Home › Forums › Help/Technical Questions › Older EH Memory Man Not Working – Any Ideas?

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  • February 11, 2009 at 1:20 am #77722
    megachunk
    Member

    Hi All – New to the board.

    I have an old Memory Man black and blue case on my bench to repair, not working. I’ve removed the power trannie and it tests fine. I am replacing the 3 power caps, one was popping out. The footswitch makes a pop through an amp, but no delay or chorus or dry signal is passed through. If anyone has had this dilemma and been able to fix it, I sure would be appreciative. Chip out maybe? A schematic to look at would be great, too. If any of you can point me to a website that may have this info, I’d be very grateful.

    Thanks in advance.
    Megachunk

    February 11, 2009 at 1:29 am #93056
    The EH Man
    Moderator

    Which one do you have? See this link:
    http://electroharmonix.ronsound.com/index.php?option=com_content&task=view&id=30&Itemid=45

    February 11, 2009 at 1:41 am #93058
    megachunk
    Member

    It’s the black graphics with blue writing and the ECHO/CHORUS switch.

    Thanks for the reply!

    Mega

    February 11, 2009 at 1:48 am #93059
    The EH Man
    Moderator

    Assuming your power supply is working correctly and you have +15 and -15, I’d replace the first op-amp because that’s where your bypass signal comes from. If your power supply is bad, replace the NE5554 IC w/ a couple of 3-legged voltage regulators.

    February 11, 2009 at 3:08 pm #93083
    megachunk
    Member

    Thanks a whole bunch, Ron.

    Power supply’s fine, getting about 17+/- replaced the larger electrlytics. Gonna do the op amp today, but not sure how to do the voltage reg thing if I’m having to. Any particular value for those regs? Or would you by chance have a diagram of this mod?

    Sorry for all the beggin’. You’ve been an immense help already.

    Thanks again
    MikeG
    Megachunk

    PS: I work at Lace Sensor – If there’s any pickups you’d like to try out, give me a holler over there.

    February 11, 2009 at 3:27 pm #93085
    The EH Man
    Moderator

    Sounds like your power supply is OK. The op-amp may do the trick for you.
    It’s really not that complicated for replacing the NE5554. Just a matter of matching pins up with a couple of 15v regulators. If you really need to replace it I’ll post the details here for you and others.
    If you can, while you have it apart attach a heat sink to the NE5554. Might make it last longer and you may never need to replace it.

    February 11, 2009 at 5:49 pm #93094
    megachunk
    Member

    Ron.

    I’ve replaced the bridge rectifier as well, but which op amp is the first in the chain? Below the top pot or bottom pot? The one closest to the power caps I’m assuming.

    Thanks again.

    Mike G.

    February 11, 2009 at 6:06 pm #93097
    The EH Man
    Moderator

    I don’t have the schematic in front of me but you can follow the input jack lead in across a cap and/or a resistor and find where it goes in to the 1st op-amp stage.

    February 11, 2009 at 7:25 pm #93107
    megachunk
    Member

    Thanks, found it.

    Put a low noise op amp in and didn’t really do anything. Not getting any output or signal through, with the switch in either position. I also have a few compensated op amps I could put in. I may go and replace them all.

    Thanks again.

    MikeG.

    February 11, 2009 at 7:33 pm #93109
    The EH Man
    Moderator

    Before you do anything else, audio probe (or ‘scope) the op-amp output to see if anything’s coming out. Might be a bad footswitch after all.

    February 11, 2009 at 7:58 pm #93114
    megachunk
    Member

    Alas I have no scope or injection amp.

    I did swap out the switch and nothing doin’. Actually, no click thump now unlike the other switch- that one had definite thump through the amp.

    I’ll go through the works soon – Have to put it down for a while and get back to it later. I truly appreciate the info you gave me.

    MikeG

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