Troubleshooting 3.0

7 years 7 months ago #556 by Ray
Troubleshooting 3.0 was created by Ray
Hi,

I guess you already did this:
www.electrosmash.com/forum/pedalshield-u...alshield-uno?lang=en
What do you get when you do:
2. Check the output stage: You can load the sine-wave generator program. It only uses the output stage independently that the input is wrong. If it works you can be sure that the second op-amp area is good. If not check for resistors placement, IC is the correct one? orientation?
Are you able to generate a sinusoidal waveform?

You can send us some pics of your pedal, sometimes there is something obvious that another pair of eyes could spot (our mail in the "contact us" scrolling down the website)

and then connect the output on my speaker box,

Do you mean a speaker or a guitar amplifier?

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7 years 7 months ago #559 by Ray
Replied by Ray on topic Troubleshooting 3.0
Thanks for the videos.
At the input of the circuit there is a potentiometer (white one) labelled VR1.
Did you try adjusting it?

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7 years 7 months ago #561 by Ray
Replied by Ray on topic Troubleshooting 3.0
The output stage is definitely working because you can generate sine waves without problems.
Its easier if you load the clean code because it should not add much noise or distortion to the signal.
The components and placement also look good... I would touch with the solder iron and a bit of solder all the joints to make sure that they are good and then with the multi-meter you could check the connections and resistors to see that all its all right.
Make sure that:
- You have 2.5V in both ends of R2.
- In the TL972 you have 5V on pin 8 and 0V in pin4
- In the TL972 without any input or output connected (just the pedalshield connected to the computer) you have around 2.5V in pins 5,6 and 7 (i read 2.1, 2.9, 2.9 in mine, just something around 2.5)

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7 years 7 months ago #564 by Ray
Replied by Ray on topic Troubleshooting 3.0

The capacitor number 6 is in the same node as the voltage divisor, when it should be connected between the 5V and the Ground seeing from the schematic point of view, I am just a bit confused cause in the layout design it seems to connect between 2.5V and the ground indeed.


You are totally right, I edited the schematic to make it easier to understand and I put the cap in the wrong rail, the original schematic looks like this:



So C6 decouples 2.5V and C11 decouples 5V.
Dont worry what you see its fine.


Can you check your 3PDT switch? it should work like this:
www.electrosmash.com/forum/pedalshield-u...shooting?lang=en#535
Attachments:

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7 years 6 months ago #566 by Ray
Replied by Ray on topic Troubleshooting 3.0

Alright, 3PDT foot switch sounds fine, the middle row is connected with the top row (taking the circuit from the building guide as reference).
Is it suppose to change if I rotate it 180 degrees? Making the bottom row connected with the middle row instead.


The 3PDT connects the middle row to the top row and when you click it, the middle row will be connected to the bottom row. The action is alternative connecting the middle to the top/bottom when you stomp it.

About the electrolytic caps, all of them should be placed with the white part (negative) facing "down", there is a white mark also in the silkscreen. From your pic they look right for me.

About the Jack... the pin 1 is the insider right? So its connected to the circuit while pin 3 and 2 are connected to the ground following the schematics.

The tip of the jack is signal (pin 1) and pins 2 and 3 are ground (the guitar is a mono signal),

In this image you can see the layout of top/bottom layers so it can help you for your troubleshooting:
www.electrosmash.com/media/kunena/attach...d-uno-pcb-layers.png

Tell me is you find something wrong.

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7 years 6 months ago #568 by Ray
Replied by Ray on topic Troubleshooting 3.0

Rendering Error in layout Message/Item: array_keys(): Argument #1 ($array) must be of type array, null given. Please enable debug mode for more information.

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7 years 6 months ago #571 by Ray
Replied by Ray on topic Troubleshooting 3.0
Hi, sorry for not having the native files inthe server. We updated them at some point and the link is broken. Today and tomorrow saturday I am away so I have limited access to the server, I will fix it the latest on Sunda

Your ADC seems to work fine, it is such a simple input circuit that I cannot see where the signal path is broken. It should go from the tip of the jack, go through the 3PDT, pass the cap and the resistor and enter into the opamp.

For a sigjal generator there is plenty of phones apps so you cand use your cell phone as a signal generator. I also use some free software to generate signals with your laptop sound card but I dont remember the name right now. There are plenty of free software for that.

If you have a multimemeter measure the resistor to make sure that they are fine and not broken, very rarely they can break as open circuits.

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7 years 6 months ago - 7 years 6 months ago #572 by Ray
Replied by Ray on topic Troubleshooting 3.0
The link to the native files is now fixed.
Sorry for the inconveniences caused:
www.electrosmash.com/forum/pedalshield-u...native-files?lang=en

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7 years 6 months ago #576 by Ray
Replied by Ray on topic Troubleshooting 3.0
Wow, amazing job!
Yes, there are 3 low pass filters with a cut frew around 5KHz, this freq looks a bit low but a lot of guitar pedals use this frequency because the balance between performance and sound is good.

So using your hand wired circuit and using the pedalSHIELD DUE op-amp and the arduino board with a similar circuit you have it working fine?
If its like this, there is only one posibility and its some bad solder joint or some extra solder going to the wrong place and connecting two undesired pins.
I am not sure about what equipment you have, I guess that you dont have an oscilloscope, otherwise is pretty easy to inject a signal in the input (using a cell phone signal generator app) and just follow the signal path till the signal disappears.

If you have a multimeter can you check one by one the pins of every component on the input stage and check that they are not grounded or soldered to the next pin?
To check this pins is important to do it on the top side of the board, sometimes the connectivity is broken between the top and the bottom side.
Also check that the pin A0 in the arduino board reaches the cap C1 (measured from the bottom of the arduino board to the C1 on the top side of the pedalshield board.)
More ideas:
- Try removing R1, it is not an essential component (it reduces pops) and may be causing some problem.
- You can link (solder a small piece of wire) between the legs of R5, it will transform all the input stage into a simple buffer and if it works like this (the volume will be lower of course because there is no gain) that will mean that the problem is around R4,R5, C3, C4, RV1.

99% of the time is just some joint or small silly mistake, and there is something in the input stage not working properly....

keep us updated with your progress.

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7 years 6 months ago - 7 years 6 months ago #579 by Ray
Replied by Ray on topic Troubleshooting 3.0
Again, nice work:

So I used the frequency of 3,3khz (above the cut off freq)

I guess that you meant below the cut frequency.

So, this are my ideas:
  1. Which signal level are you introducing with the signal generator? guitars are usually between 200mVpp and 1Vpp, depending your model and whether they are active or not
  2. When you check the level at the ADC input, the signal amplitude is the same as the input signal. The input op-amp has an adjustable gain (using RV1) between 1 and 21. Looking at your signals seems that you are working with unity gain, for guitar signals this is usually too low, the idea is to adjust is so the signal at the input of the op-amp has a peak to peak of around around 4V over 2.5V of offset. Are you aware that the
  3. I know that you are not a big fan of the 5KHz high pass filters, guitar signals dont have much info above that freqs and if you dont do this low pass filtering you end up having aliasing noise. 5KHz is a good balance between performance/sound, Boss uses 5KHz 3rd order Sallen&Key filters in some pedals and MXR does something similar. Anyway, if you want to experiment and you want to let more freqs through the filter, you can add some caps (10nF?) in parallel to the 68nF and remove the 270pF cap
  4. I would repeat the experiment using a 200mVpp nput signal (I think that you are using something like this) BUT using RV1 to give a gain of 10 so you get a 2Vpp signal at the input of the ADC floating over 2.5V
  5. The op-amps sockets can be dodgy. Try to measure continuity bet ween the op-amp pin and the elements of the active filter (on top side)

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