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BIC D-121OR Powered Sub Auto-on not working

Discussion in 'Electronic Repair' started by Todd, Feb 10, 2007.

  1. Todd

    Todd Guest

    I am looking at this powered sub because it wouldnt turn on anymore, fuse
    was blown. Opened it up, and 2 6800mF 63v caps where blown. Checked the
    diodes and bridge they both checked out good. Put 2 new caps, and turned it
    on with no audio being feed to it. The green power light comes on when the
    switch is set to "on". When you put the switch to "off" a 24v relay goes
    nuts, cycling at like 10hz. When you switch it to "standby" somes the relay
    goes nuts and sometime it just turns on. When the switch is in "auto" the
    amp should go into standby mode when no audio is detected, when in "off" it
    just always be in standby mode. I noticed this unit has a 2SD669A / 2SB649A
    pair and the resistor to the 2SD669A that feeds the emitter is a little
    black. I traced it and it goes through a zener, and hooks the the emitter
    of the 2SB649A? My question is how do they interact in a circuit together?
    And would this cause the problem that I am having? Should there be
    something else I should be looking at?

    Thanks for any info
     
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