Kaleidoscope troubleshooting

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markelm

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Hi everyone! First post here, so I'll introduce myself :) I'm based in Stockholm, and I recently started building some eurorack modules. I have also built one fuzz pedal so far, this Kaleidoscope being my second DIY pedal.

I finished the build yesterday, but I don't get any wet signal from the pedal. Volume and Mix pots work fine, but as I turn the Mix pot right, the sound fades (as if the wet sound was not there). I tested the 3.3V pins in the ICs and they are fine. LED works fine, bypass works fine.

I might be missing something, but I am finding it a bit hard to debug since the schematics in the documentation don't match the PCB quite right, since the pythagoras board seems slightly different. I attach a picture, any help would be much appreciated!

Thanks in advance!
/markel 373
 
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you should make an audio probe (basically an audio cable to your speaker that is grounded to the pcb and has a capacitor on the signal wire -- use google to find some simple directions to make one).

using the probe and putting a signal into the powered-on pcb, test the fv-1 chip on pins 1 and 2 to see if your audio input is present. after you make sure audio is going into the fv-1 chip, check to see if you have audio coming out of pin 28. if you have audio there, you use the circuit diagram to check the other components to see where the signal is stopping before it reaches the mix pot.
 
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zgrav said:
you should make an audio probe (basically an audio cable to your speaker that is grounded to the pcb and has a capacitor on the signal wire -- use google to find some simple directions to make one).

using the probe and putting a signal into the powered-on pcb, test the fv-1 chip on pins 1 and 2 to see if your audio input is present. after you make sure audio is going into the fv-1 chip, check to see if you have audio coming out of pin 28. if you have audio there, you use the circuit diagram to check the other components to see where the signal is stopping before it reaches the mix pot.
Click to expand...

Thanks zgrav! This seems to be an incredibly useful tool, will look into making one!
 
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Alright, I just built the audio probe (super nice tool, thanks for the tip zgrav!) and I can hear the guitar on pins 1 and 2 of the FV-1, but interestingly nothing comes out from pin 28. It's funny that the grounding noise still stops when I touch pin 28, just like when I touch a pin with the guitar signal, but nothing comes out.

I retouched the whole IC, measured all the 3.3V pins again, all checks out, but still no wet sound :( I also tested continuity to the crystal, and it seems fine. Any other ideas on what I could try?

EDIT: I meant pin 28, not 26!
 
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in addition to having 3.3v on pins 6 and 8, check your circuit diagram in the build doc and make sure you have ground on the fv-1 on pins 7, 11 and 12. also make sure that your audio output on pin 28 is not grounded.

if all of that checks out, you might have a bad fv-1 chip. where did you get it? I had one bad fv-1 chip I ordered from a low-cost supplier that was a disappointment to diagnose and remove from the pcb.
 
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Ground on pins 7, 11 and 12: check
No shorts to ground on pin 28: check

Thanks for the help zgrav, it does look like the chip is bad. I got it from das musikding as a kit fromgermany, it's been a great supplier in the past, I guess a bad chip can happen to anyone. Will contact Klaus.
 
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markelm said:
I do!! Thank you so much!! Does this mean R5 could be the wrong value?

(also, I get some sort of chorus/tremolo, didn't know this was what it did)
Click to expand...

What you're hearing isn't the Kaleidoscope effect. Grounding that point forces the FV1 to run one of its internal programs instead of the algorithm on the EEPROM.

Make sure the EEPROM is installed correctly and double check the solder connections on the EEPROM and pins 14 and 15 of the FV1.

If none of this makes any difference we'll have to get you a replacement EEPROM.
 
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Robert said:
What you're hearing isn't the Kaleidoscope effect. Grounding that point forces the FV1 to run one of its internal programs instead of the algorithm on the EEPROM.

Make sure the EEPROM is installed correctly and double check the solder connections on the EEPROM and pins 14 and 15 of the FV1.

If none of this makes any difference we'll have to get you a replacement EEPROM.
Click to expand...

Ah right, that makes sense!

Pins 5 and 6 on the EEPROM beep with pins 15 and 14 respectively on the FV-1, and non of them seem shorted to ground. All the other pins on the EEPROM are grounded, except for the 3.3V one. Still no wet sound though...
 
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