BA-5000 with Issues

Discussion in 'Exclusively Sansui' started by Fhamre, May 3, 2018.

  1. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,275
    Location:
    uk.. the middle bit
    i asked how long it was stored ..no mention on the box.. it works though ..best cough medicine for a good while ..
     
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  2. Fhamre

    Fhamre AK Subscriber Subscriber

    Nice so we both have a buzz!
     
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  3. Fhamre

    Fhamre AK Subscriber Subscriber

    S701 is a slide switch for Stereo/ mono mode.No mute switch on the 5000.
     
  4. Fhamre

    Fhamre AK Subscriber Subscriber

    To be a little more precise the low buzz occurs as soon as the protection light goes out and lasts about 1 second.
    This is probably normal but I put my meter to measure DC on the speaker terminals and on power up you get a quick surge to about 3 volts before it quickly settles down to about 10-15mv per channel.
     
  5. richardpp

    richardpp Active Member

    Messages:
    108
    Location:
    Adl, Australia
    Not sure if it's relevant but I had a buzzing from the protection relay in an AU-20000 as it tried to pull down, using a 100W bulb BDT at the time. I felt like the DBT was just holding the relay back. Occasional contact and protection light would flicker and eventually go out. This was an audible buzz from the relay itself, no speakers connected.

    Edit: Wasn't sure from earlier posts if you had changed the value of the ballast resistors and if this could have made a difference
     
    Last edited: May 11, 2018
  6. Fhamre

    Fhamre AK Subscriber Subscriber

    No I did not change the value of the soft start resistors.
    Now going back to the beginning. This unit was working when I bought it.
    I put it on my bench without a DBT and cooked the soft start resistors.
    I have since recapped the entire unit with the exception of the ps caps,replacing the 1212's and the 818's and 1628's. Installed new soft start resistors.
    So now the unit seems to be working. Bias is bang on and DC offset is good. Still have an annoying little buzz when relay engages.
    But apparently that is not all the issues. I thought I would try the old relay so I put it back in. So I put the unit on its side change the relay and to be safe used my dbt to power up. Well don't I get the bright lights.
    Put the new relay back in. Same glow. Then I put the unit back on its bottom and test,all good. Put the old relay in no glow but same buzz. Put the unit on its side in effort to try and find what is going on and I get the glow on power up.
    Check connections including the power cord as I know there were changes there.
    Bottom line every once in awhile especially after moving the unit I may get the glow/short on power up.
    Can't pin point the issue at this point.
    I am running out of hair to pull!
     

     

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  7. Fhamre

    Fhamre AK Subscriber Subscriber

    I think the issue may be related to the power plug that was added. Can't be sure but I tried another power chord and got the glow. Wiggled it a bit and no glow on start up.
    Will continue to investigate.
     
  8. kevzep

    kevzep Its all about the Music Subscriber

    I had an interesting one with my old G22000 I was servicing and repairing.
    I was adjusting the bias, and in doing so, leaned on the chassis with my wrist, and got a full mains shock albeit a low current one.
    I measured between chassis and ground and sure enough, full mains voltage on the chassis.

    There was no logic behind this as I could not see anything....

    However, what it ended up being, was the old power cable, the insulation had gone kind of soft, and at the place where it goes through the gland and into the chassis, the clamping effect had exposed some of the copper...
    So it was a partial short. I had to use a new cable, and this time I used 3 core and hooked the earth up.

    So, you might be having something similar going on?
     
  9. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,275
    Location:
    uk.. the middle bit
    yes insulation can and does go leaky ..
    i would however expect the buzz to remain and not be short term .. ac current on a dc relay might well do this . like if a supply filter cap isnt up to it or a flaky rectifier diode .
    i do think its something loose or cracked and moving whilst the unit is being moved to work on .
    p.s try working on a samick smp-4000 .. simply unplugging audio input to a main board makes you think something is seriously wrong .. the grounding system is rather odd .
     
  10. Fhamre

    Fhamre AK Subscriber Subscriber

    Well I do notice the fellow didn't ground the three prong to the chassis. Changing the power cord still ran into the same problem but it also went away.So I don't believe its the cord itself.
    IMG_1683.JPG
    The fellow used solid copper wire and wrapped foil over it and then tape.
     
  11. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,275
    Location:
    uk.. the middle bit
    green tape too .. hope you have the missing screws ...
     

     

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  12. kevzep

    kevzep Its all about the Music Subscriber

    Oh good god, what a hack job!!
     
  13. Fhamre

    Fhamre AK Subscriber Subscriber

    Yes the screws were just removed.
     
  14. Fhamre

    Fhamre AK Subscriber Subscriber

    Well I pulled that plug rewired and soldered it and put it back in. Also grounded it to the chassis.
    I did a couple of tests and it passed but will need to do more unit movement to be sure and well I 'm tired of flipping the beast,today.
    Still got the buzz.
    Wondering if its worth the effort to replace the two regulators on the PS CB( low voltage) F-2521. There are a few small signal transistors on that board as well I could sub out while I'm at it.
    Any thoughts?
    IMG_1686.JPG
     
  15. Overundr1

    Overundr1 AK Subscriber Subscriber

    Messages:
    2,501
    Location:
    Mississippi
    This may seem a bit strange, have you tested for hum with the bottom cover on the unit. Seems to me several Sansui amps I have worked on would talk a little bit till the covers were all in place.
     
  16. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Was it wired to the chassis before ?


    Nevermind-------------------------------
    Personally I wouldn't ground it.
     

     

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  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Pioneers as well.
     
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,070
    Location:
    Fort Dodge, Iowa
    Well one issue with polarized IEC cord. There is a right way and a wrong way to wire it. The wrong way causes hum and a slight tingle is felt on the metal chassis.
     
  19. Fhamre

    Fhamre AK Subscriber Subscriber

    Well knowing my track record I wired it wrong.If it causes issues I will clip the ground.
    Eventually I will get the cover on and test for him.
    Still looking for ideas on what be the cause off the short buzz/small fart sound when relay engages.
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,070
    Location:
    Fort Dodge, Iowa
    Nuetral is connected to earth ground at the breaker box. Miswired puts hot on the ground within your amplifier. Hummmmmmmmmmm & tingle. AC hot is very noisy.
    upload_2018-5-11_20-51-3.png
     
    Last edited: May 11, 2018

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