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TOPIC: How to Troubleshoot Pedal Pi

How to Troubleshoot Pedal Pi 2 years 7 months ago #1707

Hi Ray, I managed to disconnect the R1-facing lead of R2, but it didn't help with the drop off. R1 seems to be the correct value, measuring at around 1M. I don't know how to desolder R1 because it's so densely wedged in there... Also I don't feel like going at it more and more with the soldering iron is helping, I'm afraid to cook the board :(
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How to Troubleshoot Pedal Pi 2 years 5 months ago #1782

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Disclaimer: I am a complete noob

Hi there, I've been troubleshooting my pedal and my next step is to check software so I've tried downloading your pre-compiled Raspbian_Jessie_Lite_Pedal-Pi.zip to my Mac, however when I unzip using Unarchiver the file which I'm expecting to be .img is a Unix executable.

I downloaded balenaEtcher to try to flash this to my SD card. It gives me the option of choosing the .zip file, however when I do I receive the error "Can't find a matching file in this zip archive." Seems that the file is somehow corrupted? I tried re-downloading but got the same result.
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How to Troubleshoot Pedal Pi 2 years 5 months ago #1785

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Ok, I am downloading and doing the process to make sure that all is fine. Give me some hours!
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How to Troubleshoot Pedal Pi 2 years 5 months ago #1786

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Just download the Raspbian Jessie Lite with the BCM2835 libraries installed from mega: mega.nz/#!QzIh3Kya!evXBRlvDMUwl7lIotoBJNmtdFxaN2VjOG_h5UTZOSH0

The Raspbian_Jessie_Lite_Pedal-Pi.zip file contains a "Raspbian_Jessie_Lite_Pedal-Pi" file (without any extension). You have to manually unzip it and then add it the ".img" extension yourself.

After that, you can use the Win32DiskImager (on any similar software) to burn the .img file into your 8GB microSD card.

IMG.png
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How to Troubleshoot Pedal Pi 2 years 1 month ago #1963

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Ray, thanks for this trouble shooting guide. Has been very helpful for isolating the issue.

Actually, at first, I had the same issues as @badusername.

R1 is correct: 1 M
C1 and C2 are also correct: 100nF and 6.8nF

Voltages on R1 are 1.6V towards the test point and 0.8V on the other side.
it does not matter whether MCP6002 is connected or not.

This was solved by adding extra solder to R1. Maybe both layers of the PCB were not nicely connected.

Now, I am still having noise issues on the Zero W with wireless disabled.
This makes, for instance, the fuzz effect completely unusable. It just screams all the time.
Also, I have the impression that the output levels towards my amp are a bit high.

Do you have a suggestion for how I can fix this?
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How to Troubleshoot Pedal Pi 2 years 1 month ago #1965

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Found a solution. I suffered from two issues. A defective MCP3202 that created a lot of noise. In addition, the output stage filter involving C6+C7+C8 does not appear to suffice. The cutoff frequency of 5kHz did not filter all PWM noise. Replacing these caps with 10nF each (cutoff frequency around 3.5 kHz did the trick. Works very well now.
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How to Troubleshoot Pedal Pi 2 years 1 month ago #1967

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hi ppi,
This was solved by adding extra solder to R1. Maybe both layers of the PCB were not nicely connected.
Yes, most of the times that "cold joints" are the source of most of the problems.
Now, I am still having noise issues on the Zero W with wireless disabled.
This makes, for instance, the fuzz effect completely unusable. It just screams all the time.
Also, I have the impression that the output levels towards my amp are a bit high.

The pedal is not always totally quiet, there is always some background hiss, but the signal should be much louder than the hiss.
The fuzz sometimes depends on the signal level of your guitar, sometimes adjusting the input trimmer helps to get more signal (or less in case you are overloading the circuit.)
Found a solution. I suffered from two issues. A defective MCP3202 that created a lot of noise. In addition, the output stage filter involving C6+C7+C8 does not appear to suffice. The cutoff frequency of 5kHz did not filter all PWM noise. Replacing these caps with 10nF each (cutoff frequency around 3.5 kHz did the trick. Works very well now.
The MCP3202 that I get are from USA Mouser, usually the best source of components, I am sorry if yours was defective.

When we designed the output filter (schematic here : www.electrosmash.com/images/tech/pedal-p...pi_block_diagram.jpg) we did that sallen and key filter to cut frequencies below 4.9KHz, you can use this calculator check it: sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm

Using 10nF caps (instead of the standard 6.8nF) lowers the fc to 3.3KHz, is not a bad option and if it helps to drasticly reduce the noise go for it. Iam probably going to link this from the troubleshooting guide.

That filter fc is a trade between clean sound and "more real" sound. It is difficult to set it beacuase everybodys setup is different.

Thanks for yout input!!
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