the first hole and spray again. Cycle the switches again. The red arrows point to the holes.
     

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  18. LBPete

    LBPete Rolling Along Subscriber

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    With the Dolby switch off the board, you can see how complex the circuit is on this board. The screen printing on the top side shows the traces on the opposite side of the board. You can also clearly see the green electrical traces on this side of the board.

    The best way to permanently improve the conductivity of the pass throughs is to insert a wire into the hole and solder it on both sides. But before you can do that, you need to remove the old solder. Here is the board with the solder cleaned out of many of the pass throughs. You can see the rivets in the holes. There are also pass through peppered in with all the components on the right side of the board. You need to look very carefully to find them all.

    Once the solder is cleaned off of all the pass throughs, it’s time to start pinning. The cut leads from electrolytic capacitors make great stock for the pins. These leads are tinned to make soldering easy. Bend the lead over on both sides. Many of the pass troughs are in tight quarters so be very careful that the bent over leads don’t contact adjacent components or traces.

    Solder each pin on both sides of the board. When heated with the soldering iron, the rivets help the solder to flow freely to the other side.

    Next it’s time to replace the electrolytic caps. There are about 25 of them on this little board. Do them one at a time so you match the polarity when you install them. Here’s the board with a set of fresh Panasonic FCs. They are a lot smaller than the originals.
     

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  19. LBPete

    LBPete Rolling Along Subscriber

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    Next the Dolby switch can be reinstalled. Pay attention to the location of the little caps that were removed earlier.

    Before installing the new ribbon cable, the flex PC board must be removed from the push switch assembly. Be very careful when unsoldering the flex PC board from the push switch. The solder pads are tiny and lift very easily. Be sure to get all the solder off the pins before trying to pull them out of the board. Several of them lifted when I was taking this one off. After installing the ribbon cable, I reinforced them by running a wire parallel from the cable to a solder point down stream.

    Now the new ribbon cable can be installed. It is available from Digikey. Get the 4 inch 10 strand jumpers. The part number is WM10-04A-ND. These jumpers are a perfect replacement for the flex PC boards. The wires have the same spacing as the holes in the board and the 4” length is a perfect fit.

    I made the mistake of installing the ribbon cable into the Dolby switch first. It is better to install it into the push switch first. That way you don’t have to juggle the whole Dolby board when soldering to the push switch board.
     

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  20. LBPete

    LBPete Rolling Along Subscriber

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    OK everything back in place. Time to check it out. The good news was nothing smoked when I turned it on. The bad news was now I had major distortion on the left channel in the test tone and in Dolby FM. The meter on that side wasn’t working either. After all this work, I had made it worse than it was. Shit.

    Well I screwed around with it on and off for a few days and didn’t get anywhere. Trying to trace the circuit in the manual and transfer that to the actual board is an exercise in futility. So I went to plan B. I invited CDFixer over for lunch.

    I knew his week spot. All I had to do was flip on the scope and he just jumped right in. I don’t think there is anyone on the planet that knows the Dolby board better then Jim. He is able to trace the circuit through the Dolby switch and in short order he found the first problem. Despite meticulous care in soldering the pass through, I had created this solder bridge that had shorted one the leads to the Dolby chip.

    With the solder cleaned up, the Dolby FM and test tone were working normally but the meter still wasn’t functioning. Jim dove back in and traced it to one of the back up jumpers I had installed on the push switch board. I must have been cross-eyed when I put it in because I connected it to the wrong point. Two problems down.

    To me it was working and sounding good but Jim spotted a little surge in the meter when the tone switch was pushed. A little work with a volt meter and the schematic and he discovered a cap installed backwards. Hmmm, wonder who did that?

    Well its working great now and I got to watch a master work his craft. It was a humbling experience. The man knows his stuff.

    I hope this overview is helpful.

    - Pete
     

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