Sansui 6500 Volume/Balance Pot

Discussion in 'Exclusively Sansui' started by surfnsound, Jan 13, 2018.

  1. surfnsound

    surfnsound Active Member

    Messages:
    113
    Hi all, need your help here. I got myself a AU-6500 but its not in good physical shape. The previous owner has exchanged volume and loudness pots, which are working now, but loudness is not working. The soldering job does not look very clean neither.

    I think I want to replace bother and redo the connections.
    1. What would be a good replacement for part 1010580, 250k? The current pots for volume and balance are both stereo with 3 tabs each. Do I need 4 tabs? What are the original connections?
    2. What are the original cable connections, colours, cable routing from the F-2036 board to the volume and balance pots?
    3. Not important but nice: The plastic covers on the on/off switches (mute, loudness, ..) as well as all buttons are in bad shape. Any source would be appreciated.
    Here is the current situation....

    Balance pot

    IMG_0330 (1).JPG

    Balance pot and volume pot en top

    IMG_0332.JPG

    I have access to the schematics but again, I can't determine the original cable routings. Any photos or explanations of the original situation would be appreciated...

    Thanks, this baby plays nice but would love to restore it to original with loudness.

    Cheers,
    David
     
    Last edited: Jan 14, 2018

     

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  2. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    Hi David,
    The 1010570 is still available from Sansui-parts. Looking at the parts list, it states both volume and Balance are the same, which I think is an error.
    Usually, for Loudness to work, the 4th tab on the volume Pot, injects the Loudness into the Volume Pot. If the Pot is round then it will be a separate tab at the opposite end of the 3 terminals.
    The Balance, could be the same, with the 4th Tab being connected in a such a way to give the balance, effect as per the diagram.
    May me another member who has worked on the 6500 can clear up on the parts you need and the colours of wires etc..
    Mano
    ps.. cant see the pics

    1010570 is the Baance
    1010580 is the Volume Pot
     
    Last edited: Jan 14, 2018
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  3. surfnsound

    surfnsound Active Member

    Messages:
    113
    Hi Mano, thanks, pics are now uploaded, always have sharing problems with google photos.

    According to the AU-6500 manual both pots are 1010580. THe 1010570 posted on Sansui parts does not have the loudness tap. I do not find a 1010580 on Sansui-parts and neither on ebay. That's why I though using new alps.. maybe with a PCB for easier soldering.
    If any of you might have a picture or two from the AU-6500 to see whether the original cables go that would help.
     

    Attached Files:

  4. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    Hi David,
    I have used the ALPS blue pot as a replacement for the Volume Pot and also to retain the Loudness function. Yes you can use a PCB or solder direct to the Alps pins and then onto the existing leads or to the F2036 board. The 1010570, I would suspect is the Japanese Balance control implementation at that time. ie.. when the Balance control is at the middle, the signal there is no resistance in the signal path. When you turn the Balance to the left, for example, the Left channel volume remains the same, while the right signal is attenuated.
    I ended up making a replacement for one of these out of dual 36 step rotary switch as these are not available new.
    If you are novice to this technology, I would wait for another members who have actually worked on the 6500 to give you further help to progress this.
     
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  5. surfnsound

    surfnsound Active Member

    Messages:
    113
    Hi Manu, thanks, I ordered the blue APLS with loudness tap for volume And another blue alps for balance (but indeed there is resistance on both sides...). In the manual the say 250k (M,N). Ordered an MN250k just in case as well.

    Now connections...

    Balance: On the schema I think I see the balance VR701 and VR70. I think I can figure out the cables based on these schematics.

    Volume: But I do not see the master VR703 and VR704, the volume. I think they just might be "in the fold" (they not on the next page neither. Hello AU-6500 owners;....Maybe somebody has another schematic? Or can make a pic of the cabling?

    vol.png
     
  6. surfnsound

    surfnsound Active Member

    Messages:
    113
    If anybody had some pics or schematics for volume and balance..... I am still searching. :)

    In the meantime if work on the esthetics, the plastics switch covers and (pieces broken off) the buttons (black colour gone) were in a very shabby state.

    Plastics switch cover: Sand, repair with epoxy, sand... and still need to spray paint shiny black

    F29FC838-F388-497F-85C5-AE58D7B3FC84.JPG IMG-0370.JPG 4DE78BC1-6DD7-4B59-B953-6C8BDBF60B8A.JPG

    Buttons: Dremel to get away colour residues, shine, spray paint.. will try two or three times. I know the original buttons have some blank metal parts, but that seemed too difficult to do, I just covered the blank metal part close to the amp. All the rest will be black.

    BE753AB3-C1A1-49C5-80E5-48BF3A53BD58.JPG 3A4D6A59-3878-4176-9807-6F8655B5A9C3.JPG
     

     

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  7. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    Hi David,
    Those switch tabs have been abused. I will look at the schematic, over the weekend and will suggest where you would need to connect the Volume and Balance pots, not difficult, just takes a bit of time to write it down accurately for you to follow
    Mano
     
  8. surfnsound

    surfnsound Active Member

    Messages:
    113
    Mano, great, that would be fantastic, thank you very much. Pots have been shipped, should get them soon. I listen to the AU-6500, fantastic, just LOVE the sound. My comparison is a SX-750 which i love as well, but the 6500 has a sound signature that I just dig. Especially also with vinyle, phono stage seems very good. I use a Sont ST-5130 as tuner and its the best FM that I ever heard. Speakers are Wharfedale Dovedale III. The 6500 is not recapped yet and already sounds perfect.

    Here are some more shots from getting the buttons and switch covers back in shape.

    Ready to get epoxy on it
    IMG_0377.JPG
    Sanded with dry epoxy
    IMG_0379.JPG
    Spray paint two layers
    IMG_0380.JPG
     
  9. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    Hi David,
    Tried to keep the diagram simple to follow.
    Will need to use low noise screened cable, if you can find miniature 4 core screened audio cable, it will make it tidy.
    If you can get the Original Balance pot, then use the Original Dual pot wiring
    Otherwise you can use a single, 500K Linear pot to do the same.

    The Blue Alps pots with loudness have 4 tabs at the bottom. The Pots are square and the 4 tags are offset as shown, There should also be a label at the back, showing how the pins are numbered.
    Pin 4 on these are the Loudness tap.

    I've marked the F2043 with the corresponding ID as used by Sansui and similarly on the Balance and Volume Pots.

    F-2045 also, shown with where you sill need to connect the sig-out from the Volume pot to.

    The G - connector on the F-2036 board can get very busy, if you use this as the common Signal Ground point.

    As I have not worked on a 6500

    Would suggest, connect the Screen from the Volume Pot to the G on F-2036, and then Fan it to the Balance Pot.

    If you use a Original type Dual Balance Pot, then the Ground/Screen is connected to opposite ends of the Left and Right pins..
    Left - 1 2 3 (Pin 1 signal In, Pin2 Sig Out, Pin3 Gnd)
    Right - 1 2 3 (Pin 1Gnd, Pin 2 Sig Out, Pin 3 Sig In)

    Alternate Single Balance Pot - 500K Linear -- Pin1 - Left Sig, Pin2 Sig Gnd, Pin 2 R Sig)

    Should be enough to get you started, all of the signal wires needs to be screened and the screen must be connected to Signal Ground at least on one end at the absolute minimum.

    The tracks on the boards are very easy to lift off, so take care.
    Simple diagram of connection included, if you want me to pm this let me know.

    [​IMG]
     
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  10. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    Forgot to mention I used the AU7500 manual to fill the gap in the middle, it uses the same set of components for the F-2045 board.
     
  11. surfnsound

    surfnsound Active Member

    Messages:
    113
    Wow, fantastic Mano !! That's exactly what I needed. I have a blue cube alps pot for balance with three connections already here and wait for the 4 connection volume blue cube alps that shipped from China. As soon as its here I start with the wiring. I poste before after pics. Hope I have good access to the board wiring points. I think the original cables have been used for the current wiring (i see the shielded cables), so I might be able to reuse them.

    Here is the update of the rework of the knobs and caps, not like original, but good enough for living room looks :)

    IMG_0390.JPG IMG_0388.JPG IMG_0391.JPG
     

    Attached Files:

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  12. _mano

    _mano Active Member

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    Location:
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    Eye catching...:beerchug:
     
  13. surfnsound

    surfnsound Active Member

    Messages:
    113
    Ok, like we wouldn't have enough work, this just happened. I got the receiver since about two weeks, phono was dead quiet and sounded fantastic.
    Since two days I hear this in phono:



    It only on phono, tuner and aux working perfectly well. I took out the phono board and cleane dthe contacts of the board, but still bad sounds. Might this be some transistors on the board?
     
  14. surfnsound

    surfnsound Active Member

    Messages:
    113
  15. _mano

    _mano Active Member

    Messages:
    441
    Location:
    London, UK
    also, check if any caps are breaking down as well.. The Phono section is very sensitive, so any scrap of electrical noise can come through,. As its both channels, check the PSU feed to these as well and the grounding is solid.
     
  16. smurfer77

    smurfer77 Super Member

    Messages:
    1,385
    Location:
    San Francisco
    I needed a similar volume pot recently (dual 250kOhm with centre taps for loudness circuit) on a Sansui AU-111. I looked at the ALPS units but I couldn't find one with a shaft long enough. Most of the Sansui units from the 60s and 70s have ~50mm shafts, where as the ALPS units seem to be around 25mm.

    Please let us know the shaft length of your original pot. If it's around 5cm you are actually in luck as the same pot (dual 250k with centre tap) was used in several Sansui models, including the Sansui AU-555A (and therefore if you check model compatibility, it's not too hard to find on the used market).
     

     

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  17. surfnsound

    surfnsound Active Member

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    @_mano Yes, will check these. If I get everything else working and in shape, I will start recap. Especially phono looks easy enough.
    @smurfer77 The pot which is in there right now is not original. Its a 3 pin with plastic shaft trimmed to have the same length as the others: 25 mm. That means the chinese Alps pot should just work. But you bring me to the idea maybe to try to find pot from another AU indeed. Like this one. But boy they cost more then my AU...:)
     
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  18. smurfer77

    smurfer77 Super Member

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    1,385
    Location:
    San Francisco
    if the shaft length on that model is 25mm I would just for for the new ALPs pots then. good luck!
     
  19. surfnsound

    surfnsound Active Member

    Messages:
    113
    @_mano it works ! I have to say that your connection plan is fully accurate, every single connection was correct and I have now a fully working AU-6500. The loudness switch also is again fully working. Only thing, my mistake, I have used a log pot for balance, so my balance is not in the middle. I will buy another lin pot to change that.

    IMG_0510.JPG IMG_0449.JPG IMG_0456.JPG IMG_0454.JPG

    On the phono card I changed the transistor to get rid of the hum:
    • 2sa726 -> KSA992FBU
    • 2sc1313 -> KSC1845FTA
    As you see on the picture, the volume pot is not made for screw on buttons. I used a little metal piece and glued it in the opening of the pot so I could screw on without deforming.

    Here is the beauty:

    unnamed.jpg

    Thanks for all your help, certainly Mano for that diagram certainly useful to anybody who needs to change the pots !!

     
  20. surfnsound

    surfnsound Active Member

    Messages:
    113
    I seem to be unable to find a 250k stereo linear pot. 100k or 500k. Does it work with either a 100k or 500k linear pot?
     

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