Pork Barrel help, please. No Chorus effect, 2nd attempt, tearing my hair out.

[heathxx]

Pork Barrel
I don't see a version, but I just got it a couple of days ago.

Problem:
No Chorus effect, just dry signal through circuit.

Steps taken to resolve
Double checked all parts and orientation, used a capacitor tester on each cap before using, replaced MN3007 and MN3101 with a known good set that were in another build (vero CE-2 pedal) and working perfectly, checked for solder bridges and cold joints, took voltage measurements, tried fresh batteries, tested signal going into MN3007 and coming out, tried sacrificing a chicken to the voodoo lord Goopaloopa (didn't work for the circuit, but it did get rid of a wart and might have cursed an irritating co-worker).

No parts substitutions (unless you count using tantalum caps instead of electrolytic), all per the build guide using MN3007 and MN3101.

Details:

PLEASE HELP...  I'm a fairly experienced pedal builder.  So far, just from Mad Bean, I've successfully built the Zero Point SDX, Cavedweller, Smoothie, Bloviator II, Sharkfin, Stage Fright, Current Lover, Harbinger One, and Collosalus, but I have tried TWICE to build a Pork Barrel and I get the same problem.  I get a good strong non-effected signal through the circuit and that's it.  The Depth and Rate don't seem  to do anything.  I cannot figure out what I seem to have done wrong both times.

The circuit is not boxed and I do not have it routed through a stomp switch. 

R1 is empty.  No resistor and no link, per the build instructions for using the MN3007 chip.

D4 is empty.  No resistor and no link, per the build instructions for using the MN3007 chip.

I get a signal going in Pin3 of the MN3007 but nothing coming out of Pins 7 or 8 (it might just be my ears playing tricks on me or maybe the slow creeping insanity of this project going tango uniform twice... but I think just *maybe* I hear a barely audible effect when I audio probe Pin 7 or 8 ).

I did the horizontal links per the instructions for using an MN3007.

I've tried the entire scope of the the trim pot and still no effect.

Here are my voltage measurements.  This is with the trim pot in the middle, Rate turned down to catch the fluctuating voltages and Depth maxed to get as full a scope of what it's doing as possible... that might be complete crap but it sounded reasonable to me.  So, anyway:

tl062
1: 0.74 - 8.8
2: 4.5 - 4.9
3: 2.5 - 7
4: 0
5: 4.5 - 4.9
6: 2.74
7: 2.5 - 6.9
8: 9.5

JRC4558D
1: 4.8
2: 4.8
3: 4.8
4: 0
5: 4.8
6: 4.8
7: 4.8
8: 9.5

MN3101
1: 9.25 - 9.45
2: 4.8 - 5.2
3: 0
4: 4.8 - 5.2
5: 0.35 - 0.82
6: 7.5 - 8.3
7: 3.0 - 3.7
8: 0.62

MN3007
1: 9.4
2: 4.8 - 5.4
3: 4.02
4: 0.62
5: 8.7 - 8.9
6: 4.8 - 5.3
7: 8.7 - 8.9
8: 8.7 - 8.9


I AM using the "Two-for-one" LFO indicator/Depth mod with a 22k resistor.  The LED pulses like it should and changes tempo with the rate knob.  So I lied above, the Rate knob does do something. 

I ended up tossing my first attempt at this in the trash.  Just now ordered another to try it again.  I need forum mojo.  Help me O-madbean-wan Kenobi, you're my only hope. 

Oh, yeah, pictures:

[jkokura]

Great job on the trouble shooting so far, and good for you for keeping your humor. Stick with it, I don't see why you can't get this one working (don't throw it out).

I think you might need to clean up some of your soldering work a bit there. I see a couple places where I don't think the joint is as good as it could be, and I think you may have the potential for some solderbridges. Obvious places to check would be anything 'after' the MN3007 in the schematic, so start at pins 7/8 and move on to R20 and C13 and so on.

I don't see much wrong with your voltages. Obviously your clock is working, so that's a good start.

Lastly, I would double check your whole section following the MN3007 before getting mixed back in with you clean signal. There's a bit resistor and cap network there for filtering, with a transistor gain stage for amplifying (Q3) that you should be getting signal through. If your signal is hitting pin 3, and the LFO seems to be working (rate LED flashing), then it only stands to reason that you have a part error, bad joint, or perhaps a backwards part (not likely because there are few polarized parts there) in the section after the MN3007 and before the output buffer gain stage.

Hope that helps.

Jacob

[heathxx]

I appreciate the feedback and I plan on putting it to use when I get home from work.  Thank you!

[Scruffie]

I have to disagree with Jacob, your voltages don't look right and it's not definite your clock is working.

3007 Pin 5 should be ground, not voltage.

Pins 2 & 6 (clock inputs) shouldn't be varying... but we'll put that down to your multimeter not settling for now.

The outputs on it seem very high for the bias voltage, but that's probably because it's not getting ground.

Yes your LFO is working, the VCO may not be, come to that after you find out why the 3007 has voltage on ground (bad solder joint or a solder hair).

Oh and just to clarify, Q3 isn't a gain stage but a low pass filter stage

[jkokura]

I have to disagree with Jacob, your voltages don't look right and it's not definite your clock is working.

Listen to Scruffie, not me. I was really just looking at your OpAmp voltages, and that the clock has a swing on pin 1. He's correct.

Jacob

[Bret608]

I am almost positive I see a solder bridge from one of the jumper pads under the MN3007 to one of the pin pads of the MN3007 itself. That would back up what Jacob pointed out, and could account for the voltage issues Scruffie noted. It could just be some flux picking up camera glare, so hopefully others can double-check my eyes here! If I'm right, it could be as easy as gently scraping out extra solder between the two pads (depends how thick the bridge is).

Hang in there, this build is worth it! I had some grounding/noise issues when I first tried to box mine, and even messed up a pad pretty good when I was populating the board. It was very rewarding when it all came together.

[heathxx]

I think I might have spotted the problem.  I *think* (I'll need to look at it closer when I get my hands on it) that pin 5 of MN3007 connects to one of the horizontal links... initially I had a drop of solder glob between the two (which I realize now wouldn't have mattered since they are connected in the pcb circuit) and after trying everything else to remove the potential solder bridge, I scraped it clean (you can see this in the "solder-side" picture) which I think might have broken the connection between the two points completely... again, I'm at work right now, so I might be going down the wrong track, but if that link goes to ground, it would definitely explain this.

[heathxx]

Bret, yep I think we're looking at the same thing, except I think it's actually a solder crevasse that needs a bridge now

[Bret608]

That is indeed where I was looking! 

You can use your DMM to check for continuity between those two points. If there is none but should be, it would be easy to use a bit of spare component lead and solder it to the two points. Also easy to undo if it doesn't work. Best of luck!

[heathxx]

That was it   When I slopped solder between those two points and couldn't get it all out from between them, I caused myself a serious pain in the butt by scraping at it.  A little glob of solder and it's working nicely.

The agony... the ecstasy... the Porkbarrel.

Thanks, guys, I really appreciate the help.

[Scruffie]

Next time... buy a de-solder pump  (spring loaded, not the bulb things).

Glad you got it working man! It may be worth adding a little wire off cut to hold the bridge together a bit more securely, probably nothing but a bit of structural integrity never hurt anyone.

And when do I get my BBD Basher title 

[Gledison]

The agony... the ecstasy... the Porkbarrel.

Hahha! Nice sentence! Enjoy the Pork!
Cheers

[Bret608]

Glad to hear you got it working too! Can't wait to see a build report.

[heathxx]

Oh, I have something special in store for this.  It might be extraordinary... it might end up a shameful mess... either way it'll be fun. 

Watch this space for the Cthulhu Chorus.