Home › Forums › Vintage EHX › Electro Harmonix Electric Mistress repair (polarity fry?!) – hints or tips required!

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  • February 18, 2015 at 6:30 pm #120545
    beatnik
    Participant

    i have placed LM741 instead of TL071 and now the pedal works properly again

    October 17, 2015 at 9:08 pm #120942
    Don X
    Member

    I seem to have the same problem after hooking up a power supply.
    This happened before the internet, and it clearly states on the pedal “AC”, so I’ve assumed alternating current and that polarity was irrelevant.

    Hopefully through these pages I can fin a fix; since i recall the old pedal had a lot more dynamic and raw edge compared to my new de-luxe.

    mistress mk1_zpsyhr4cijj.jpg

    October 18, 2015 at 12:23 pm #120944
    Scruffie
    Member

    If you plugged in AC power rather than DC it needs to go to a tech, AC can be very destructive and anything active, diodes and electrolytic caps will all need checking, it’s not a simple fix job.

    October 18, 2015 at 12:40 pm #120945
    Don X
    Member
    Quote:
    If you plugged in AC power rather than DC it needs to go to a tech, AC can be very destructive and anything active, diodes and electrolytic caps will all need checking, it’s not a simple fix job.

    I see from this thread that a few EH pedals had AC power, and my mistress is clearly marked AC over the power jack- perhaps someone could enlighten me on this. It’t he same as OPs pedal so will check the board first.

    October 18, 2015 at 12:43 pm #120946
    Scruffie
    Member

    The AC refers to the adapter that would have originally been used with it which supplies 9 or 18V DC depending on the model, trust me, you’re lucky it still works at all (unless you did actually use DC).

    October 19, 2015 at 12:39 am #120947
    Don X
    Member

    put the meter on the diode and no current passing either direction.

    eh comp_zpsatrgtox2.jpg

    EH PCB_zpstock74ue.jpg

    Code:
    http://i.imgur.com/Zror2i5.jpg -hi res
    Code:
    http://i.imgur.com/DKdk29b.jpg -hi res
    October 19, 2015 at 1:15 am #120948
    Scruffie
    Member

    Check the voltages on all the ICs and post them.

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