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TOPIC: How to Troubleshoot pedalSHIELD MEGA

How to Troubleshoot pedalSHIELD MEGA 10 months 1 week ago #1634

  • Ray
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I am using two 2500 mah lithium cells that produce 8.25 volts and there are no noise problems at all.
Great to hear that.
I see the VUE meter in some pictures, but not in any of the published code. Does the Mega not have enough power to handle it?
Have a look at the best topics:
www.electrosmash.com/forum/pedalshield-m...forum-topics?lang=en
Some of them are related to the VU meter
(I have tried myself to move the gauge with the guitar level but I never had the patience to finish the code)
I like the Mega shield, it meets my expectations.
Thanks! :)
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How to Troubleshoot pedalSHIELD MEGA 7 months 3 days ago #1760

  • jcarc10
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i just built my pedal board and uploaded the multi effects to it. the delay works fine but all thw other effects are super quiet and get a crappy distortion. i tried to test it just using the distortion code and got the same result. Super quiet effect and for some reason a clean on top of it. could i have blown something? using a 9 v wall adapter. And all my buttons work.


thanks
Last Edit: 7 months 3 days ago by jcarc10.
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How to Troubleshoot pedalSHIELD MEGA 7 months 2 days ago #1761

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With the volume the most usual problem is adjusting the RV1 potentiometer, did you try that?
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How to Troubleshoot pedalSHIELD MEGA 2 months 4 weeks ago #1916

  • Tigibus
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I just receive my pedalShield MEGA from you and built it.
I have a very similar problem than jcarc10 : I tried Distorsion sketch and nothing happens, just very very faint effect with a clean sound. If I change the distorsion value, around 3000 the sound drop to the silence.
I tried the multi-effect program and only the delay seems to work BUT when I change value nothing change. It's more like a reverb... Other effects do not work or just make some strange noise : bit crusher makes a loud noise at low value and nothing after value 4-5 for example.
So, to fix it I tried :
- double check all components
- re soldier all the component adding some lead to each point
- Tried all the sketches suggested to fix : triangle wave signal for output stage, clean signal for input, monitoring... All work fine (ADC value ~4800 on monitoring) !
- I check all the V values on the board and all looks fine : 2.5V, 1.7V, 5V on the chip and all is ok...
- Tried different RV1 values.

And nothing works properly, the OLED works fine.
Oh and last point : I tried on two different genuine ArduinoMega board and nothing changes. I tried USB power and a power supply 9V.

Could you please help me ?
Thank you
Last Edit: 2 months 4 weeks ago by Tigibus.
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1918

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Hi Tigibus, seems that you already checked a lot of stuff, but Im sure that we can go further.
It's kind of normal that the distortion effect may sound not great in your system. The fuzz and the bitcrusher are usually easier to adapt to any guitar but I found that from one guitar to another, the distortion code as a small threshold when it sounds good.
Maybe changing the distortion_threshold may help you:
int input, distortion_threshold=6000; //initial value adjusted by try and error.

However is definitely something happening in your pedal, so are you able to have the clean code working?
www.electrosmash.com/forum/pedalshield-m...5-clean-guitar-pedal

Usually, the voltages are the first thing to check, then I check the output stage and if not sometimes I have a fishy soldering point on the op amp, sometimes the socket makes a bad contact, can you check continuity between the actual pins on the op amp and the bottom of the board?
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1919

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Hi - I seem to be having issues with noise aswell. I have gone through all the suggested methods to try and find the problem.
I have switched C1 and C11 with MTK capacitors of the same value, but that should not be a problem?
I am also using a 12V power supply.

I can only seem to get 1.4V on pin 5 on the Opamp, i dont know what might cause that. The other pins read about 2.8V except for the ground and VCC pins.
Also the 2.5V control point is only 2.39V but i don't know if that i too far off.
Last Edit: 2 months 3 weeks ago by christian.
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1920

  • Tigibus
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Hy Ray thanks for your help.
I just check the Clean code and it works... BUT only have sound when RV1 is full left. Before it's a kind of very very faint clean signal with noise even when used with power supply. The sound dramaticaly drops until it's not at full left position. It looks like not enough signal went off the opamp and 500K is too much for leveling the faint signal.
Concerning the fuzz, honestly the effect through the pedal doesn't look like fuzz when I try the code. It's a kind of melting crush/distorded/saturated noise not a silky fuzz as I know with analog pedals.
I tried on 3 different guitars : single coil Telecaster, Humbucker on PRS with different combinations and the sound does not change, nothing good.
If I see your video presenting the pedalShield, the sound is clean, very well defined and the effects are what we are supposed to have.
I check this morning before posting here to re-melt lot of contacts on the board adding more lead but at this point, some lead begins to pass through the board and is visible on the top side making some "bubble"... I stop it avoiding to make shortcuts, I'm pretty sure it's not a cold junction, I personnaly built dozen of analog pedals and I can see if the welding is good.
For the opamp : The V at each pin are :
1 : 2.83V 8 : 4.93V
2 : 2.83V 7 : 2.83V
3 : 2.83V 6 : 2.87V
4 : 0V 5 : 1.4 V

Something is wrong with PIN5 that should be 2.6V... What can it be ? What are the R2, R3, C2 V values ? How can you have 2.6V on PIN 5 when this is connected to guitar input and only 2.5V on R2 ???

Concerning the other Voltage points, all are in the value (4.96 FOR 5v, 2.38 FOR 2.5v, CONN5 at 3.7V with RV1 at middle position.).
What is strange is this is EXACTLY the same problem than the other guy on the "TOPIC: Incorrect voltages on op amp" and few people who wrote on the forum last times experience all the same symptoms : Christian, LdCmd and me now...!!! A deffect batch of board/components ???
Please find a solution for us, personnaly I lost too many time on it trying to debug and looks like it's a common problem for all the recent sales from you.
Thanks.
Last Edit: 2 months 3 weeks ago by Tigibus.
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1921

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I just check the Clean code and it works... BUT only have sound when RV1 is full left. Before it's a kind of very very faint clean signal with noise even when used with power supply. The sound dramatically drops until it's not at full left position. It looks like not enough signal went off the opamp and 500K is too much for leveling the faint signal.
The RV1 resistor timer acts in an "exponential mode" (it's not perfect but makes the circuit much simpler). That means that the last part of the swipe contains almost all the action, so it is normal to feel the change at the end of the pot turn.

Regarding pin 5:

Untitled_2019-08-24.png


you would also need: www.electrosmash.com/images/tech/pedalsh...-MEGA-start_pcbs.jpg

From the voltage divider, it is normal to lose some level over R2 and R3. Could you compare your voltages with the ones I am measuring?
What are the R2, R3, C2 V values ?
you can see them in the image above

Please check those voltages and let me know, seems that your pedal is almost working. Looks that maybe the guitar is not reaching the op-amp properly. It would be great if you could measure the guitar signal at pin5 but I understand that not everybody has access to an oscilloscope.

It would be interesting if you can send me a photo of your build especially of the op-amp area.
Last Edit: 2 months 3 weeks ago by Ray.
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1922

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Hi - I seem to be having issues with noise aswell. I have gone through all the suggested methods to try and find the problem.
I have switched C1 and C11 with MTK capacitors of the same value, but that should not be a problem?
I am also using a 12V power supply.

I can only seem to get 1.4V on pin 5 on the Opamp, i dont know what might cause that. The other pins read about 2.8V except for the ground and VCC pins.
Also the 2.5V control point is only 2.39V but i don't know if that i too far off.

It is normal to have some level of hiss on the pedal, the Arduino platform was never designed to be used as a guitar pedal but this "hack" gives in general a good noise to signal ratio and the gutiar level should be much higer than the his level. But if you mute your guitar dont expect the board to be 100% quiet. We tried many methods to fix that and the current build is the best we can do.

Could you check your 1.4V voltage with the diagram above and let me know your levels?
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How to Troubleshoot pedalSHIELD MEGA 2 months 3 weeks ago #1923

  • Tigibus
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Thanks. But all the Voltages mentioned before does not fit with yours. After R2 I found 1.40V like on PIN 5 but 2.4V at 2.5V area before R2.
I used a lot of time the image from your link to double check all the tracks on the PCB and where are supposed to be the different components and it's exactly like mine. I can make a Copy/Paste for your photo and my board.
Last Edit: 2 months 3 weeks ago by Tigibus.
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