Balance control problem on Panasonic SG-999

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  • jimkarl
    Member
    • Jul 2014
    • 37
    • USA

    #1

    Balance control problem on Panasonic SG-999

    Have a vintage Panasonic SG-999 integrated stereo, pop up turntable experiencing a strange balance control problem. On one channel, the balance control works fine, meaning if you start center and go to one end it attenuates and fades the signal on that channel down to zero. On the other channel, the control has no effect. It is always on, regardless of the balance control setting. I disassembled and removed the balance pot (R4 on the schematic, 100K with three terminals). Was certain that had to be the problem but using a resistance meter, center pin to end pin(s), it seems to work fine. Reads about 61K to zero as you sweep the control, on both pin combinations. So if the pot is good, there must be something in the circuit bypassing the signal through, ala short someplace, but only in the one direction. Where in the signal path should I be looking? Link to a portion of the schematic is here:

    http://home.comcast.net/~jimkarl/Pan...schematic1.jpg

    Both channels sound fine and equal volume-wise but this balance control circuit isn't working properly.
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Balance control problem on Panasonic SG-999

    Can you upload the whole service manual?
    Are you getting 6.40V at the viper, it is a strange setup, instead of using ground as the ref point.
    Attached Files
    Last edited by budm; 10-10-2014, 05:18 PM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

    • jimkarl
      Member
      • Jul 2014
      • 37
      • USA

      #3
      Re: Balance control problem on Panasonic SG-999

      Originally posted by budm
      Can you upload the whole service manual?
      Are you getting 6.40V at the viper, it is a strange setup, instead of using ground as the ref point.
      Turned out it was a bad trace on the circuit board. Problem solved.

      Comment

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