Home › Forums › Help/Technical Questions › Memory Man Solidstate Echo/Chorus noise

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  • January 27, 2015 at 7:46 am #83806
    wildziak
    Member

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

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

    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

    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

    January 27, 2015 at 12:03 pm #120486
    The EH Man
    Moderator

    That’s pretty much the nature of the beast. Set it on maximum delay and minimize the noise as much as possible. You might also try replacing the balance trim with a multi-turn trimpot of the same value. That will allow you to really zero in on the quietest spot.

    January 27, 2015 at 12:34 pm #120487
    wildziak
    Member
    Quote:
    That’s pretty much the nature of the beast. Set it on maximum delay and minimize the noise as much as possible. You might also try replacing the balance trim with a multi-turn trimpot of the same value. That will allow you to really zero in on the quietest spot.

    Thank you, EH Man.

    I’ve tried once again but the best I managed to get was a saw wave signal about 0.9 V (peak to peak) and frequency ~ 6250Hz

    And that’s quite noticable when I play…

    Any other suggestions?

    I’ll try to replace balance trimpot with multi-turn trimpot, but I’m not sure it will help a lot.

    January 28, 2015 at 10:27 pm #120488
    wildziak
    Member
    Quote:
    That’s pretty much the nature of the beast. Set it on maximum delay and minimize the noise as much as possible. You might also try replacing the balance trim with a multi-turn trimpot of the same value. That will allow you to really zero in on the quietest spot.

    Hi again, EH Man! I’ve installed bourns 10kOhm multi-turn trimpot but adjusting it still made nothing…I still get the same results. Maybe I should look somewhere else for a problem? Thank you so much for help!

    January 29, 2015 at 9:48 am #120489
    wildziak
    Member

    Could it be that MN3005 or CD4047BE went dead? Cause that freaky saw wave on 3 and 4 refuses to get lower no matter how accurately I set clock balance multi-turn trimpot…

    Arrrrgh! Help me pleaaaase!

    January 29, 2015 at 11:38 am #120491
    Scruffie
    Member

    If it delays, the 3005 & 4047 are fine.

    As EH Man said, nature of the beast that it whines, no companding circuitry and not that great low pass filtering. You can try adjust the high pass trim to get rid of it.

    I think what you have might just be normal behaviour, if you don’t want whine you should probably look to a Deluxe Memory Man.

    January 29, 2015 at 12:06 pm #120492
    wildziak
    Member
    Quote:
    If it delays, the 3005 & 4047 are fine.

    As EH Man said, nature of the beast that it whines, no companding circuitry and not that great low pass filtering. You can try adjust the high pass trim to get rid of it.

    I think what you have might just be normal behaviour, if you don’t want whine you should probably look to a Deluxe Memory Man.

    Problem is that when I’m adjusting highpass trim number of repeats decrease significantly…Ah guess I’m powerless here.

    Thank you guys anyway…

    If you have some more advice or suggestions I would be glad to hear you

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