problem with my 999

Discussion in 'Exclusively Sansui' started by stevestadler, Jul 24, 2016.

  1. stevestadler

    stevestadler Member

    Messages:
    51
    I'm trying to make a 999 from 2 defective one, I have a problem that I cannot found, every time I insert the
    1159 I blow the positive fused on the right channel, the 1277 board side
    can someone be nice enough to give me the voltage from pin 1 to 14 I just want to verify if I have the right voltage

    Thanks
     
  2. slimecity

    slimecity Super Member

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    I cant remember but is that fuse the fuse for the biasing circuit? If so, reduce the bias-adjusting pot to zero and try again.

    Otherwise, have you tested the output transistors and pre-drivers on that side?
     
  3. stevestadler

    stevestadler Member

    Messages:
    51
    Thanks for the reply

    its the fuse just beside the f-1159 the one that carry positive current, I replace all transistor on the au999 I also replace almost everything on the 1159 boards.
    Between the pin 5 and 7 of the 1559 I can see smoke from the resistor
     
  4. slimecity

    slimecity Super Member

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    For starters make a dim bulb bulb tester and only power up the amp using that - threads on here on how to make one.

    Did you also replace the main output transistors?
     
  5. stevestadler

    stevestadler Member

    Messages:
    51
    thanks for the tip, I already replace a lots of fuse
    yes I replace the 2sc680 2sa566 and the 4 output 2sc898
     
  6. petehall347

    petehall347 the brandy coffee man

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    voltages are on the schematic from hi-fi engine .
    to start you off b1 and b2 are 44v . the smoking resistor is a shorted driver or it is being over voltaged . or some other problem .
    i would get the power supply checked over first .then get one channel working so you have reference.
    p.s what transistors did you use as replacements ? i think originals will be obsolete by now .
     
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  7. w1jim

    w1jim I can fix it but good... Subscriber

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    Double check that the output transistors all have the insulating mica pieces installed.
    Been there!
     
  8. stereofun

    stereofun Super Member

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    You can also swap 1159's. If the right fuse keeps blowing it's not the board. If it's stops blowing it's the board related and you can focus there. Thoroughly check pin outs, compare traces with " good board" - good luck.
     
  9. kevzep

    kevzep Its all about the Music Subscriber

    Blowing the rail fuse eh? Which one, positive or negative?
    DO NOT put any more fuses in until the issue has been identified.

    These are the simplest and easiest amps to work on, very straight forward.

    Test all output transistors
    Test Driver transistors
    Move onto the driver board and test all semiconductors. (transistors and diodes)
    Test all resistors on the driver board.
    Be VERY careful not to break a leg off the bias transistor when removing the driver board.

    Take as many pictures to show the detail of the work you have done. Nice clear pictures.

    List the substitutes you have used for the work you have done so we can check your work...

    We'll be waiting for the details, you will get this amp going, they are nice and easy to work on...
     
  10. stevestadler

    stevestadler Member

    Messages:
    51
    ok thanks, I turning around in circle for a while
    I use what people said for equivalent
    replace 2sc898 with mj21194g
    2sa566 with 2n3741
    2sc680 with 2n5050
    I try the dim bulb tester no light and ampli turn on,
    when I insert the 1159 the bulb light out very bright and the amp doesnt power up i try the other 1159, same thing
     
  11. stereofun

    stereofun Super Member

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    1,119
    Location:
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    Quick test to do - use the continuity check function on your meter to to check for continuity between the outputs and drivers casing (collector) and the heat sink/ plate to which they are mounted. You want zero continuity. Can you give the part number of the particular resistor that fries (Rxxx) - this may help us trace the problem back. If you have done soldering on the blue slots that holds the drivers you should carefully check your joints - here you can compare the layout to the "good" left side (keep in mind they are 180 degrees from one another). Since both driver boards are causing the short, we can almost assume those are not the problem, unless you did some wrong transistor pin-out on both ? Have you replaced the rectifier ? Again carefully check your work everywhere you have been and as kevzep says, add some photos of your work sofar.

    On a separate note, I'd stay clear of those drivers. The originals are rated at 50 mhz speed. Your replacements are exceedingly slow at 3-4 mhz range. The MJ15033/32 are min. 30 mhz and a much better alternative, even with different cases they are quite easy to mount. I also like the MJ's since they are made by same manufacturer, likely sharing some characteristics and a tested and tried combo as driver / output pair. But first - find out whats going on!
     
  12. kevzep

    kevzep Its all about the Music Subscriber

    Wont be the rectifier at fault, that would blow the mains fuse, but once we see a pic, we can see if it is original, if so would be a good idea to replace.

    Use MJE15028G, MJE15029G (120V as opposed to 250v which is not necessary) for the drivers, they are TO220's but can easily be fitted to the TO66 sockets.

    Could be something on the driver board if they have both been worked on and the same parts have been replaced incorrectly, which is why we need to see detailed pictures.

    We'll wait for more information and pics.....

    I am about to do work on two AU999's so I am in the mode so to speak!!
     
  13. slimecity

    slimecity Super Member

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    I second this. Listen to these guys - Kevzep is the man for the 999. You will be getting some great help here.
     
  14. petehall347

    petehall347 the brandy coffee man

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    Location:
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    did you try removing the outputs to see if it then powers up on dim bulb ?
    p.s do not have anything into speaker outs until it is fixed .
     
  15. stereofun

    stereofun Super Member

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    Yes, listen to Kevzep all you can :thumbsup: - once this fault is corrected, please do change the drivers, preferably onsemi MJE15028/29 or 15030/31 - For future reference, Here is how you can fit, including a more professional alternative by AK member Kale. OK - bring on the pics and the R number of the resistor that smokes - we like to solve mysteries.
     
  16. petehall347

    petehall347 the brandy coffee man

    Messages:
    23,883
    Location:
    uk.. the middle bit
    the resistor is looking like r847 15 ohm best i can make out .op says it is between pins 7 and 5
    i find it odd that one is smoking first i would expect a higher ohms to smoke first . i think there must be a hard short . although looking again the other driver emitter resistor is 1/2 watt .
    might be tr813 is bad .
    all transistors need checking really .
    outputs pulled first to see what happens like i said before .
    on another note is it possible to put the board in the wrong way round ? not saying try it it was just a thought .
     
  17. kevzep

    kevzep Its all about the Music Subscriber

    He needs to post pics so we can see the work done and transistor orientation....
    There will be a short or a wrong polarity transistor somewhere, but lets not speculate until we have information first, otherwise he'll be chasing stuff without really knowing whats going on....
     
  18. petehall347

    petehall347 the brandy coffee man

    Messages:
    23,883
    Location:
    uk.. the middle bit
    yes exactly correct . am looking forwards to seeing some pics myself .
     
  19. stevestadler

    stevestadler Member

    Messages:
    51
    I replace every caps on the amps and every transistor, I replace the rectifier with the b250c and the transistor on the 1277 by the 2sc2904
    P.S I run out of 1/2 watts resistor , so I used 2 resistor at double the value
     

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  20. stevestadler

    stevestadler Member

    Messages:
    51
    some more picture
     

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