My Sansui 400 just stopped working

Discussion in 'Exclusively Sansui' started by matmat, Apr 6, 2017.

  1. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Hi all,

    I've had this receiver for about 4 years, and it's been working like a charm (after the initial clean-up when I first bought it).
    Then today, I heard a faint pop, and it stopped working normally. To be more precise, it does power on (the display lights up), but there is no more sound on the right channel, and the left channel seems to be very low and distorted when playing Phono. When playing Aux, the right channel is silent as well, but the left channel seems to sound normal. The FM source doesn't seem to be working at all on either channel.
    Switching from speakers to headphones doesn't make a difference.

    Any ideas what the problem might be, and how to solve it?

    Thanks a lot!
     
  2. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    I just realized I had a typo in the title: it's a Sansui 4000, not 400. Sorry about that.
     
  3. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    I looked behind the receiver, and I think some speaker wires might have been touching (probably while I was moving furniture around to clean yesterday).
    I checked the fuses, but they look normal. And when I switch them around (left to right and vice-versa), the dead channel remains on the same side.

    Could it be a transistor? How can I find out? I could open it up, but I don't know what to look for. Any help appreciated!
     
  4. slimecity

    slimecity Super Member

    Messages:
    1,590
    Location:
    New Zealand
    If you think speaker wires may have been touching then we will need to presume that the problem may be a blown output or two. Im not familiar with this unit but open it up and look for any internal fuses. If there aren't any - and you feel that you can do this - get a DMM meter and pull the output transistors for that channel - they are the large silver transistors in the black heatsink at the back of the unit. There are instructions here on this site for a 6-way transistor test using the diode setting on your meter.

    Go here first, register and download the service manual: https://www.hifiengine.com/manual_library/sansui/4000.shtml
     
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  5. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thanks a lot for your help.

    I need to get my hands on a better multimeter than the cheap analog one that I own, and I will check the transistors and report back. Thanks again!
     
  6. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

    Messages:
    19,803
    Location:
    Glen Burnie Md.
    There are two "protection" fuses(3.5A) on the back. Check them with a DMM (visual doesn't cut it in most cases, especially when the fusing element separates at the end under the end cap), if ok clean the ends and make sure they are tight in the retainers. A bad one will cause similar symptoms to what you are experiencing. Then go up in complexity with checking the transistors, etc.

    Once you get it running and haven't done this yet, check the voltage selector. Chances are it's set to 117v. Change it so the selector is set to 127v. This will change the winding capacity so it can handle the increase in today's wall voltage. It won't hurt the unit. But it will help cool down the transformer some.
     
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  7. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thank you. I tested the fuses and they're fine.

    But then I tested the transistors, and all four give me zero readings. Does that mean they're all dead ansld need to be replaced?

    They are 2sd213. Is there anything I should know about replacement? I see a set of four 2sc1116A (supposedly what the Sansui 4000 calls for) on eBay, should I get those, or look somewhere else?
     
  8. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    While searching on this forum, I read that it's best to avoid eBay for transistors. I also read that MJ15022G/MJ15023G are a good replacement for 2SC1116A. Can someone confirm?

    If the 2SD213 were all NPN, should I replace with four NPN as well (MJ15022G)?
    Or should I have two NPN (MJ15022G) and two PNP (MJ15023G) as I've read it in some places?
     
  9. slimecity

    slimecity Super Member

    Messages:
    1,590
    Location:
    New Zealand
    What you have is an amplifier with non-complementary output - meaning that the outputs are one type of transistor, rather than even sets of NPN/PNP. In your case its NPN.

    No, do not buy any of the shite touted as "new" from China on ebay, very risky and likely to be fake. Unless you can find a genuine supplier of good parts. Some of the 4000s also had 2SC1116 instead of 2SD213 - finding some of these genuine Sanken units would be great (however possibly unlikely).

    A replacement for the 2SD213 is the 2N3055 and a replacement for the 2SC1116 is a MJ15011. The 2N3055 is very common however you can do better. Unless there are any objections (possibly due to the speed of the originals vs the replacements) - not sure why you cant just "uprate" the specs and go with 4 x MJ21194 NPNs to replace all of your 2SD213s.
     
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  10. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thanks a million, this is very helpful.

    I'll go ahead and order four MJ21194 from Newark or Mouser, then.
    When installing them, do I need to bother with reapplying thermal paste, or can I just put them on, with the old washers?
     
  11. slimecity

    slimecity Super Member

    Messages:
    1,590
    Location:
    New Zealand
    I'd suggest don't order them yet - I'd like to see if others more knowledgable agree with me or not. cheers
     
  12. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    OK no problem, I will wait for someone else to confirm. Thanks for the advice!
     
  13. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Can anyone else confirm that it's safe to go with MJ21194 for my Sansui 4000?

    Thank you!
     
  14. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Last try... Anyone?
     
  15. skippy124

    skippy124 AK Subscriber Subscriber

    Messages:
    1,554
    Location:
    Sydney Australia
    Hi,

    I recently repaired a 4000, outputs blown on one channel, also took out one of the driver transistors (caused by the triple diode going O/C. Used MJ21194's for the ouputs without any issues.

    Strongly suggest that you research and build a dim bulb tester if replacing blown outputs and you are unsure of the serviceability of the driver circuits.

    Cheers
    John
     
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  16. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thank you for the precious information, John. I am new at this, perhaps you could explain the risk of replacing the outputs without a dim bulb tester? What is the likelihood of driver circuits being damaged?
     
  17. Mr. Nick

    Mr. Nick New Member

    Messages:
    30
    The risk is that also driver transistors were damaged on the driver stage. If you just replace the outputs and turn the unit on, those new outputs may blow up again and cause even further damage to the circuit components.
    And likelihood is just you don't know, until you pull them out for testing.
     
  18. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thanks a lot. I will make sure to test the driver circuits then.

    Unfortunately I have no idea what to look for. Which board(s) do I need to test, and how?

    I was just given a little DC bulb tester with a 9V battery, would that do the trick?
     
  19. Hipocrates

    Hipocrates Anti-Muppet Subscriber

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    Location:
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  20. matmat

    matmat New Member

    Messages:
    48
    Location:
    Brooklyn, NY
    Thanks a lot, Hipocrates.

    I'm in the process of building my DBT, with a 100W bulb. Once I'm done, is there a safe way to test it before plugging in? I'm being as careful as possible, but I've never done this before and don't want to blow anything up.

    Also, trying to make sure I understand the process. Do I need to replace all the output transistors (I have ordered the replacements), then plug the receiver through the DBT, and turn it on?
    Or should the DBT test happen before I change the transistors?

    Thanks again, and sorry for my ignorance. Trying to learn!
     

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