Underminer Issues (works but sounds too weird)

[Coach_McGuirk]

I built an underminer sub-octave but it's not working properly. It does turn on and make sounds but it's... uh... much more glitchy than the videos I've seen suggests it should be. The glitching is sporadic and seems to occur regardless of the settings (glitch switch up or down and the glitch knob don't seem to reduce or increase the glitchiness very much). The 1-down and 2-down octave switch also doesn't seem to be working properly. And the blend knob doesn't pass much dry signal through; even when it's turned counterclockwise, it's not much dry signal and still a ton of weirdness mixed in. Lastly, the effect comes on strong when I pluck a string, but kind of farts out to silence a half second or second later. Honestly, it sounds pretty cool — like some sort of electronics circus act — but it's not very usable and it's definitely not what I hear when I lookup demo videos of the pedal.

I have checked to make sure that the values of the components are correct, and I've inspected the board pretty closely to make sure there aren't any obvious shorts or other issues. I'm a noob and don't really understand schematics that well, so I'm not sure what the voltages should be, but I've used my multimeter to provide the voltages for each pin below. I turned the 3 pots completely clockwise and flipped both switches up before testing. I have also tried multiple CD4046 ICs with the same result.



1: 8.78
2: 0.0009
3: Oscillates quickly between different voltages
4: 6.72
5: 0
6: 0
7: 0
8: 0
9: 0
10: 0.182 (sometimes oscillates quickly between different voltages?)
11: Climbs between 0v and 200mV every few seconds
12: 7.57 (sometimes oscillates quickly between different voltages?)
13: 0.184 (sometimes oscillates quickly between different voltages?)
14: 4.42
15: 0.26 (sometimes oscillates quickly between different voltages?)
16: 8.78

Please let me know if I should be testing the IC with the knobs and switches turned to different values.

 

[Coach_McGuirk]

Sorry, my other pics didn't attach properly. Here they are.

 

[Nic]

Where did you get your ICs ? I built that board in my early builds and also had a rough time getting it to work. That sure is a weird pedal and not much use for it, I sold mine but kind of regret it, I might do it again.

Back to your problem, that's not normal. But I also remember mine not acting all too intuitively. Still, the -2 octave was noticeable, even on the bass. And the glitch switch would go full weird.

I would start by reflowing everything.

 

[Nic]

Maybe try to sand the paint on the inside so your jacks have better ground.

 

[Nic]

I turned the 3 pots completely clockwise and flipped both switches up before testing.

Last ... if I remember correctly, start at noon on your pots and then make adjustment.

 

[Sturdag Lagernathy]

The vero "Underminer" I built sounds massive, and will never leave my board. It's a simple circuit, so I'd bet it's a soldering issue. Blend knob never cleans up completely, there's always a bit of octave, and the tone knob at center is "flat". CCW is darker, CW is brighter. Unity volume is a usable 11 o' clock..
Clean the board, reflow your solder joints(use a little Flux, keep your iron clean) and I bet you'll be in business..

 

[Coach_McGuirk]

The vero "Underminer" I built sounds massive, and will never leave my board. It's a simple circuit, so I'd bet it's a soldering issue. Blend knob never cleans up completely, there's always a bit of octave, and the tone knob at center is "flat". CCW is darker, CW is brighter. Unity volume is a usable 11 o' clock..
Clean the board, reflow your solder joints(use a little Flux, keep your iron clean) and I bet you'll be in business..

I think you might be on to something. I cleaned up the PCB and it's definitely improving. I forgot to put the IC back in the socket and it sounded quite good as a distortion/fuzz. Then I put the IC in and it's working better, although I still think there might be something wrong. Makes me think I might have a bad batch of these ICs, so I ordered some replacements and will see if that solves it. Thanks for the tips.

 

[Nic]

So, back to my first post, where did you get your IC. For my build, I ordered 2 from tayda... one of the 2 would sound really bad and the other was better.

 

[Coach_McGuirk]

So, back to my first post, where did you get your IC. For my build, I ordered 2 from tayda... one of the 2 would sound really bad and the other was better.

I ordered 3 from Tayda. They all kind of sound the same to me. I ordered some more from elsewhere and will try those.

I've gone ahead and cleaned the board as best I could and reflowed everything. It's a bit better but something is still off. I think it's the IC because the pedal sounds like a normal distortion pedal when the IC is pulled out. At this point, the board has taken a bit of beating from desoldering the transistors to try new ones. There is a bit of copper exposed on some of the traces, so I'm a bit concerned that I've reached the end of the road if the replacement ICs don't fix things. Might have to just re-order another board at some point and try again.

I will give an update once the new ICs arrive.

 

[Nic]

In the end, mine would sound like this :

I stopped ordering my ICs from Tayda, I go to Mouser mow. I know a lot of folks have good results, but I had a few times I was unsure of the IC.
I remember that the filter and blend would interact in a way I sometimes thought it was not working, like full wet and filter, but can't remember what was the exact combination.

 

[Giorfida]

In the end, mine would sound like this :

I stopped ordering my ICs from Tayda, I go to Mouser mow. I know a lot of folks have good results, but I had a few times I was unsure of the IC.
I remember that the filter and blend would interact in a way I sometimes thought it was not working, like full wet and filter, but can't remember what was the exact combination.

I am the same way. Only Stompbox parts and mouser get the majority of my transistor and Ic orders now as well.

 

[Sturdag Lagernathy]

Have you continuity checked your toggle switches?
Honestly, if your chip is coming on and affects the circuit, it's probably fine. IME, Cmos fails to silence. That said, I hope it is that easy to fix.
The circuit is basically a 2 transistor "fuzz" into a blend circuit. The fuzzed signal is fed to the PLL, then blended back into the unaffected fuzz signal. With the chip pulled out, does the filter control work fine? Does the blend knob act like a volume control?