Home › Forums › Vintage EHX › Questions about vintage Memory Man Solid State Echo Chorus repair w/pics

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  • April 18, 2020 at 2:04 pm #86226
    SurfGreenTele
    Member

    Hey guys, I just got a non-working vintage Memory Man SS Echo Chorus and I have a few questions. I’m getting no sound at all going through it, whether bypassed or engaged – so would that most likely indicate a power supply problem?

    It is an odd export model with no internal transformer – instead an 1/8″ power jack taking a 24VAC 1000ma wall-wart (not DC). I tested the wall wart on my multimeter and found I was getting no voltage at all from it…so I presume and hope that’s the only issue.

    Also, the old 1/8″ power jack was kind of mangled and loose, so I decided to swap it for a 2.1mm barrel style that I had laying around. Then I ordered a new Triad 24VAC 1000ma wall-wart with a 2.1mm barrel plug (has not arrived yet).

    Just wondering, does polarity not matter with the wires going to the jack being that it’s AC and not DC? Right now I have the wire with series resistor to pin 2, ground or neg (?) wire to the center pin. Let me know if I should swap them. 😮

    [img]https://scontent.fyhz1-1.fna.fbcdn.net/v/t1.0-9/93719958_10156915536796283_3617360437537931264_n.jpg?_nc_cat=110&_nc_sid=0be424&_nc_ohc=Z1pkykokpskAX_lSUSq&_nc_ht=scontent.fyhz1-1.fna&oh=2739d2a1c8a69dba9fd7bcc10efb4274&oe=5EC1CA52[/img]

    [img]https://scontent.fyhz1-1.fna.fbcdn.net/v/t1.0-9/93643941_10156915529091283_7265565324446007296_o.jpg?_nc_cat=104&_nc_sid=e007fa&_nc_ohc=KhQDQ9IiubYAX-loeKd&_nc_ht=scontent.fyhz1-1.fna&oh=bcafa9907c7ebaac2b4a3fcd004b6859&oe=5EBF122B[/img]

    [img]https://scontent.fyhz1-1.fna.fbcdn.net/v/t1.0-9/93857563_10156915529076283_119203772168667136_o.jpg?_nc_cat=111&_nc_sid=e007fa&_nc_ohc=fhz4loVlVzkAX8ddEwB&_nc_ht=scontent.fyhz1-1.fna&oh=d647c959b2efc299ef8c2739b061a419&oe=5EC1F3EA[/img]

    Power supply on order:
    [img]https://scontent.fyhz1-1.fna.fbcdn.net/v/t1.0-9/93714022_10156915528981283_1609061380927782912_o.jpg?_nc_cat=104&_nc_sid=e007fa&_nc_ohc=w83KGnrTzLEAX–3Kz_&_nc_ht=scontent.fyhz1-1.fna&oh=8b505c27433c400df2a484d4f78f07a0&oe=5EBFC42F[/img]

    April 18, 2020 at 2:11 pm #126004
    SurfGreenTele
    Member

    Also…I did a dumb thing yesterday – at first not realizing it took AC, I had hooked it up to a regular 24V DC power supply and got some odd faint squealing noises but still no guitar signal going through. I hope I didn’t kill anything. I know the other way is more dangerous (using AC on a DC pedal), but argh. :(

    April 19, 2020 at 10:39 pm #126009
    Scruffie
    Member

    No sound doesn’t necessarily mean a power supply problem, no, but as you tested your supply and had no voltage you’ve answered one question yourself :) this unit does require power for bypass.

    AC doesn’t have a polarity, but DC does, but hopefully the rectifier diodes will have provided some polarity protection.

    April 20, 2020 at 2:32 pm #126010
    SurfGreenTele
    Member
    Quote:
    No sound doesn’t necessarily mean a power supply problem, no, but as you tested your supply and had no voltage you’ve answered one question yourself :) this unit does require power for bypass.

    AC doesn’t have a polarity, but DC does, but hopefully the rectifier diodes will have provided some polarity protection.

    Thanks a lot for the input. Someone on The Gear Page suggested to check the regulator (NE5554N) next, if the new power supply doesn’t solve it.

    April 20, 2020 at 2:55 pm #126011
    Scruffie
    Member

    They certainly can and do go bad but thankfully be replaced quite easily with more ‘modern’ regulators.

    There’s a lot more that could be wrong before jumping to that though, could also be nothing wrong apart from the bad wall supply.

    In the mean time if you want something productive to do, you could test all the electrolytic & tantalum capacitors for shorts with the continuity setting of your multimeter (assuming it has one).

    April 20, 2020 at 6:31 pm #126012
    SurfGreenTele
    Member
    Quote:
    They certainly can and do go bad but thankfully be replaced quite easily with more ‘modern’ regulators.

    There’s a lot more that could be wrong before jumping to that though, could also be nothing wrong apart from the bad wall supply.

    In the mean time if you want something productive to do, you could test all the electrolytic & tantalum capacitors for shorts with the continuity setting of your multimeter (assuming it has one).

    Thanks, I will do that!

    April 22, 2020 at 5:49 pm #126018
    SurfGreenTele
    Member

    I’m happy to say, all is good with the new power supply!

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