Just got a Au x1 and of coarse need info

Discussion in 'Exclusively Sansui' started by Bigdrive, Aug 5, 2017.

  1. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    Here is the before and after for the rca plugs at the back. Mine were not very corroded and I don't have any corroded ones to try but here you are. Not nearly are dramatic as the wafers. image.jpeg before and
     

     

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  2. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    After image.jpeg
     
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  3. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    Here is a better shot of before image.jpeg
     
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  4. Bigdrive

    Bigdrive Member

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    98
    Location:
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    It seemed to work great for extreme oxidization and not so good for corrosion or left over polish ( a trick from Harold). I was amazed at what it did on the wafers and I am sure it will do the same for selectors.
     
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  5. Ronito6

    Ronito6 Super Member

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    Sweet. I'll need to pick up an ultrasonic cleaner sometime soon.
     
  6. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    Here is the speaker selector. I played with the times a little and the concentrations image.jpeg before image.jpeg after. There was no mechanical means to remove the oxidization other then the ultrasonic cleaner. While it was tempting to use something no matter what that would affect the surface, which defeats the whole purpose. I think it turned out great. I was surprised on how oxidized it was and three pitting marks under the contacts.
     

     

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  7. Ronito6

    Ronito6 Super Member

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    Looks real good.

    BTW: One of these sliced to fit between the rails works great to clean switch rails.
    [​IMG]

    Mind the slider contacts. Some have 2 contact points, the others have 3.
    Make sure they go on the correct plunger.
     
  8. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    Oh I forgot about the "old eraser trick" that would have been great to try. Thanks for the warning on the contacts.
     
  9. Bigdrive

    Bigdrive Member

    Messages:
    98
    Location:
    Kelowna
    I want to check this amp for stability and DrAudio stability check says once you do the square wave and everything is OK hang a .1uf at the output.

    Just so that I am sure....do the square wave test 1 volt P to P, is this output of the generator or output of the amp? Power off, put a .1uf across the red and black speaker binding posts. Power up and check for ringing on the scope. He never says what volume or more precisely voltage to take the square wave to. Do I assume its to just before clipping or is it just a reference voltage you use for the test, say 12v or is it the 1v he speaks of at the beginning.

    Other info you may need. My scope is analogue so is it going to pick up this ringing? I have done the sine wave sweep from 1000-25000 and no voltage increase as I went up and everything looked OK.

    My final newby question of the night is what will the ringing look like?

    Cheers,
     
  10. Harolda

    Harolda Active Member

    Messages:
    431
    Location:
    Netherlands
    I have been working on and listening to the phono stages for some time and i think i am almost there.
    MM is as quiet as can be, bias is stable between 0-1mV on both channels after the Kuehne modification
    On the MC, bias also very stable between 0-1mV, but i have two conditions:
    1) When the input is used (so rca connectors plugged in) then i have a slight hum.
    2) When the input is not used i get a large hum. I found out that is caused by the self shorting RCA connectors. This is probably caused by the bad contact in the connectors due to corrosion.

    I therefore decided to replace the original RCA connectors with now ones. I also will have a closer look at the PCB connectors.

    Please let me know your experience on the MC input.
     
  11. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Location:
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    I think that means the output of the amplifier.
    No, absolutely not just before clipping - keep the output voltage of the amplifier low. Square waves are a severe test of an amplifier, but can be very revealing if used carefully, i.e. at low levels.
    Yes it will.
    Sounds good.
    It will look like a (very likely) distorted sine wave scrunched up at the rising and/or falling edges of the square wave - like a damped oscillation. A small amount of 'overshoot' is OK as long as there is no ringing. Anything that looks like 'blisters' or 'bubbles', or 'grass' on the square wave should be regarded as signs of instability or parasitic oscillation.

    I am sorry I haven't seen this and replied sooner.

    For final clarification, it would be best to check with the 'Doc' on these points - it is his test routine after all. ;)
     
    Last edited: Apr 10, 2018
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  12. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Hi Harold!

    I just checked my X1 - and I get zero hum from the Phono 1 input (with an MM cartridge connected) just a little 'hiss' at maximum volume.

    With MC input selected on Phono 1 (again with an MM cartridge connected) I get a bit more 'hiss' but no hum.

    If I select MC Phono 2 (not connected to anything) - I do get a noticeable hum - but that is with nothing plugged in, and at maximum volume.

    I hope this helps.
     
  13. Harolda

    Harolda Active Member

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    431
    Location:
    Netherlands
    Hi John,

    than i have more or less the same (i think). Do you still have the original RCA connectors or did you replace them?
     
  14. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I still have the originals fitted, fitting replacements would mean discarding the connection PCB's I think, and a new wiring arrangement would need to be devised - which is why I am reluctant to do this. Of course, if some brave soul wants to blaze the path on this one I am all ears (and eyes) ;) - however, brave or not, it may turn out to be me. :yikes:

    The AU-X11 I am currently working on has some quite badly corroded RCA's - so I am still thinking about what to do (if anything) about it. Unfortunately they haven't responded as well to the cleaning treatment that worked so well on a BA-F1 I recently restored.

    I am a bit concerned about the X1/X11 rear panel RCA socket hole spacing (15mm) and the overall diameter of new insulated (single hole) RCA sockets. :idea:
     
    Last edited: Apr 9, 2018
  15. Harolda

    Harolda Active Member

    Messages:
    431
    Location:
    Netherlands
    Hi John,

    i will give it a try, shouldn´t be too difficult. The most work is resolder all those small cables to the seperate sockets. You can use the existing wiring, unsolder the wires from the connection pcb and solder them to the new sockets.

    - The cut-outs in the panel are 11mm, so that fit's perfect to most RCA sockets. The Rean-Neutrik RCA sockets require minimal 10mm for the isolating washer to fit.
    - Most RCA's have ~16mm plastic washers, so for the washer to fit, one has to modifiy them a bit, which shouldn't be to hard on the washer. The Rean-Neutrik RCA's have a 15.5mm washer and on the AU-X1 I measure close to 15.5mm (center-to-center in horizontal direction).

    I first had a look at CMC RCA sockets, but they are expensive vs the Rean-Nuetrik and the latter seem to be of good quality.

    I cleaned the rca on the AU-X1 some time ago and that removed all oxidation on the outside of the sockets, but not on the inside.
     
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  16. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Yep, those were the ones that I liked, I can see from the measurements you mention that it wouldn't be too difficult to do. ;)
     

     

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  17. Bigdrive

    Bigdrive Member

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    Location:
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    I have the rean- nuetrik and is ready to go in. The isolation washer can be dealt easily, especially if putting the keyed one on the inside and non keyed on the outside. The only reason mine is not done yet is my speaker binding posts for B output are coming from china and it's been two months. When replacing rca I was not going to rewire which will restrict pulling back the back chassis panel once done.

    I also bought gold plated external jumpers to provide shorting. Harold, maybe that might reduce your humming if you think the jumper is corroded. Also if it's oxidization perhaps ultra sonic cleaning, since the plugs on yours look in good shape. It would be a lot of work but you would retain the original look. Also if I did it that way I would install a jumper so the ultra sonic cleaner can work on the exposed surface.

    Wow, did I ever overdo it with the square wave. I put 1v p to p on the generator and took amp up to about 8 v and swept it as fast as possible to about 16k from 1k. Everything looked ok so since the sweep on the sine wave was ok, I called it good. Power is back, and gets 162 watts verses the 152 I was getting.

    My phono is the same as Johns on MM. I have not tried any testing with MC as I don't have that cartridge.

    Cheers
    Gord
     
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  18. JoseHH

    JoseHH Member

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    I had the same doubts when I was about to do these tests on my AU-D907. I even did these tests at too high power. But please do not repeat what I did because it may damage the amplifier. What I learned is that one must set the signal generator to output a square waveform with a small amplitude such that when you feed this signal to the input of the power amplifier you get about 1 Volt amplitude at the speaker terminals. Also the unit must be powered at full mains, and not via a dim bulb tester.
     
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  19. Ronito6

    Ronito6 Super Member

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    1,087
    [​IMG]
     
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