No sound from MXR Micro Distortion Pedal project

[jfd986]

Hello everyone. First post, will try to be concise.

MXR Micro plus distortion clone
2.http://www.tonepad.com/project.asp?id=2
3. I bought a pre-made PCB off the internet, bought all the parts from an online electronics supplier in Canada (Digikey), and I even asked tonepad if a 500k log pot would do the work of a 500k rev Log Pot as long as I wired it in reverse, and they said it would.
4. I used a Log pot as mentioned above for substitutions, but I initially also placed the OpAmp in the socket I soldered in the wrong orientation. My buddy said I "probably fried the opamp" so then I ditched it and used another of the same model, in the correct orientation. I have a third as a spare. I used n4148 diodes and placed them according to the polarity indicated in the guidelines. No other mods, and the initial opamp positioning was a mistake so I can't really count that as a mod, I just mentioned in case it may have been relevant.
5. It is negative ground as far as I know. I only wired it for plug-in with a 9v dc adapter, there is no battery clip.
6. It lets zero sound through, and I don't have an LED wired in so I don't know whether or not I'm getting power. However, when the footswitch is pressed, there is some sort of noticeable change in voltage somewhere as measured with a multimeter.

The DC 9V adapter works perfectly with my other pedals, no problems with it as far as I know, it is my primary adapter.

1.



2.Checked the forum, and most of the questions regarding this pedal appear to be about mods. I honestly just want the regular thing that I'm hoping I built, to work.


I know nothing about any of this. I built one successful pedal but it was from a BYOC 808 Overdrive clone kit, and I think a couple wires were touching because a jack was loose. I also replaced a busted footswitch on an MXR micro chorus and then sold it after it was declared working by whoever was testing it. That's the extent of my troubleshooting. This is one of those builds where I tried to get the PCB and then buy everything from scratch to save money, so I'm hoping I can make this work because it'd be a big deal for me. Appreciate all your help, thanks in advance.

Glamour shots

[iainpunk]

welcome to the forum,
may i suggest you check this link:
https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

cheers, Iain

[jfd986]

I checked that post on debugging, and I actually tried to model my post around that post on debugging.

Would you be able to tell me what specifically (from that post) I would need to show you in order for you to help me?

I don't actually know anything about electricity or what is what, I just did the voltmeter testing (results included in the JPEG) and tried to include the details that the post was asking for in the first section of my post.

[Keeb]

Welcome!

You are feeding it 18,6V when the chip is rated for 18V max.
You should have 1/2 voltage at the orange track (9 volts in your case). It seems you have a lot of cold solder joints (for example the jack to the right in the third picture). Remove the ic and the diodes and reheat the joints that aren't shiny (on the board and on the jacks). No need to add extra solder. Power it with a 9V source and check voltages again. If that doesn't fix it, switch the ic and take new voltages!

[PRR]

Welcome.

> I checked that post on debugging, and I actually tried to model my post around that post on debugging.
Would you be able to tell me what specifically (from that post) I would need to show you in order for you to help me?

Clarify this:
"when the footswitch is pressed, there is some sort of noticeable change in voltage somewhere as measured with a multimeter."

Noticeable like 2V to 100V? Where is "somewhere"? One great thing about electricity is ease of measurement. And cuz electrons are invisible, we NEED those meter numbers to even guess what's gone wrong. Do you need a link to a meter-reading tutorial?

[iainpunk]

I checked that post on debugging, and I actually tried to model my post around that post on debugging.

Would you be able to tell me what specifically (from that post) I would need to show you in order for you to help me?

I don't actually know anything about electricity or what is what, I just did the voltmeter testing (results included in the JPEG) and tried to include the details that the post was asking for in the first section of my post.

i just now realized that the numbers in the image are the voltages, which i initially ruled out because "9v - 18.6" confused me.
also, the IC voltage readings re confusing try to use the ''insert ordered list'' on top of the text editor box to denote which pin has how high of a voltage. (the one above the 'icon frown' and 'icon idea')

this makes it easier for us to decipher your problem.

that 18.6V seems ridiculously high, and the IC is probably fried.

cheers, Iain

[jfd986]

https://www.digikey.ca/en/products/detail/w-rth-elektronik/694106301002/5047522

That's what I bought. Could that be part of the problem? I thought if the wall adapter was 9V then I'd be fine, is that not the case?




That's the wall adapter I used.

If I got a different jack, would this prevent the whole 18.6 V business? Asking because I'm somewhat convinced (because all my 9V pedals work with this adapter) that it's not the power supply, and idk how else I could be getting 18.6 V.

If I order a new jack, one that's "rated" for 9V perhaps, I will still be resoldering the cold joints, thanks for that learning point there. I had to google that, but it made sense after I did because halfway through this project, I junked a $20 amazon iron because it was taking too long and the tip got ruined, and I went to A1 electronics here in Toronto and bought a proper soldering iron for $49 ("proper" for me) and the difference was immediately noticeable

[duck_arse]

You are feeding it 18,6V when the chip is rated for 18V max.

the lowest spec LM741 is rated at +18V and -18V at the same time - a 36 V potential difference. +18V won't make it sweat.

as for the power adaptor, measure the voltage on the plug itself, unconnected to pedal.

and welcome.

[iainpunk]

does Canadia have 120v or 230v comming out of the wall?

cheers

[PRR]

If he were feeding double-voltage from the wall, there would be smoke.

[iainpunk]

If he were feeding double-voltage from the wall, there would be smoke.

doesn't have to be, if it uses capacitors and a regulator that is rated high enough, it could be totally fine, the transformer would probably clip the wave form to heck tho, due to saturation. this would also limit the voltage.

cheers, Iain

[jfd986]

Okay so Canada has 120 coming out of the wall. I did the measurement of the adapter and with the black lead in the center and the red lead touching the outside, it reads "18.6" as voltage. So I guess that means I potentially haven't toasted my opamp if they're rated for 36 (+18/-18) and I should just melt my cold joints?

[duck_arse]

interesting. all the mentions of specifications for that adaptor I glanced towards said something like "9V DC 5% regulation". I wonder what they meant.

do you have any power resistors you can load the supply with, to measure the loaded out volts? between 60R and 100R, at least 1 Watt .....

[jfd986]

I don't have any electronic parts other than what I used for this build, one spare IC, and then some stuff for the fuzz pedal build I plan to start as soon as this one is done.

Yup, optimist.

I'm gonna reflow the cold joints today to tomorrow, will post if anything changes.

[jfd986]

Okay, reflowed everything, still no joy here.

https://youtu.be/-QZ3-SYhtD4

This is a three minute video, of basically me just plugging it in and trying to run it, nothing seems to be happening whether or not I push the footswitch, I think I commented earlier that something was happening but I must have been mistaken.

I guess let me know if, at this point, I should try switching out the IC, or if anyone has any other ideas? Thanks, and thanks for the welcome wishes.

[khm9]

Since you're not getting any sound even with the circuit bypassed, something is probably wrong with your wiring.

Make sure your input and output jacks are wired correctly.

Also, consider simplifying the build for now.
Wire the jacks directly to the PCB- omitting the switch.
Once you get the circuit working only then worry about the rest of the wiring.

[jfd986]

I'm not quite sure how to wire the jack directly into the PCB, but I think I found something that might be wrong here.




Not sure if everyone can see it but I think that that outermost diode has a lead that is sticking out of the socket, because when I snapped those sockets I think one of them ended up more broken than I thought it was. I don't really know if that lead is still sufficiently contacting the board through the socket so I think I'm going to remove those sockets and solder the diodes directly into the board and try again.

[iainpunk]

you can use the beep function on a multi meter to test for continuity, from the top of the diode lead to the solder pad.

cheers, Iain

[jfd986]

Since you're not getting any sound even with the circuit bypassed, something is probably wrong with your wiring.

Make sure your input and output jacks are wired correctly.

Also, consider simplifying the build for now.
Wire the jacks directly to the PCB- omitting the switch.
Once you get the circuit working only then worry about the rest of the wiring.

I re-wired without the switch, and it still doesn't seem to be working. I uploaded a YouTube video of the pedal here with the current wiring.

https://youtu.be/BTMEqps1WzU

If you still believe it's a wiring issue, what would you recommend?
Here are some pics of the off-board wiring I have going right now:






- Sleeve of input is going to GND + fat terminal of 9v socket + sleeve of output
- Tip is going to input of effect





- Tip of output is going to PCB OUT

Thoughts?

[iainpunk]

2 things to help you/us

the DC voltages in the opamp, using the conventional number system


and you might want to make yourself an audio probe to trace where the signal reaches, and where it stops.


the fact there's 18v on one of the opamp pins worry's me a little, some opamps can't handle higher voltages.

in this picture, the opamp is in the socket 180 degrees the wrong way as well:


cheers