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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    Here is the new foot print.....better but if you look closely you can tell the contact in the middle is not great image.jpg
    Best it's going to get unless someone has an idea?
     

     

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  2. slimecity

    slimecity Super Member

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    Unless someone thinks differently, I cant see this being a big issue as the purpose of the thermal paste is to transfer heat, and this would include from areas of the trannie not quite contacting the heatsink in places? It appears that the trannies are mostly contacting the heatsink.....?
     
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  3. Bigdrive

    Bigdrive Member

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    98
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    IMG_4493.JPG Here is the first side as removed after thermal grease applied and would have been put in service. As you can see, no contact between legs
     
  4. Bigdrive

    Bigdrive Member

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    Post #63

    Trannie=transistors darn spell check
     
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Last edited: Sep 6, 2017
  6. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    +1 - I wouldn't worry too much about 2½ thou, it isn't ideal but the heatsink compound will take care of that.
     
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  7. Bigdrive

    Bigdrive Member

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    IMG_4495.JPG Does anybody have a good source for the 3.9 ohm 20watt power resistor? I have tried digi, mouser,Newark, google and some smaller shops. The closest is 4 ohm 20watts @ 5% which is within tolerance of 3.9 @ 10%. Unfortunately it's from china and is going to be 3-4 weeks.
    Any suggestions?
     
  8. Hyperion

    Hyperion Roobarb & Custard Subscriber

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  9. Bigdrive

    Bigdrive Member

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    Do you think the lower wattage will matter if I just use it for testing and easy listening???
     
  10. Willy6

    Willy6 AK Subscriber Subscriber

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    I put a 25W 3.9ohm 5% resistor in mine and it works fine..Available at mouser or digikey..
     
  11. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    IMG_4497.JPG Waiting for shipment from mouser, I decided to catch up with trimmer pots on mc 2917/2918. Note these boards will not be installed in unit until I get a MC cartridge, which could be years.

    I remove old ones and take measurements to rough in a adjustment on the new pot. All pots have been as per SM, but these two. They read 205 and 185 ohms across the outer pins and are marked 220 as per picture. They are suppose to be 100 ohm by SM. I know many have said replace what you take off, not what's in the SM.

    I think Harolda found one wrong one one his amp that he thought had been installed wrong from Sansui. These two also look original solder joints.

    So what does everybody else have in those positions?
     

     

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  12. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Well, you have two boards to look at, and it would be very unlikely that Sansui would made a mistake with both, and your amplifier has worked with the values in it now - I say put in 200 ohm replacements as per original - I can't remember what I put in mine.
     
  13. Bigdrive

    Bigdrive Member

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    98
    Location:
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    True.

    I have learned from you that you don't change from what's there!

    The voltages were set both before I started and after I recapped but I never heard the board as I don't have a MC cartridge.
    I don't think Sansui made a mistake in installing them, just that in the SM there is a difference between it and my model.

    Someone else should have come across this other than just me.

    Seems there should be a resistor change also. I will check skematic for other differences.

    Also can anyone recommend binding post. I have some from digikey but don't like them. Yes I like the gold ones that can short out! I don't have access to equipment other than a drill:)
     
  14. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I agree the binding posts don't age well, I'd like to think they felt more robust when they were new :)

    This is a great amplifier, don't cheap out on binding posts - spend a little more to make it much less likely that a short could take out as many as six :yikes: :bye: of those precious OP transistors - don't you think?
     
  15. ghamilton

    ghamilton Super Member

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    This is what I did for the binding post.....http://audiokarma.org/forums/index.php?threads/919-binding-posts-replacement.243497/
     
  16. Bigdrive

    Bigdrive Member

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    98
    Location:
    Kelowna
    Updates...been away due to family matters....

    I got the 4ohm 20 watt as a temp and installed it. I checked all voltages and found the bias was out of limits on one driver board. I removed the amp and put back in the original trimmer and replaced all resistors in the trimmer circuit. Put it all together and bias was adjusted to spec. Waiting for driver to come out again to put trimmer back in. While it was out I replaced r36 and r37 even though they were within spec but everybody changes.

    Back to happy days listening to and enjoying the amp.....

    Decided one night to check temps. Remember, my outputs were running .003 and I just had to plane them. A lot of good advise to just add more grease but it was not in me. They were all planned to .002 to .0015. Well, I never measured the heat from the unit to begin with, but it is cool as a cucumber now. Start temp 69F, 4 hours of listening at -24 volume and drivers at full it hit 85F. If anybody else has temp measurements let me know.

    I have purchased a scope, signal gen, and load band to start to see if it is stabile.

    The next tear down includes the above and to replace the rca to gold plated.

    And now for the questions.....

    I am doing a AU-717 for my sister and it is capable of preamp out and amp in at the same time. I have reviewed the SM for the AUX1 and to me it seems like it should also do this but mine does not, is this normal for the unit? The brochure suggests it is suppose to, to enable a peroblic equalizer.

    Looking for help, thanks.
     

     

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  17. Bigdrive

    Bigdrive Member

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    I had a chance to check output volts the other day and was very surprised at the results. It was only putting out 120 watts into dummy loads before clipping on sine wave 1KHZ!
    I had finally received a 4.0 25 watt protection resistor and thought that might be causing the problem. So it was changed out.

    New test with new part, 152 watts from both channels. Still a little disappointing. The outputs have been checked for HFE at least 3 times and were within limits.

    Dumb question, where to the volts at the output come from?
     
  18. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    The power supply.
     
  19. Bigdrive

    Bigdrive Member

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    Is that where I should look for the shortfall in output watts?

    The power supply has been done except for the 4700@25v. I have them now but I am not sure if I want to put the in Panasonic HE I have or order the Panasonic 4700@35 FC
     
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Those capacitors are the primary filtering for the +/-11V supplies for the MC Head Amps, so unless you are using the MC inputs for your power output measurements they have nothing to do with the results you are getting. I recommend using the Panasonic HE.

    So the AU-X1 is rated at 160Wpc and you are worrying about an 8Wpc shortfall in a 40 year old amplifier, that if you'll forgive me saying, has not received a full professional restore. How sure are you that the output voltage from your signal generator, or the line voltage you are running the whole amplifier from is not a few percent low? - and the accuracy of your true RMS voltmeter measuring the output voltage? the accuracy or your 8 ohm loads? - really 8W ! - don't worry about it. :)
     
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