Leprechaun/EQD Rainbow Machine problem

ch ra

New member
Hello, I've been building pedals for a few years now but I am new to this forum. I built up the Leprechaun and ran it through my testing rig. Right now, I get only clean sound when the circuit is hooked up. Since the schematic isn't up yet, I'm stumped about how to troubleshoot this but I'm wondering if any of you have any ideas. As you'll see from the photo below, I ran out of 1uF MLCCs and used a few box capacitors as substitutions, but I can't imagine that would be a problem. Also, I've not hooked up the switches or expression jack (though I added a jumper for the jack as seen below), I am just running in and out directly and do not have the magic switch hooked up--could that be it? I don't believe the pot connections are the problem--when the photo was taken I did light connections so that I could re-adjust them when I box the pedal, but since them I've made all of the joints for the pots clean and solid.

I'd appreciate any advice or info (e.g., voltages) that you might be able to provide. Thanks!



67950795_411233962820009_7688046139068645376_n.jpg
 
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zgrav

Active member
How odd. I don't see an EEPROM on this board. I wonder how that came to be, since it seems really unlikely that this pedal uses the built in programs on the FV-1.

Here is are some things you can check. When you have a project using an FV-1 chip, I would start by looking at the schematics for a couple of other FV-1 projects like the Arachnid to get a feel for how the audio signal is sent to the FV-1 on those boards. Then you can use an audio probe to see if the audio signal is getting into the FV-1 on pin 1. If no sound is coming in, you can search for a bad connection through the parts that likely go there. If you have an audio signal going into pin 1 (and probably pin 2), see if you have sound coming out of the chip on pins 27 and 28.

If you have sound going into the FV-1 but not coming out of it, I would usually guess there was a problem with the EEPROM code but it doesn't look like this pedal has an EEPROM. Maybe it is using an internal set of code on the FV-1 and there should be sound coming out of the chip if sound is going in. If no sound is coming from that chip, you could check to see if the FV-1 is getting power and ground on the right pins based on the other schematics. Not sure what to do after that if you are not getting any output from those last two pins on the FV-1.

If you have some processed signal coming out of the FV-1, find out why it is not making it to the mixer pot.
 

ch ra

New member
Thank you this is really helpful. Does anyone know which pot is the mixer? Is it first order and second order for the primary and secondary pitch shifts?

Your post has me thinking that maybe the problem is around the pitch shift pot--if the pot was not shifting pitch then the output would sound clean right? Then again if that were the problem it seems like the other pots would have some effect.

One more thing that might help--I'm using a 9V battery in my testing rig. Is it possible that is not providing enough juice to power the effect? seems like the FV-1 doesn't demand much power, but I don't know.
 

zgrav

Active member
You should use an audio probe to see if any audio signal is going into the FV-1 and coming out of the FV-1. That will probably help you make better guesses about what it going on. Without seeing the schematic, it seems likely that the dry signal you are hearing is going through a separate set of components on the PCB and you might not be hearing anything coming from the FV-1. When you look at the other schematics you will see that there are usually 3 pots that control functions inside the FV-1. If the signal you are hearing was going through the FV-1, I would think some of the pot controls on your PCB would be working.

I probably would go ahead and wire in the "magic switch" just in case it is a factor and you cannot rule it out without the schematic. On the build documents it is referred to as "regeneration" so it likely ties in to the FV-1 controls using unicorn dust and leprechaun whiskers. : ^ )
 

ch ra

New member
EDITED: Looking at the Arachnid schematic, looks like that be pins 1-2 for input and 28 for output right?
 
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zgrav

Active member
at least check pins 1 (IN) and 28 (OUT). pins 2 and 27 are often tied to the one beside them, since these pedals do not use the stereo channels as separate inputs and outputs. (there may be some projects coming that will do that, but none yet)
 

ch ra

New member
Nothing at the Fv-1 input or output pins and also nothing from the second TL072 (IC3). The first TL072 (IC1) is fine. I've checked and both of those ICs should be ok though (swapping does not make a difference).
 

zgrav

Active member
That is pretty useful information when you think about it. Find the output pin from your working TL072 and use a wire to connect it to pin 28 on the FV-1 to see if you get sound at the output on your board. If you do, try moving the wire from pin 28 to pin 1 to see if you can get sound going through the FV-1 and then through the rest of the board. If you do, then the problem is in the audio path between the working TL072 and the input for the FV-1. Check parts on the board closely for bad solder connections or shorted pads.
 

PedalPCB

Administrator
Staff member
How odd. I don't see an EEPROM on this board. I wonder how that came to be, since it seems really unlikely that this pedal uses the built in programs on the FV-1.
It does use one of the internal programs. ;)
 

ch ra

New member
I think I fixed the problem thanks to pedalPCB support. Turns out the culprit was R24. My component value was way off because...late night soldering in poor lighting conditions. :sleep:

It's working now, though I need to get that magic switch set up to really test it out. Anyone happen to have a photoshop or illustrator drill template?
 

ch ra

New member
Cool, I saw those and it's great that you included them. I like to work in .AI vector format or with photoshop files because it makes it easier to set up the artwork around the drill spots. Not a big problem to get those together I just thought I'd see if folks have already done it.
 

thedwest

Member
Cool, I saw those and it's great that you included them. I like to work in .AI vector format or with photoshop files because it makes it easier to set up the artwork around the drill spots. Not a big problem to get those together I just thought I'd see if folks have already done it.
I've been able to save the PDF from the build docs and then import into photoshop and it comes in true to size. Then I just erase all the words and extra lines and design on layers underneath the drill template.
 

ch ra

New member
Finally boxed it up and looks like it is working, though I admit I'm not 100% sure it is working properly. What exactly does each pot control?
 

Chuck D. Bones

Well-known member
Same thing as the EQD Rainbow Machine, I would think. Lots of info on the EQD website, including demos. PedalPCB designs are a faithful recreation of the original pedal. The Leprechaun should behave like a Rainbow Machine. The only place where I've seen PedalPCB deviate from the original is with soft switching and touch switching. Looks to be the case here with the "Magic" switch. You can use a latching stompswitch or a momentary stompswitch for Magic, but not both.
 

ch ra

New member
I figured this is the case but the names are different. Are these the equivalents:
EQD PPCB
Primary . First Order
Secondary Second Order
Pitch . Spectrum(?)
Magic . Regeneration (?)
Tone . Color(?)
Tracking . Dispersion(?)
 

p_wats

Active member
I figured this is the case but the names are different. Are these the equivalents:
EQD PPCB
Primary . First Order
Secondary Second Order
Pitch . Spectrum(?)
Magic . Regeneration (?)
Tone . Color(?)
Tracking . Dispersion(?)
That sounds right based on my build. The knobs of the Leprechaun are in the same positions as the Rainbow Machine.
 

Robusto

New member
Will there be a schematic for this soon? Just finished it and of course it doesn't work, which I always expect on the first try.
 

Chuck D. Bones

Well-known member
You expect it to not work? :(

Visual inspection: Solder joints, debris, part values, orientation. Take your time, lotta magnification and good light. Most problems are found this way and it's usually the quickest.
 
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