Horndog attempt

[gül]

I etched and built the Horndog. Weirdest thing is that the effect only works when I touch the side of R6 (100k) that connects to pin 3 of IC2 with my finger. 

Granted, I really am a hack when it comes to understanding this stuff... But it would be great to know what I can connect to make it work. I should point out that the effect works perfectly when I touch it in that one spot. I'm getting a nice sweep, even with a 1MB pot. Anyone have any ideas about where a connection needs to be made? I've checked my solder points around there and I have continuity all around. I'm stumped but this has been really fun to work on.

[matmosphere]

Did you put in the jumper? Under the boards image on the BOM it points out that it is there.

Hope that does it.

[gül]

The jumper is in, that's why I'm confused!

[alparent]

Last time I had this happen. It was a cold joint on an older resistor. Removed that resistor all together on put in a new one. Problem solved.

[gül]

I gave that a try, Alparent. Re-flowed solder all around one more time, too. Same weird result! I'm curious to see how yours turns out when you get to it!

When it is working (meaning when I have my finger on that junction), it suffers from the high-pitched sound that is always there in the background... Same as the TagboardFX version I built. It must just be part of the design. It's a very cool-sounding effect nonetheless. 

[blearyeyes]

Looks like the only thing you can do is to get a finger from somewhere and attach it.

[matmosphere]

Looks like the only thing you can do is to get a finger from somewhere and attach it.

Maybe arstatertotle Has a spare from his BOTY pedal with the saw blade.

[gül]

Anyone else build this yet? I etched and pop'd another board with the exact same results. All parts were tested beforehand. Just thought I would see if anyone else gave this one a go.

[PhiloB]

I have no experience with this circuit.  BUT, if your finger makes it work what about connecting that side of the resistor to ground (that's what your finger is doing)


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[gül]

Definitely tried that to no avail! I ended up building this on vero and it works fine.

[Stomptown]

So I decided to give this one a try a few weeks back and when I tested it out I was only getting clean signal.  I decided to do some research and found a thread over at GuitarFX Layouts with many builds with the similar issue.  The consensus is that a TL072 cannot reliably be used for the clock (IC2) and the solution is to use an NE5532 in its place.  I tried that and it worked perfect so I think we can call this one verified with an update to the build doc.  I should mention that many people over at GuitarFX Layouts also complained about the high pitch whine that changes pitch as the frequency control is adjusted, however I'm pretty sure that is an intentional feature of the circuit. IMO, this circuit is not well suited for guitar and would be more useful for DJs, etc. so keep that in mind.  Here is a demo I found to show you what it sounds like:

https://www.youtube.com/watch?v=3AlHpHUDOaY

[gül]

Thanks for that info. Maybe I'll pull it out of the "recycle" bin and try out your suggestions.