Pork Barrel issue. Wonky oscillation, like whales mating lol [RESOLVED]

[Twilt]

Hi all.  First Madbean build, first issue, first post.

The pedal works perse.  I have guitar signal when bypassed, status LED lights when engaged, rate indicator LED responds to rate adjustments.
  However, when pedal is engaged, no guitar signal passes, only a weird midrange oscillation.  Also, the rate indicator LED remains lit even when in bypass.

Voltages:

IC 1
1=4.5      8=9.19
2=4.5      7=4.5
3=4.5      6=4.5
4=0         5=4.5

IC 2
1=0          8=3.74
2=4.26     7=3.74
3=3.72     6=4.24
4=8.2       5=8.78

IC 3
1=8.78      8=8.2
2=4.24      7=2.9
3=0           6=8.4
4=4.26       5=.32

IC 4
1=.14~.79   8=9.19
2=4.3~4.8   7=2.8~6.8
3=1.6~6.7   6=4.78
4=0             5=4.4~4.7

Q1             
1E=3.3         
2B=3.78       
3C=9.19   

Q2
1E=3.72
2B=4.29
3C=9.19

Q3
1E=3.45
2B=3.97
3C=9.19

Q4
1E=3.4~3.8
2B=4.0~4.3
3C=8.78

Q5
1E=0
2B=4.2~4.3
3C=7.3

A few of the reading don't match up with the ones in the build doc's.  Possible a few of the build doc readings are backwards? (i.e. Q1 & IC 2)

Any ideas on where to go from here?

Thanks.
~Troy

[thomasha]

Which build doc are you using? I have the 2019 one, and voltages seem correct for the MN3007.
Voltages on IC2 depend on the type of BBD that you used, though.
Unfortunately, the image is too dark to identify your IC2. Voltages suggest a **3207. Are you using the correct clock (3102)?

Have you tried checking the signal path with an audio probe?

[Twilt]

Thanks for chiming in thomasha.

Yeah, I used the 2019 build docs.
BBD is MN3207 Clock is MN3102.

I have not audio probed it yet.  I have one, just haven't gotten to it yet.

[Twilt]

Just sat down with the audio probe.
When pedal is engaged, i can hear a VERY faint signal underneath the MUCH louder "buzzy chorus effect".  It does not change from R1 to the output.  Checked a couple of points in between with the same result.

Im wondering if it's the switch?  Seems a bad switch would either work or not.
This seems more like a bad component of some sort.

But, that's why i'm here.  Im experienced in building these, but dont know much other than how to solder and follow the build docs lol.

~Troy

[thomasha]

Well, that might be a cold solder joint at some ground in the circuit. Every time I have buzz it's either a bad cable or wiring problem.
Your wiring looks exactly like the one in the PDF, but It could present some lose or cold joints.

How are you using the audio probe? Are grounds connected? There should be no noise at R1.
Noise at R1 means noise at the input jack. Any weird noise caused by the circuit should not be present at the input, unless there is a problem with grounding.

Does it work when bypassed? Or is the noise bleeding through even when bypassed?
Can you check continuity between some ground points and some components? For example, one side of R1 should be grounded.

[Twilt]

Maybe "buzz" was the wrong word to use. Loud Distorted chorus is more what I'm hearing over top of the faint signal when engaged.

In bypass everything is crystal clear.

Working through the schematic, all grounds have continuity.

Including pin 4 of TL062, pin 3 of 3102, pin 1 of 3307 and pin 4 of 4558.

[thomasha]

Ok, that changes things a bit.

Distortion can be a result of wrong bias somewhere. Probably at the input of the BBD.

My suggestion would be analysing parts of the circuit:
First, remove the mix resistors (If the MN3207 is socketed removing it will break the signal chain there, and no desoldering is necessary).

Let's hear how it sounds without chorus at all (just the clean sound). If there is something wrong with an OpAmp it should be noticiable.

Second, there should be no distortion (when using the audio probe) until you get to the input of the BBD. Chorus do not have feedback, so there should be nothing returning to the begining of the signal chain.

Third would be to remove everything associated with the BBD (clock, BBD, LFO(TL062)) and see if the clean signal works now.

That should give an idea where the Problem is.

[Twilt]

Thanks thomasha.

Yep, all the IC's are socketed.
I will walk though those steps this evening and report back.  Thanks again!

~Troy

[Twilt]

Ok.   So, with the BBD removed and all other chips intact, all I get is nice clean signal, whether engaged or in bypass.  Signal is a little louder in bypass though, which I suspect is normal.

With all chips removed, it is still a nice clean signal.  Again, just louder in bypass.


FYI, all the distortion/buzz I was getting while using my audio probe was because I had the gain maxed out on my interface   oops!
That has since been adjusted and no more distortion.
So without all the interference from too much gain and with all the chips in place, the oscillation sounds more like a cop car siren than whales mating 

[thomasha]

Do you think it changes with the speed knob, and could be associated with the LFO?
Or is it more like delay feedback oscillation?

The first case would be leaking LFO. But that would be weird, since it should be there when you remove the BBD.

The second case would be a short somewhere in the wet line to the input or a specific position of the input.
What is weird, is that it should be really fast. Maybe the LFO changes that.

My next suggestion would be AC grounding some places through a cap (anything between 100n to 100 uF, one leg to the signal path, the other to ground). Start from the mixer stage and go towards the BBD. It will short the wet signal and at some point there should be no noise left.

If you are lucky, it is in the region where the signal is shorted to the input. Otherwise, you just cut to much of the signal.

[Twilt]

With the BBD intact, it definitely changes speed.  Depth also works bc it does intensify the signal.

The rate LED doesnt impact the audio signal, does it?  I ask bc throughout my trouble shooting, the LED is not mounted.
Also, i removed the Mix pot to take thst out of the equation.

[Twilt]

When I get home this evening, i am going to replace the footswitch.  I have suspected it all along because it's of the cheap variety and I've run into problems with them before....being way too sensitive to heat.
I will report back tonight.

[Twilt]

Well...turned out to be the damned switch 
Just soldered in a fresh one...and BLAMO!  WE HAVE CHORUS!
Pork Barrel sounds AWESOME!

This is the 2nd or 3rd bad switch from this batch.  The rest of them are now in the trash!

Thanks for your patience and all your help, thomasha!
Much appreciated!

~Troy