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need some help repairing a Jamo SW 3015 active sub please

Discussion in 'Power Electronics' started by khalidlib, Sep 10, 2021.

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  1. khalidlib

    khalidlib

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    Sep 10, 2021
    hello everyone i am new to this forum, came here as per the advice of some friends, hoping to find some help repairing an active sub woofer i have for more than 10 years now, it is the Jamo SW 3015 active sub woofer with THX dedicated input , it was in storage for about 3 years since i moved to a new place, and i decided it is time to put my home theater back up ,however after bulging it in the sub and hooking it up to the amplifier pre out it did not make any sound , the on standby light came on but no sound with a faint buzzing sound coming from the amplifier plate, i turned it off and back on again and same story, then the on indicator light went off still the buzzing noise is their, like a small running fan blade hitting a small wire, i took the plate off but there was no fan and the noise is coming from the preamp board or the power supply unit , can't tell for sure but if i disconnect the power from the supply to the amplifier unit the buzz stops, all caps look ok and no burn marks anywhere, after asking around it appeared it was the capacitors at the hi voltage mains input , changed one and the buzz went away, i ordered a better quality and i will put them in when they arrive, sadly that did not fix the subwoofer
    still no sound and the indicator led would not come on, i left no stone unturned, looked everywhere for schematics and could not find anything as far as my knowledge goes apparently it does not go very far.
    i made a crude sketch of the connections and ics on the board for reference and i noticed a few things
    1- the 084C ICs on the small board get hot
    2- in the small board the continuity test between column A and column B is + except for the signal line there is no continuity
    3- it is printed in stencil on the board that Red line in column A is 12v but i could only mesure 6v
    4- the led terminal on the control board measure 2.6v when it is floating but when i connect the led to measure 0.6v
    so i am asking for help again please


    i am hoping someone with some knowledge or had a similar problem and fixed it could help me out no how to proceed to troubleshoot and fix the problem
     

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