Sansui AU-X11 Restoration

Discussion in 'Exclusively Sansui' started by SanthoshA, Sep 21, 2017.

  1. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    Can you confirm that the headphone outputs do not work when you have speaker's selected say to either A/B/A+B and it only works when the speaker selector is set to zero ?
    Going by the schematics of the X11, it looks like the headphone relay is activated always irrespective of speaker selector position, but then i can be wrong.

    This is what i can make out from the schematics:

    upload_2018-2-27_12-35-25.png



    The red line denotes a positive 23volts supply with the path considered when speaker selector is set to A, whereas the black is a reference to ground, it still energizes the relay for headphones out no matter what speaker selector is set.

    Basically the ground of all three relays ( one for speaker A, one for speaker B and the headphone relay are tied together).
    The positive supply going into the selector board, is always sent to the headphone relay irrespective of what position the speaker selector is set to, so the relay is energized as long as the amp is running ?
    The only sole purpose of a relay in chain like this, can be to cut off the headphone output in case a dc voltage is present in the output, otherwise the connection is maintained always, just passes through the headphone output, as long as the amp is running.
    Probably if a DC supply is present, we will not have 23volts activating the reed relay,cutting off supply to headphone jack, in other cases it remains on as long as the amp is powered on.

    Can you please confirm my understanding ?

    Or is is possible to verify this in case you have your X1, on the bench, i will ask some of my friends to check if the headphone out works when the speaker selector knobs are changed, in their X11, but i dont know how long it is going to take.
     
    Last edited: Feb 27, 2018
    Ronito6 and AFK81 like this.

     

    Please register to disable this ad.

  2. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    Yep, I am pretty sure you are correct, I only mentioned switching the speaker switch to position '1' as this cuts off the speakers and supplies signal to the headphones only - the most likely mode of operation.

    It would be a good idea to confirm the operation of the relay by checking TR606 turns on and pulls one side of the headphone relay coil to ground. And if it does that, check if the contacts actually close by measuring across them when TR606 turns on. It would be nice to confirm the exact fault with the relay 'open coil' or 'faulty contacts'.
     
    Last edited: Feb 28, 2018
    Ronito6 and SanthoshA like this.
  3. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    I have confirmed the TR606 is fine, and have ordered a replacement relay, the sad part is that the power supply board needs to be removed again, luckily most of the wires are plug and play.
    Will keep you posted on the updates.
    Thanks for your inputs Hyperion !
     
    Ronito6 and Hyperion like this.
  4. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    I have started working on the flat amp board, while waiting for the reed relay to arrive.

    In order to remove the flat amp board completely from the front panel, i had to de-solder 4 wires pictured below.
    All desolder joints are boxed in Yellow.
    IMG-6389.JPG
    IMG-6390.JPG

    And finally the last two wires (Grey and Blue) from the Buffer Amp board.
    unnamed (2).jpg

    Removed Flat Amp(F-3455):
    unnamed (3).jpg

    I managed to a quick recap, and also moved the small capacitor clinging in the bottom to the top of the flat amp board.
    I will inspect to see if the power amp level gain knobs are touching the capacitor legs, when re-mounting it back.
    The Nippon Chemicon bipolar's were also replaced with Nichicon Muse.
    unnamed (4).jpg

    In order to complete my restoration on the Flat Amp i need couple of inputs from fellow seniors:
    1. One of the Polystrene cap looks damaged, but i am not sure unless any of you can confirm.
    unnamed (6).jpg
    The sides of the Polystyrene Capacitor looks ok though.

    2. Which model potentiometer's were used for the flat amp board, since the adjustment is from the bottom of the board, in a upside down fashion, looking for options that can be considered.

    3. I found two black flag capacitors in the Flat Amp amp board wired in series to another capacitor, and the end of the capacitors leg was soldered in the PCB.
    Not sure, why these capacitors were wired in series, probably for handling better voltage, but this also decreases the capacitance i believe.
    Any comments on this approach, please do let me know your inputs.

    The marking on the small capacitors in series says 8D CD or it's BD CD i am not able to make out what value in picco farads is the small capacitor that is wired to the black flags in series.
    unnamed (7).jpg

    I plan to replace them with Ceramic Disk Capacitor C0G/NP0 from Vishay, as these are locally available.
    Part Number: 561R10TCCV30
    FEATURES
    • Ultra stable over temperature and voltage
    • Used when the ultimate in stability is required

    Unfortunately Murata's C0G/NP0 is not locally available, so am in a confusion choosing between the Ceramic Disk of Vishay Vs Cornell Dublier's Silver Micca.
    Please do let me know your suggestions/feedback.

    Thanks in advance for your time and support !
     
    Ronito6, Multimode and Hyperion like this.
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    It looks ok to me, it may have been caught by someone's soldering iron? if you can't see anything melted/burnt it should be OK.
    I think I might have mounted my trimmers on the underside of the board - perhaps there is a picture in my AU-X1 thread? - but I can't remember if I used 'top adjust' or 'side adjust' types.
    It looks like an attempt to 'manufacture' a lower value capacitor, If we guess at '8D' being 8pF - this makes the combination ~2pF - If it were me I would use a 3pF as a replacement. Whatever the value of the '8D' capacitor the combination must be some value less than 3pF.
    I would use ceramic replacements, as long as you use C0G/NP0 you will be fine. ;) (cheaper too :) )

    You are doing really well with this! - you are asking carefully considered questions backed up with good pictures and great information. :thumbsup:
     
    Last edited: Mar 4, 2018
    Multimode, AFK81 and SanthoshA like this.
  6. AFK81

    AFK81 New Member

    Messages:
    4
    Great Work Santhosh, the whole tread is so pleasing to the eye, simple yet tons of information.
    Love the laid back,step by step approach and the photographs -wow,it is the cherry on the cake!
    Keep it going Bro,Good Luck.
     
    Ronito6, SanthoshA and Hyperion like this.

     

    Please register to disable this ad.

  7. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    Thanks for your inspiring words of confidence, i would not have made this far without the guidance and support of fellow forums members.
    There were the ones who also contribute to the restoration work going on with the X11.
    AK is a very good forum, and i also happy for the support i have been getting from fellow members.
     
    Hyperion, Ronito6 and AFK81 like this.
  8. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    I have also removed the Regulated power supply board now, owing to get it restored as i work on the front panel PCB's.

    Board Removal Documentation:
    The Regulated Power Supply board F-3463, has its power supply inputs coming from the Power Supply and Protector circuit board F-3462(which is in-turn powered by the square transformer).
    This is where the Nichicon Dual-E capacitors come into picture, and these caps are mainly used for the Preamp's power supply filtering,as per my understanding.
    In order to remove the regulated power supply board, couple of connectors needs to be removed.
    Regulated Power Supply Removal 1.jpg
    The above marked connectors have the power supply voltages coming from regulated power supply PCB.
    Regulated Power Supply 2.jpg
    The above marked connectors in Power Supply/Protector board needs to be removed F-3462.

    Next in the Regulated Power Supply Board there are again two Molex connectors, that feed power supply to the Preamp Boards/F-3455 Left and Right Channel which had to be removed.
    Regulated Power Supply Removal 3.jpg

    Note: The Regulated Power Supply Board, is mounted vertically, and to remove it one needs to pull the board upwards, the three tabs in the PCB hold this board, in the vertical position.
    Regulated Power Supply Board 4.jpg
    The tab markings that hold these boards are boxed in Black, pulling it out is going to damage these tabs, and its best to pull this board in upward direction during removal.
     
    Hipocrates, Ronito6 and Multimode like this.
  9. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    Regulated Power Supply Board (F-3463):
    F-3463 2.jpg

    Ill-Fated Glue:
    F-3463 3.jpg

    I have a question regarding the potentiometers used on the Regulated Power Supply and i have a tough time sourcing multi turn potentiometers for the required values.
    The potentiometers required for the regulated power supply board are the following.
    1. 4.7k‎Ω X 2
    2. 2.2k‎Ω X 2

    The problem is i don't get them in actual values for the multi turn poteniometers, but i have them available in say ratings of 500 ohm's lesser or above the rated vlaues.
    But since, potentiometer's work in dividing the resistance, i am quite reluctant to deivate from rated values.
    Assuming we have a 2.2kΩ single turn potentiometer and the the potentiometer is turned 25%.
    The effective restistance between pins 1-2(0.555KΩ) and the effecitve resistance between pins 2-3 (2.2KΩ - 0.555KΩ) = (1.645KΩ)

    So deviating from the rated potentiometer value, will lead to wrong resistances across the other pins ?
    And this is applicable only when all three pins of the potentiometer's are used.

    I am quite confused/reluctant in changing the rated potentiometer's value just to have the multi turn feature, but please do let me know your inputs/suggestions also.
    I have verified that single turn potentiometers are available in 4.7k‎Ω and 2.2k‎Ω ratings.
     
    Last edited: Mar 10, 2018
    Ronito6 and AFK81 like this.
  10. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    I used multi-turn replacements when I did my AU-X1, I am pretty sure I used 2K for the 2.2K and 5K for the 4.7K. In both cases, and referring to the schematic these are used as 'variable resistors' rather than 'potentiometers'. Used as variable resistors the concern about 'in circuit' track resistance is not an issue, there is a 'padding resistor' associated with each of the trimmers in this case, (R73, R74, R33, R34) whose value could be altered slightly to compensate if needed.

    However, where you find a trimmer used as a potentiometer (like VR01 on the X1 Power Amp board), then your concerns are valid, but seldom an issue, and in the case cited this too has padding resistors R09, R10 etc to prevent excessive current flow at the extremes of adjustment. Luckily it is rare to find a 'trimmer value issue' with a trimmer used as a potentiometer, the VR01 in this case being 100Ω, an easily obtainable value whether single or multi-turn.
     
    Last edited: Mar 10, 2018
    Ronito6, SanthoshA and Overundr1 like this.
  11. Overundr1

    Overundr1 AK Subscriber Subscriber

    Messages:
    2,479
    Location:
    Mississippi
    Those original single turn trimmers would deviate farther from their stated ranges (especially as you got close to one end or the other of the adjustment range) compared to the modern Bournes replacements. It is also a good practice to measure each new trimmer before you install it, over the past few years there have been a couple of instances where the new trimmer does not track properly, will save you tearing the assembly apart again.
     
    Hyperion and SanthoshA like this.

     

    Please register to disable this ad.

  12. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    Thanks for the reply regarding the potentiometers!
    It really does clear my doubts.
    And yes I am measuring the values of new as well as old trimmers .

    When I usually replace the old timmers with new ones I usually set the new ones to the same values between pins 1 and 2 pair and the other pair 2 and 3 measured in old trim potentiometers.

    Unless there is a huge deviation I set the new trim pots to null zero position, or fully counter clock wise .
    And then remeasure voltages and calibrate the new trim pots again .

    In most of the cases I use the values from old trim pots as a reference to start with when replacing them , but I always recalibrate after installing the new trim pots. Some times the pin out diagram for the pot changes the 1,2 and 3 pins are placed in reverse .
    I just do this to be on the safer side .

    With a pot that has pin outs in reverse the results will be catostrophic is turned in wrong direction .

    Meanwhile I have managed to de-solder a couple of capacitors and remove the glue .

    E7FD214D-3446-479F-9160-C75645D7EECE.jpeg

    E7A4F415-C84C-41ED-929C-E0933D8B8DB0.jpeg
    I might as well replace this resistor with good metal films again.

    C56703B9-332A-4028-A0E3-E813A30BEFF6.jpeg
    After cleaning the glue:
    A86CC95A-0810-4F27-805E-A74E17A14C56.jpeg

    There signs of Sansui glue even underneath the PCB or is just too much flux, I am not sure but there’s a huge glob of it underneath the pcb.
    00478ED0-E309-4E9D-9B92-751E4E7033C3.jpeg

    Also strangely but more weird I would say ,one of the capacitors with Sansui glue on it measures to have 0 ESR. Is this a good sign or a bad sign .
    BD5CC0F7-68D5-4604-BE16-6CD85922719D.jpeg
    I again recalibrated the probes of the ESR meter and took a remeasurment, I still get 0.00 ohms ESR.
    The meter beeps twice indicating it is good,something fishy .

    The capacitance rating is quite good .
     
    Last edited: Mar 10, 2018
    Ronito6 and Hyperion like this.
  13. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    Yes that does look like glue - it has to go.
    Never seen that before, the Peak testers are good but quite basic, a different capacitor tester may give a different result revealing just how 'fishy'. :D

    Nice work on the glue removal by the way - very neat work. :thumbsup:
     
    Ronito6 and SanthoshA like this.
  14. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    I have to give credits to Ron as it was his advice to use Toluene and it did the magic !
    He’s been extremely helpful in supporting me for the restoration .
     
    Ronito6 and Hyperion like this.
  15. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    Ron is a real treasure - there is no doubt about that. ;)
     
    Leestereo, Ronito6 and SanthoshA like this.
  16. Ronito6

    Ronito6 Super Member

    Messages:
    1,115

     

    Please register to disable this ad.

  17. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    I am still currently held up with the Power Supply Board restoration, here are the updates:

    1. I managed to clean the whole under side of the PCB, to remove the oxidation/dirt/grime.
    Before Cleaning:
    Power Supply board.jpg
    After Cleaning:
    Power Supply Board After Cleaning.jpg

    Solder Defects Observed:
    Solder defects.JPG
    You can one solder has been completely eaten, and is hollow, and the areas where the capacitors are connected to the middle trace had nearly no contact on the components.
    There were couple of places where the component would slightly when i touch the leads.
    I have re-worked all these places, on the entire board.

    2. All 8 heat sinks were removed, transistors re-greased and mounted back to the heat sink
    Heat sink cleaning.JPG
    Heat Sink 2.JPG
    3. All the capacitors in the board are replaced with Nichicon Fine Gold and KZ equivalents.

    Desolder Joints:
    De-Soldering.jpg

    Recapped Board:
    Power Supply Recap 1.jpg
    Power Supply Recap 2.jpg

    I have also replaced the glue eaten resistor with MultiComp Metal Film, unfortunately i do not have a pic of the same, i will update it when i have some time.
     
    Ronito6 and Hyperion like this.
  18. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    The problem:
    I removed the 4 potentiometers to replace them with Bourns Multi Turn Trim Potentiometers.
    During the removal process, i noticed the wiper and the third pin are shorted just like what Hyperion has mentioned in couple of posts of back.
    And i am thankful for him in pointing it out.

    The net effective resistance(existing calibrations) are the following:
    Potentiometer 1. 0.560 kΩ (Rated 4.7 kΩ) - For Flat Amp Power Supply
    Potentiometer 2 0.560 kΩ (Rated 4.7 kΩ) - For Flat Amp Power Supply
    Potentiometer 3: 2 kΩ (Rated 2.2 kΩ) - For Phono Board Power Supply
    Potentiometer 4: 2 kΩ (Rated 2.2 kΩ) - For Phono Board Power Supply
    Potentiometer.jpg
    Note: The above measurements are taken, with care to ensure, i select the right pins when measuring as two are always shorted.
    I have even re-verified the same, as i have taken the measurements twice once prior to de-soldering and second after de-soldering the pots.


    I had also observed high heat signature on the heat sinks, used for phono board power supply, and looks like i have found out the reason.
    The potentiometers have turned fully for the phono board calibration in clock wise direction, and the amp has been running like this for i don't know how many years.
    And i also observed that the existing thermal grease was very brittle on these heat sinks, and would come off easily during the removal process.

    Lesson Learnt:
    I should have checked the potentiometers first, and then proceeded to work on the heat sinks.
    Or is should have checked for proper calibration of the amplifier before starting on the restoration work, it would have clearly given me an idea on which areas of the amplifier need more attention, or have been abused/miscalibrated over the period of use.

    Now its going to be double the effort , as i am going to remove the 8 heat sinks and test the transistors again, just to be sure all of them are in good condition.
    I can do with only the 4 that are used in the phono boards power supply section, but i just want to re-check all once again.
     
    Last edited: Mar 30, 2018
    AFK81, Ronito6 and Hyperion like this.
  19. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    44,620
    Location:
    Hertfordshire, UK
    This is what I found on my X1 - (but I had adjusted all the trimmers first, to check for things like this :)) - and was unable to achieve the 11V output for the MC head amp supplies with it like this. I tweaked the value of the track padding resistors, to bring the pot track resistance within the range of adjustment for 11V - worked a treat. ;) I did describe this in my X1 thread IIRC.
     
    Ronito6 and SanthoshA like this.
  20. SanthoshA

    SanthoshA Active Member

    Messages:
    128
    Spot on !
    You nailed it, the voltage stays at 10.5V and never fails to increase beyond this value, it should actually be 11volts.

    I have read your restoration posts(hyperlinked for reference) and will do the necessary corrections to the padding resistors, for now i did a test run, replaced all trim pots to Bourns Multi Turn in the Regulated Power Supply board and also the Flat Amp(i have mounted the multi turns on the bottom of the pcb, this took some effort, but it is easily adjustable from the top of the front panel).

    I do not have the specific resistor values for the padding resistors and have packed the front panel for now, the lack of 0.5volts will be addressed as soon as i get the resistors.

    I believe this particular issue is a flaw in design may be, i also read the posts regarding grounding issues that cause this.
    But i am pretty sure the grounding is fine/perfect in mine.
     
    Ronito6 likes this.

Share This Page