Simple envelope, I built two, one is acting up


I built a module containing two of the simple envelope stripboard layouts.
One works OK.
The other one, I built exactly the same, at the same time and the gate stays open.

There is no schematic on the page so I am a bit lost.
I disconnected the manual switch and the Led, no change, so they are wired fine.
I disconnected the input jack, no change.

Does anyone have a schematic for it?
What could cause it? I’ve been staring at the board for hours, going over the traces. Maybe a faulty diode?

Thanks for the help!

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Thanks for your help, I did all that, I always power my modules without ICs to check the various voltage supply points.
I have inspected all traces with a loupe and scraped the gaps with a blade to ensure there are no shorts.

I am really looking for input about the circuit, a schematic, or an explanation of which part could cause the output to remain constantly up.


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Stripboard often fools me and i can take an age to find which hole I’ve missed. Post a side by side photo so we can all have a go at spot the difference. The thread @analogoutput posted is a great fault tracking start.
Can you post a link to the diagram you’re using?

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Yes, this is the layout:

I really wish there was a schematic on the page.
I’ll be right back with pictures.

Alright, it’s gonna be a little hard to see what’s what but here is the circuit that works:

And here is the one that does not work:

And here is the faceplate

Notice the pots are in opposite positions on each build, and the power supply it’s own little portion of the board and is then wired to both circuits.


What it tried:

Disconnecting everything from the center pin of the mode switch.
Disconnecting the LED.

I’ve been over the board several times, hopefuly someone will have sharped eyes.
I will reprint the layout in the morning and draw over all the traces again, but I am pretty sure I built it right, I did both at the same time…

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maybe test another IC and check resistor value again

also are you sure that’s no bad connection here


Haha yes it looks insane but the power side is ok.
Good eye on the other spot thought, i will definitely check it tonight.


Think this is right


Thanks for the schematic!

It really helped, I found my short :wink:


Hello everyone! :slight_smile: I hope you are all doing great ! I am posting here because I am facing an issue with the simple envelope circuit, designed by LMNC.

I’m a beginner so I focused on the basic envelope design (no push button just Attack, Release, Gate, CV out). I finished the build but for some reason the envelope cv out goes negative whenever I dial the release parameter almost all the way down.
Do you think this is normal? When I plug my Neutron’s ADSR into the oscilloscope, it never returns negative values.

Do you think you could have a look please?

I add pictures of my build so that you can have more information on this issue.

Here is the weird signal:

A few pictures of the build:

I thank you all in advance for your help or comments :slight_smile: have a great day.
(also this is my first post so you can let me know if this needs to be moved somewhere else, I did not want to start another thread)

I don’t see how that can happen if it’s built right. There’s a diode between the buffer op amp and the output (and resistor to LED). If the capacitor voltage is negative then current cannot flow backwards through the diode, so there can be no voltage drop across the load to ground, so the output must be zero volts.

Furthermore the capacitor shouldn’t be charging quickly up to a negative value. The incoming trigger should charge it quickly to a positive value, and then it’ll decay to about -10 V, but it shouldn’t charge quickly up to that.

So I’d say something’s wrong with your build. See:

Since you have a scope, check directly:

  • Voltage on the capacitor, should shoot up to (about) +10 V and then decay to -10 V
  • Voltage on the op amp pin 1, should alternate between (about) +10 V and -10 V

You did plug it in, right?

Hi and thank you very much for the detailed reply!

Yes the module is powered on, on the picture (I had this other cable sticking out of the case which made everything confusing sorry). I checked the circuit many times and found nothing wrong.
I recalibrated the oscilloscope just to make sure but this negative voltage still occurs when the release is at 0. As visible in the pictures below, when the release is not at 0, the signal goes to the negative territory as well but at -0.48V only, this issue is more dramatic when Rel = 0.

Release !=0

Release =0

I need to check the “General advice” you included in your response.
Meanwhile, here are the results of the tests you suggested with the oscilloscope:

As you can see, the values I get differ from the ones expected.

Again many thanks for your help ! have a great week-end :slight_smile:

OK, I finally noticed your scope input appears to be AC coupled. That’s what “AC” on the bottom line signifies, yes? You want DC coupling. Switch to that and take another look.


Thanks ! it works well ! that’s a lesson learnt on properly setting up my oscilloscope I guess