Home › Forums › Help/Technical Questions › memory man stereo echo/chorus whine!

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  • September 23, 2009 at 12:52 am #79019
    looptheloop
    Member

    hi. picked up a (90’s reissue, according to ehx man here) memory man stereo echo/chorus. fantastic pedal. love the memory boy which i also have. this seems to really excite my sound, not as dark as the memory boy, BUT just wanted to know why when i push the delay past about 2 o clock there’s a high-pitched whine, quite noticeable. sometimes it goes away for a while, but its pretty constant. have i got a dud? thanks

    September 23, 2009 at 1:58 am #101683
    The EH Man
    Moderator

    That’s likely clock noise from the delay ICs. You can adjust the balance trimpot on the board to minimize it but it’s difficult to completely eliminate it.

    September 23, 2009 at 1:58 am #101684
    Fender&EHX4ever
    Moderator

    It probably needs a trimpot alignment; otherwise, if you have a 10 Band Graphic EQ, you could probably pull it out around 16kHz.

    September 23, 2009 at 4:06 am #101688
    looptheloop
    Member

    thanks for that. haven’t opened it up yet but is there only one trimpot? any ideas on how i adjust it (clockwise for less whine :)? – cheers.
    also, can anyone tell me what the trimpots (2 of them?) do on the memory boy?
    thanks to ehx for great products

    January 26, 2015 at 3:12 pm #120479
    wildziak
    Member

    Hi guys! Sorry for bringing to life this old thread but I’m in desperate need of your help!

    I have all the required equipment ( oscilloscope and all the necessities ) and experience with fixing the pedals etc

    I have vintage 3 knob Memory Man Solid State Echo/Chorus version loaded with MN3005.

    Problem is that it has substantial noise (more like high-pitched whine ) added to the signal. As I understood from reading tons of threads this is most likely a clock noise.

    The schem is below

    http://img163.imageshack.us/img163/5990/memorymanschem.gif

    I tried adjusting all 3 trim pots with a use of oscilloscope but that didn’t help at all… I used these instructions:

    http://www.madbeanpedals.com/forum/index.php?topic=16660.0

    adjusting Clock Balance trim changed clock noise only slightly…

    Please help

    I’ve check voltages on each op-amp and chip, here they are:

    A1
    0
    0
    0
    -14.85
    -5.5
    -5.8
    -5.8
    14.85

    A2
    0
    0
    0
    -14.85
    0
    0
    0
    14.85

    A3
    -10.22
    -10.22
    -10.22
    -14.85
    -5.1
    -6.66
    -10.21
    14.85

    MN3005
    0
    -7.4
    -6.68
    -7.43
    -14.85
    -7.45
    -6.61
    -13.67

    CD4047BC ( My version has BC instead of BE )
    -14.60
    -0.22
    -10.51
    0
    0
    0
    -14.85
    -14.85
    -14.85
    -7.44
    -7.44
    -14.85
    -14.60
    0

    instead of NE5554N I have L7815CV and L7915CV, so here are voltages for them:

    L7815CV:
    14.85
    0
    16.31

    L7915CV:
    0
    -19.3
    -14.85

    Please help! What should I do to get rid of clock noise? Maybe some of the chips went dead? Any ideas?

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