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Odd issue with Sansui 1000A

Discussion in 'Tube Audio' started by nabeelsayegh, Dec 28, 2017.

  1. nabeelsayegh

    nabeelsayegh Active Member

    Messages:
    218
    Location:
    Joliet, IL
    running into a weird issue where i only get output to the left channel when selecting AM (sharp/broad) or FM. both channels work fine in FM stereo MPX or any other input (aux, phono, tape). Before i tear this one apart....anyone ever run into this? I am thinking to remove and clean the input selection pot but i have a feeling it may not be the issue.
     

     

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  2. Big Harry

    Big Harry Active Member

    Messages:
    232
    Location:
    Hawthorne, California
    You could have a dirty switch. Try cleaning them before doing anything else. I had to replace the volume and balance pots in my 1000A a few years ago because of channel drop out, but I don't believe that is your problem.
     
  3. nabeelsayegh

    nabeelsayegh Active Member

    Messages:
    218
    Location:
    Joliet, IL
    pulled the switch/pot and cleaned it very well. Did a continuity tests on the contacts and it is not the problem. swept through and checked all diodes....they are working fine. caps and resistors around the tuner front end all check out.
     
  4. nabeelsayegh

    nabeelsayegh Active Member

    Messages:
    218
    Location:
    Joliet, IL
    Alright...this is messed up. This particular 1000A was not wired to output AM/FM to both the left and right channels....only the left. MPX FM stereo was only multi-channel. Now, i can only assume one of two things three things is going on here. 1....this was the manufactures original intent. 2....they messed up and did not wire it correctly (not likely). 3....at some point in this units life, the selector switch was replaced and not wired up correctly. I really don't think number 3 is likely either as the selector switch does not show any signs of being removed. Solder pads look original. it get's even more strange. I got a friend with one of these and apparently, his unit puts out AM/FM to both L/R channels no problem. I had him send me pics of the top and bottom of the selector switch and sure enough, there are jumpers between wiring pads on sections B and C for the AM and FM feeds. This confirms it is wiring, but what i am not sure is if someone modded his or if i got a lemon. In any case, problem solved.
     
  5. s-petersen

    s-petersen Scott

    Messages:
    4,523
    Location:
    Middletown,New York
    I wouldn't rule that out, a Pioneer I recently worked on had an electrolytic cap backwards from the factory.
     
  6. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,579
    Location:
    Southern NJ
    Several caps in my '53 Philco TV were installed without a drop of solder ever having touched them. It happens.
     

     

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  7. nabeelsayegh

    nabeelsayegh Active Member

    Messages:
    218
    Location:
    Joliet, IL
    The sad part is how many hours i spent trying to troubleshoot this only to find out it was not even connected. But you guys are right it is possible this one got 'missed'.
    :dunno:
     
  8. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    It was a Monday Morning Build. The Line Gnome who was doing that particular section, had too much SAKE and squid over the weekend. Possibly some bad sushi too.

    Does anyone else's pop thru the speaker when switching to The Tuner? I was told sometime back that this was normal and the switching also engaged some voltage or other. It's not a deal breaker when using but I'm kind of getting tired of turning off the speakers before switching to tuner and then turning on the speakers again.
     
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  9. Big Harry

    Big Harry Active Member

    Messages:
    232
    Location:
    Hawthorne, California
    I just checked my 1000a and it doesn't pop when operating the selector switch. It does however make a slight click when using the input selector.
     
  10. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,579
    Location:
    Southern NJ
    if it switches B+ off when you turn it from tuner, you'll get an arc as it re-connects. Try bridging a resistor across it to tickle some B+ into the tuner. Helps keep the tubes alive, and it may reduce the pop noise. I did that with my Pilot tuner/pre and its better behaved now. Also I should hopefully never again have to replace the AM section tubes from sitting for years with no plate voltage.
     
  11. s-petersen

    s-petersen Scott

    Messages:
    4,523
    Location:
    Middletown,New York
    Sometimes it is a bad coupling cap bleeding DC into the switch
     

     

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  12. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    It's done it since day 1. It's been rebuilt, every cap (except the tuner ceramics)has been replaced with good films(ecq, dme, mkp's,715p's) and lytics (Nichicon upw/ukl), all of the signal tubes replaced along with about 2/3 of the tuner and MPX tubes. Don't get me wrong, it runs fantastically good, and is now not any hotter than my 800c due to some mods to the power resistors, and HVAC aluminium tape on the transformer sides that face the tubes. OPT Tubes are Tungsol 7591 ReIssues with the smaller original sized bottle. I listen to a lot of radio, so it's not really a problem for me here, but if I listen to a tape, then go back to FM it has a nasty POP! I've gotten to the point of turning the spkrs off, switching to FM, then turning the spkrs on. Around the switches its a briar patch! Brer Rabbit would love it, but I ain't jumpin into no briar patch!!!
     
  13. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,579
    Location:
    Southern NJ
    Pretty sure I did the actual bridge on my Pilot away from the switch, too much of a CF. Electrically it jumps the contacts on the switch, physically the resistor is somewhere that was easy to access. I've messed with selectors before, its usually a horror show and I avoid it whenever possible.

    no guarantee it'll change anything but you should be able to use some clip leads to patch it in there for testing. If it doesn't do anything, pull the clip leads and put the lid back on.
     
    Last edited: Dec 30, 2017
  14. primosounds

    primosounds SE KT120 w/ 6J5G drivers. Subscriber

    Messages:
    2,641
    Location:
    Terra, 21st century CE
    Squid!!!! For your edification that is Tako . No racial bias intended ........gaijin:idea:.
     
  15. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    KEE-RIST! :eek:The P.C. Police are everywhere. Worse than the Trolls:naughty: in the CIA. :D
    And now I'm supposed to be multi-lingual????? I speak AMERICAN ENGLISH. I've got a polyglot of Northern and Southern Calif. Mid-Atlantic, New England, and Hawaiian in my accent. And That's enough!
     
    Last edited: Dec 31, 2017
  16. sanford12

    sanford12 Old Stuff New Stuff As long as it's Good Stuff Subscriber

    Messages:
    3,521
    Location:
    Blue grass country
    Mine would always pop with the selector switch. Looks like you have an easy fix and that's a good thing.
     

     

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  17. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    Thain; What size resistor. The voltage that is switched is 100+ VDC.
     
  18. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,579
    Location:
    Southern NJ
    Couldn't tell you what I used, likely whatever was close at hand. May have been 100K, I'm sure I started with some random resistor that was in reach and went up or down depending on how it worked out. I left whatever gave me 10-15 volts on the plates.
     
  19. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,791
    Location:
    Glen Burnie Md.
    OK. Good enough. Thanks.
     

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