Can I fix a Sansui au X701?

Discussion in 'Exclusively Sansui' started by Infernosaint, Jan 20, 2012.

  1. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    As far as my brief search reveals these 'paired' resistors are no longer available - so you might have to buy 2 and possibly drill a hole in the PCB to accept the other resistor wire.

    Well, we could try and teach you - but this would be a steep learning curve.

    Yes, without verifying the state of the outputs and the driver transistors - not a good idea. And even when you have done this I feel sure you will need a DBT to assist with further diagnosis/troubleshooting.

    Knowing what we know now, that the emitter resistor(s) died, I think it very likely the output transistors (qty 2) are toast.
     
  2. Infernosaint

    Infernosaint New Member

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    35
    So I need to replace r67, and r69 with two .22Ω resistors paired.
    Any other obvious components, other than the transistors, that could have died from this. So I can check them.

    I'm guessing my meter needs a diode check function for the transistor check?
     
  3. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    You'll need to check

    kQ54, kQ56, kQ58, kQ60 = drivers

    & kQ62, kQ64 = outputs

    The ones in bold are the ones most likely to have taken a 'hit'

    And all the resistors around them that's 6 - not including the 2 emitter resistors.

    Let us know how you get on.
     
  4. Infernosaint

    Infernosaint New Member

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    I can check the 6 resistors now.

    I have located all the resistors- I mean transistors.
    But I'm still not sure how to go about it, or if my meter has the means.
     
    Last edited: Oct 18, 2012
  5. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Does your meter have an Ω range ? - do you know how to use it ?

    Do you have the schematic? - you can't do without this now.

    I suggest you de-solder 1 leg of each resistor to be tested - this will allow you to get a true reading from each. Just select the Ω range on your meter and connect the probes 1 to each end of the resistor ??? I suggest you write down the readings you get and note the resistor circuit reference (R67 etc...) as you go.

    And report back
     
  6. Infernosaint

    Infernosaint New Member

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    Never mind.
     
    Last edited: Oct 18, 2012
  7. Infernosaint

    Infernosaint New Member

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    Oh, wow, my bad. I know how to measure resistors, I meant the transistors there, didn't realise till now.

    I don't know how to do transistors, was what I meant. Sorry >.<
     
  8. bluesky

    bluesky Addicted Member

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    Sure you can fix it.

    I've seen X701 sell for $94 (should of bought it but I wasn't watching the end of the auction) to $275. Sonically, it's a great amp. It's a international Sansui alpha. Great amp!

    If the X701 is an easy fix...do it. You will be in sonic Sansui heaven.

    It all comes down to if it's 'cost effective', as it is with any piece of equipment. And the ' love ' for the amp. And what you know it can do.

    The X701 (which I've never heard) and the X901 (which I own and use) are really nice!!!!!!!!! Audiophile type.

    Hope this helps.
     
    Last edited: Oct 18, 2012
  9. Hyperion

    Hyperion Roobarb & Custard Subscriber

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  10. Infernosaint

    Infernosaint New Member

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    Thanks, I'll take some time to learn this stuff, then test everything, and replace what i can.

    Do you think this happened because I turned the trimpot all the way to either side? Is this even probable?
     
  11. eradoncic

    eradoncic Active Member

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    :scratch2:
    theoretically, it is possible, but the bias trimmer has two serial resistors which serves as some kind of protection to prevent the excessive biasing of the OT in case the trimmer is lost the viper contact (e.g.because of dirt etc).

    But, if the cooling paste on the heatsink is old and dry, then dissipation of the heat to the heatsink is bad, and it is possible to thermal breakdown of the OTs
    Personally I doubt this, since I know very well this model, and it is very well protected. It is more probable scenario of some bad joint of any resistor, or something trivial as that.

    I remember, for example, two personnel situations, one described here: http://www.audiokarma.org/forums/showthread.php?t=19449

    - during biasing the OT, suddenly one pair cracked without any visible reason; it was real detective work to find the replacement

    - the second one was on my X701: I replaced everything you did and explained here, and blowed the trannies (one pair) immedately after turning it on:thumbsdn::sigh:

    I was mad until I find the culprit - a piece of wire, resting after the cutting the excessive lead after soldering few resistors :tears:. I did not noticed that 1/2" piece which was exactly among the legs of one of the output transistors, bypassing/shorting something (base, collector/emitter).

    My point is, a really trivial thing can be a cause
     
  12. Infernosaint

    Infernosaint New Member

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    Well, after replacing everything, I turned it on, just to see if it would come out of protection. Gave it a good 30 seconds, then turned it off and got the multimeter out.

    I think it was on for maybe 2½ minute max, while I got the probes to the resistor and was adjusting the trimmer. After having it all the way CCW, I guessed something might not be right, and maybe gave it one turn CW before the paired resistor and r67 went up with a flash and a crack.

    Again, I just assumed that it might be something to do with my adjusting since it was only that "channel" out of four that blew up. The one I was fiddling with. None of the other paired resistors were even warm.
     
  13. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    This is about the best I can find for replacement emitter resistors, which for those who can find a better choice maybe? are 0.22Ω, 5W resistors. The originals are 0.22Ω +0.22Ω in one 3 pin package 10mm lead spacing.

    So you will need 2 of these, unless someone comes up with a better source/choice.

    http://uk.mouser.com/ProductDetail/...=sGAEpiMZZMvNd0dY0Kymzgm5KkyiXWqGVQoN/GGtHrk=

    The ordinary resistors should not be a problem.

    And B&D has all the transistors - 2 outputs 2SC3284/2SA1303 & 2 drivers 2SA1606/2SC4159

    Also this might help
    http://www.talkingelectronics.com/pay/BEC-3/Page66.html
     
    Last edited: Oct 20, 2012
  14. Infernosaint

    Infernosaint New Member

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    I've tested the 4 easy to get to transistors, meaning all but the 2 attached to the heatsink. I'm gonna have to take some time to disassemble that, to get them out and test them. One of the four transistors were dead. The others were functioning as they should, measuring 1.1-1.3 on the 2kΩ/diode test.
     
  15. Infernosaint

    Infernosaint New Member

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    35
    Okay, I've finally gotten around to testing the driver and output transistors, half of them dead. I have now ordered replacements for those, as well as the paired resistor (dual emitter).

    So:

    1. I replace everything that died.

    2. Do I re-center the bourns? By turning it all the way and then half back (12.5 turns)

    3. Do I just try again, doing bias for the same channel that blew up (this time with working meter, and seeing if the resistor gets hot (none of the other did))


    Is there a problem with less-than-decent solderings, as long as they're not shorting anything? I had a few traces lift, and did my best to fix it, if needed with a lead going to the nearest solderpad on the same trace. I know this is not optimal, but if it's not critical (again, as long as nothing is shorted, or smeared all over the place) I could live with that, as this amp is probably not gonna stick around forever, with all my blowing up stuff and amateur soldering. For now, getting it to work would be an immense improvement over the cheap surround amp I'm borrowing at the moment.
     
  16. BigElCat

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  17. Infernosaint

    Infernosaint New Member

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    Well the ones where I had to redirect the lead from the caps to the nearest solder pad, because the one it was supposed to solder to, lifted and messed up. I'd say those are worse.
    But again, if this does not mess anything up, like lots of noise or something. As long as the connection is fine, and not shorted, I'd be fine?
     
  18. BigElCat

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    As long as you are on the F5693 amp board, I think you'll be okay. I can't hear my trace lifts on this board. It's said to be a 'non-signal path' circuit. Best to you! The printed circuit boards are actually numbered (with silk screen labels).
     
  19. BigElCat

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  20. marantzfan

    marantzfan ... Subscriber

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    After years of service, my X701 just went into protection. Time to finally open it up, get things sorted out and do a recap while I'm in there.

    Bookmarked!
     

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