Building the Chopped OC2

[phector2004]

No, but it will fit in a 125b, just slightly larger.

Uhhh...

Are you sure??  

I just ordered a 1590B this morning...  

Am I sure about what? That it will fit in a 125b? Yes, I have my prototype one sitting right here in a 125b.

Or do you mean, am I sure it won't fit in a 1590b? The board itself will fit, but I can't guarantee it will fit with jacks and the stomp switch in a 1590b. If you measured it all out and it fits, then it fits.

The 2nd one

I guess I'll soon figure out if it does... Shouldn't be a problem for me, my ethnic stereotype involves fitting large things into tight spaces!  

This one's gonna be a doozie, though 

[pdub]

I just built this up this morning and WOW! Very cool! The tracking is very very good. I implemented the variable filter mod which I like a lot. This would be nice with an expression pedal or envelope follower.

I tested all the additional synth mod points and find those all very useful too. Looks like my build is going to have all this going on. I'll have to try the tracking mod next.

Thank you Taylor and Processaurus for a great project!

Charles 

[Taylor]

Glad you like it! Just found out that a popular boutiquer plans to make this circuit with all my mods and call it his original design. 

[MonkeyWrench32]

Here's the design I'm using for the enclosure. Why Maize Rage? I wanted a yellow pedal, plus I'm a big fan of the University of Michigan and their basketball student section is called the Maize Rage. It sounds like it should be the name of a dirt pedal, but I like it.



Here's the drilling plans. I'm getting a 1790NS from Pedal Parts Plus and having them drill and paint it.

If anyone wants an AI/SVG/etc. of either one, let me know.

I'm actually hoping my parts get here a few days after the PCB because I'm getting an Oxide from Taylor at the same time. One thing at a time!

[Renegadrian]

.

[foozertone]

I don't know if this is the right place for this but

I built a musicpcb analog octave down and it does'nt work.. Get signal on bypass but nothing with the effect on (although the LED works.

I've made no mods or subs but I wired with no battery clips and i use a powersupply

okay here's my readings:

J201                     2N3904
d-5.05                   e-4.19
s-5.06                    b-4.81
g-2.2                     c-9.4


TL074                             LM324                                  4013
1-5.43    14-.454              1-.604       14-2.08                1-.656        14-9.34
2-208      13-.44               2-.245        13-7.7                 2-.798        13-.63
3--1.92    12-0.00             3-3.77        12-2.46                3-.63        12-192
4 -9.33    11-0.00              4-9.32       11-0.00                 4-0.00       11-0.00
5-3.3        10-0.00              5-4.2        10-0.0                  5-.796       10-6.8
6-3.6       9-.45                  6-3.023      9-47.6                  6-0.00       9-0.00
7-.54        8-.45                 7-0.00        8-3.02                   7-0.00      8-14.7



1N914 diodes listed acording to the board printed side up top to bottom left to right

d1         d2             d3              d4
a=3.06    a=25.0      a=47.6       a=3.06
k=3.06     k=3.06      k=3.06       k=3.06

Ger Diode                      1n4001                             
a=.236                            a=.1
k=.224                             k=9.34


I relly would appreciate any assistance on this.  Thank you.

[Taylor]

I personally find audio probing to be an easier way to get pedals debugged than reading voltages, other than making sure the power and ground are there (which they are in your case).
http://www.diystompboxes.com/wiki/index.php?title=Debugging

Check the PDF to see where the various signals should be present (for example, the octave square wave). If your octave square wave is where it should be, we know the tracking and logic part of the circuit is working, so you'd then want to probe the audio portion.

If you don't even have clean signal coming through the pedal, with the clean volume up, then it's pretty simple: something's messed up in your audio path. Could even just be a jack. Looking at the schematic, probe TL074 pin 1 and see if you have audio. If not, your problem exists in between your input jack and there.

[Valoosj]

Taylor, do you have a soundsample of this pedal? I really like your work, you always really dig into it.

[foozertone]

I get no signal at tlo74 pin 1

is the 1uf in the schematic going into u1a located on the pcb the one under the 10 uf inthe top left corner Ibet it is cuz i screwed it up

[Taylor]

Taylor, do you have a soundsample of this pedal? I really like your work, you always really dig into it.

Thanks, no clips, but the stock version sounds just like an OC2.

I get no signal at tlo74 pin 1

is the 1uf in the schematic going into u1a located on the pcb the one under the 10 uf inthe top left corner Ibet it is cuz i screwed it up

Yes, that's the one.

[foozertone]

that's what i figured. Are there any jumpers or something I can do to salvage the board?

Thank you

Jeff

[Taylor]

How did you mess it up?

There is a little via directly below and to the left of this 1uf. The positive lead of the 1uf cap is connected to that. The negative lead of the cap is connected to pin 3 of the TL074. So if you pulled up the pads for that cap, you can solder it between those points.

[Marcvv]

Hi taylor,

I just finnished the octave down. It works. Very nice pcb, by the way. I have a good octave and I can dial in dry and octave but I also have a sort of noise that plays along the octave. I think that that should not be there.
I also have dc on the input: iIf i move the volume pot of the guitar I hear dc noise. The same  when I move the two pots of the build.
I checked all components and the direction of the caps. I also reflowed and reflowed again all the solder joints.
I replaced the lm324 as I had another one.

No change. Any suggestions?
Marc

[Taylor]

Regarding the noise playing with the octave: this is basically the square wave signal that is used to flip the phase of the signal to make the lower octave. I have noticed that sometimes this couples into the top copper pour and then into the audio path. I haven't noticed this in all of my builds and the ones by other people I've examined, but in a few. It didn't arise in any of my protos, or else I would have taken steps to avoid it in the design. The solution is to ground the top copper pour. Scrape off a tiny area of soldermask overan open area of the PCB, for example directly to the left of the GND pad, and connect this top copper pour to ground. It will erase this problem.

The DC thing: what might be happening is that, sine the input capacitor is an electro, it could be a bit leaky. You can swap out a 1uf non polar film cap in its place and my hunch is that it will disappear. LEt me know how that goes.

[Marcvv]

Hi Taylor,

Yes, the noise sounds like it is part of the square wave. I noticed the noise is in the clean signal path only. So when i turn the dry signal down it dissapears.

I scrapped some of the soldermask left of the ground pad on the side where is gnd is written. Is that correct?
When i connect that to ground nothing changes.  Any clue?

A bit embarrassing question: which 1uf is the one at the input. As there is hardly a trace visible it is hard to trace it.

Thanks, Marc

[Taylor]

The input cap is the one closest to upper left. You can actually swap both of the 1uf electros with something like .1uf nonpolars, which will still roll off below audio so it won't effect anything. These are cheaper than 1uf non polars.

You scraped off and grounded the copper pour on the top side, the side with the silk screen writing, and at the upper part of the board in between the two pots, correct? If so and that didn't solve it, that's quite strange. Do you have your input jacks grounded to the GND pads on the bottom? If so, star grounding your jacks and PCB to the power  jack ground might be the next thing to try.

[Marcvv]

Hi Taylor, thanks for responding.

I changed the input cap to a .1uf non polar and that solved the dc noise. No more crackle on the guitar volume or the pots of the chopped oc-2. So that is one problem solved

I still have the square wave bleed on the clean signal.
It seemed to be away when I changed the input cap but it is back.
I followed your suggestions ( grounding the top copper pour, star grounding the input and pcb grounds) with no effect.
I also changed the whole input and true bypass switching to be sure that that was not of any influence.

I have no clue where to look now?

Thanks, Marc

Any ideas?

[Taylor]

Not sure either - your symptoms are not anything I experienced in any of my builds. When I could hear the fuzz, it was present even if both volumes were turned all the way down, and grounding the top copper pour solved it completely.

Maybe if you can post a picture of your build somebody will notice something that might be causing it?

[Marcvv]

I will post a photo as soon as i can upload it.

In the meantime i checked everything againand again.
In the schematic there are two 10uf caps. One at the 2n3904 anf one at the 2.7k going to u1a.
In the bom list there is only 1 10uf cap and also on the silkscreen. What is the correct value and where should it go?
Do you have a pcb layout so I can trace the parts in combination with the schematic please?

Thanks, marc

[bass.toss]

Hi, I have the same problem as marc