# Stereo Memory Man Echo/Chorus Questions



## vadsy (Dec 2, 2010)

Picked this guy up today and I was hoping for some info or a manual and with the million versions under "Memory Man" it's a bit vast looking online so maybe someone here might have a few quick answers. 

Does it look stock or tinkered with? 
Why the bolt/nut on the bottom plate with nothing attached? 
Does the power supply seem correct? 
What should this unit be running for a supply, 24VDC centre positive?

Thank you.


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## vadsy (Dec 2, 2010)

Got some answers and I plugged it in but nothing works and the seller did mentioned that so I paid accordingly. I'm suspecting a true bypass mod gone wrong but I'm no engineer. Just wondering if someone could recommend a shop north of the border that could have a look at this for me.

Thank you.


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## Budda (May 29, 2007)

Maybe send a gut shot pic to scott at ask and ye shall receive, maybe he'll see something out of spec?


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## mhammer (Nov 30, 2007)

I was initially confused by this, thinking it was much older. But I found the schematic for it in my collection. It was in PDF form, so there is some detail lost in the graphic conversion for posting here.

At first glance, there does not appear to be anything blown. And yes, the power supply is appropriate. Let us hope the delay chip itself is fine, because those buggers are hard to get hold of, and expensive when you do. Fortunately, there are other *much* cheaper, and more available, chips on the board that could also be a source of non-functioning. Let's hope the problem narrows down to one of them, if need be.

There are 3 trimpots on the board. Two are 100k and one, adjacent to the MN3005 is 5k. The 5k trimmer is for balancing out the two complementary outputs from the delay chip, and should be set near the midpoint, as it currently is. One of the trimmers is for setting the max delay level. The third trimmer is for setting the bias.

ALL delay chips require that the audio signal be sitting on a DC voltage in order to pass through the chip. Ifthat DC voltage is too high or too low, you won't hear anything from the delay chip. If it is close to, but not quite at, the optimal bias voltage, you'll hear a distorted lower-level delay signal. Ideally, one sets it using a scope, but it can be set by ear. If the bias is off, set the blend for max delay, delay time at max, and zero Feedback (no Chorus), and gradually adjust the trimmer until you hear best signal quality. Don't worry about damaging the chip by over or under adjustment.

One of the most common mistakes made by novices is overheating the solder lugs on 3PDT switches. The connections are made to the "right" places, but the overheating has rendered the switch non-working. As ever, watch this video: for tips: https://www.youtube.com/watch?v=6uhDKFhqYnw


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## vadsy (Dec 2, 2010)

Mark,

Thanks for the reply. 

Nothing appears to be blown, caps look intact, and the unit is fairly clean but I get no power or sound of any kind. I metered the power supply and it seems good but the pedal is dead, or so appears. I bought it knowing it had a major malfunction and paid accordingly, truly the MN3005 was my prime motivator. My gut is telling me it might be a true bypass mod that went bad, just a second brief look tonight I found a broken solder connection on one of the jacks. I don't think it will fix the pedal but I'll try repairing it tomorrow.

I wouldn't mind seeing this thing working again but I know I can't fix anything beyond the obvious solder joint, popped cap or broken switch. I got in touch with Chip Scooter Dugan, he can't help. Howard Davis has not returned my email. Mike from Analogman also can't help but recommended David Morrin from Main Drag in Brooklyn. David replied right away and can help out, seems competent and knowledgeable, but I'd like to try the possibility of a Canadian fix, can you repair it? If I sent it to you would you have a look at it?

- - - Updated - - -

Budda,

I thought about Scott, I'll send him an email and see if he can help. Thanks


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## mhammer (Nov 30, 2007)

The MN3005 is socketed. Gently removeit from the socket, and see if you can find somebody in your area, perhaps via this forum, who also has a 3005-based pedal. That pedal will also likely have the same chip socketed. What you want to do is confirm that the 3005 is okay. If it is fine, then we can turn our attention to other things.

Once the 3005 is safely extracted, I'd suggest powering up the pedal, and measuring the voltages on the various other chips. The voltage should be measured from pin 8 on the 4558 chips, from pin 7 on the 5534, and from pin 13 on the 570. Naturally, your other meter probe goes to ground. The 4047 will tend to fry when receiving >15V. And since the 4047 is the clock that is required to step the delay chip through its paces, if the 4047 is shot, then the delay side won't work.

But the absence of even bypass sound, using TB, strongly suggests that the installer used too much heat, and buggered it up. I demonstrate, in the Youtube video, how too much heat can render stompswitches nonfunctional. It IS possible to nondestructively take the stompswitch apart, clean the contacts, and reassemble it. When I consider the suggested "failure rate" on these things amongst DIY-ers, no manufacturer could stay in business very long if what they were selling to major (e.g., EHX) and mid-level (e.g., Keeley, Earthquaker) manufacturers caused that many problems. So the issue is not the switches themselves, but inappropriate or lackadaisical soldering techniques that undermine he switches. I've messed up, and repaired, enough of these puppies to be confident in what I'm saying: you CAN restore functionality to the switch, and the problem MAY simply be that the goop inside that was supposed to serve as dampening and lubrication is now serving as unintended insulation.


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## vadsy (Dec 2, 2010)

I follow what you're saying, testing the 3005 chip should be first priority and I can do that using my AD-80. I'll get it pulled apart and tested, if it doesn't work this pedal can probably go in a drawer for long term storage.

I'll do my best to get some voltage readings, especially from the 4047 chip.

Can I ask regarding the true bypass, I agree that if no sound is coming through with the TB on/off something was either messed up or done wrong, correct? Can you tell, using the pictures, that the wiring is correct and I either need to fix the switch or replace it? The schematic is a little too small and blurry to be of use so I can't tell. Maybe I should unsolder and meter the existing installed one or grab a new switch and start fresh but I couldn't do that unless I knew the current wiring was correct.


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## mhammer (Nov 30, 2007)

The simplest test here would be to skip the stompswitch for the moment, and send the input wire to the input jack, and output wire to the output jack. No bypass, but you'd know it the circuit itself was working.

Usually, when I'm building stuff, I'll wire things up this way, and leave wiring in the bypass switch until after I know everything else works as intended.


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## vadsy (Dec 2, 2010)

That is a good idea, will try, thank you.


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## vadsy (Dec 2, 2010)

Finally got around to pulling the chip and trying it in a working AD-80. I'm happy to report it fires up and sounds great. Just need to get passed the true bypass mess and I could have a working pedal that's fairly cool. Thanks for the suggestion, mhammer.


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## bduguay (Jul 15, 2009)

Let's re-visit this one because I have it here and I've made some progress. I have it passing signal now and you won't believe what the problem was.
If you look at the 3rd pic from the top you'll see all 3 tabs of the jacks poking out just a little. See the way they're oriented? When a plug was inserted the tab bent back far enough to ground out to the chassis. A simple 20 degree or so rotation to the right and all is good. Now, Vadim is correct, I've confirmed that the compander, BBD, and clock chip are okay. It passes signal but no echo. I'm getting signal out of pin 14 of the compander but nothing from
10/11. I've tried different companders but still nothing yet they all test fine in my aqua puss clone.
Also, the LED is fried and while there is definitely power where the above pic shows the red wire connecting to, the black spliced-to-white wire is going to a spot on the board where R59 is on the schematic and a 1N4148 diode (D6 silkscreened on the board) that is not shown on the schematic. I'm approaching wits end on this one. Care to join in on the fun Mark?
B.


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## bduguay (Jul 15, 2009)

Problem solved.
Pedal is working.
Carry on.
B.


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## mhammer (Nov 30, 2007)

Just catching up here. For my own benefit, and hopefully that of others, where was the weak link?


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## bduguay (Jul 15, 2009)

In an effort to make myself feel less of a failure, I replaced the non-functioning LED (DED) with a new LED so at least that part of the repair would be complete and darned if the thing didn't suddenly work. Now, I've shown the schematic to a couple of more learned colleagues and they both agreed that it shouldn't have made any difference either way. I dunno you know?
B.


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## vadsy (Dec 2, 2010)

Have to say thanks to Brian on fixing the Memory Man.

Great guy to deal, thank you.


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## bduguay (Jul 15, 2009)

vadsy said:


> Have to say thanks to Brian on fixing the Memory Man.
> 
> Great guy to deal, thank you.


Oh thank you!
Did it arrive okay?
B.


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## vadsy (Dec 2, 2010)

It arrived just fine. Mail dude rammed it in the box so hard, he truly committed to the dunk, bent the whole thing. He must have known what he was carrying and couldn't contain his excitement or ring the door bell. All good though. 

rammed it in the box so hard, sounds like the start of a great dirty joke


Sent from my iPhone using Tapatalk


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## limelight65 (Jun 2, 2014)

you're in sherwood park? Call Linsey at Edmonton audio works in west edmonton.


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## vadsy (Dec 2, 2010)

limelight65 said:


> you're in sherwood park? Call Linsey at Edmonton audio works in west edmonton.


To share in my celebration? I'm sure its small potatoes compared to his regular day dealings. 


Sent from my iPhone using Tapatalk


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## vadsy (Dec 2, 2010)

limelight65 said:


> you're in sherwood park? Call Linsey at Edmonton audio works in west edmonton.


I actually did contact Linsey some time ago about fixing this thing but he said he couldn't help out. He did just recently get my brothers Hammond C2 going properly.


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