Parentheses Fuzz: Distortion switch kills the signal.

[clipped_diode]

Click here to see the "completed" build outside of an enclosure.

I've only done three kits before sourcing parts for this PCB, so I'm still relatively new to DIY pedals. I expected some trouble from the finished pedal because throughout the build several pads popped off and the copper plate is slightly exposed in a few spots. (Ultimately, I don't think the pads caused a problem because in each instance at least one side still had a pad.)

I am using an audio signal probe to diagnose. This post is probably a little premature because I'm still trying to understand the schematic, but here's what I know right now.

1. True bypass works.
2. The effect seems to work. I get a heavy distortion (almost 8-bit velcro ) and an octave sound. I'm not sure how much this pedal is meant to clean up but even with distortion all the way off it is still heavily distorted. EDIT: Playing with a guitar it is clear that this is way more "gated" sounding than it should be. I have to strum HARD for a short spike of sound that quickly falls off. (Like velcro settings on Fuzz Factory or similar.)
3. Turning the octave knob down lowers the total output volume.
4. If I switch the octave switch, the output dies.
5. If I switch the boost switch, the output dies.

I don't have LEDs installed so it's not clear if the sound dies when I engage or disengage the switches. I assume the octave OFF kills the sound because I can hear an octave otherwise. It's not clear to me if the boost is ON or OFF however.

EDIT: Updated title to reflect current issue. It's the distortion switch that kills the signal. Octave switch does nothing. I got the boost side working after replacing a part.

 

[Chuck D. Bones]

The pedal is definitely not working the way it is supposed to work. I can see you used top-shelf parts.
Solder side looks pretty sketchy. Way too much solder on the pads. Lotta flux residue. Some of the solder joints look cold. Not enough resolution in the photos to tell if there are any shorts, but I'll wager there are some. You're gonna have to clean all of that up before we can proceed with the troubleshooting. Use a solder sucker or solder wick to remove the excess solder. Reflow any joints that are not shiny. Keep the heat to a minimum on the germanium diodes; don't reflow those solder joints. Wash & scrub the board with IPA. Do a thorough visual inspection. Repeat as necessary. When it all looks good, power it up and see if it works. If you're still having trouble, post some new pix and we'll dig into it with you.

 

[clipped_diode]

I added two photos to the bottom of the album. I used a solder sucker and removed as much solder as I could from every contact on the solder side. If the contact was flat I simply reflowed the contact. I did actually reflow the GE diodes before realizing it, but I was quick. I applied 91% isopropyl alcohol about 6 times and wiped as best as I could. Unfortunately the sharp solder joints make it difficult to really clear a lot of it with a cloth.

I powered it up and now it's not working at all except when bypassed. If I engage the boost switch even the bypassed signal dies. I'm going to try to test a few spots with the audio signal probe tomorrow.

 

[Chuck D. Bones]

Try a toothbrush for cleaning.

If engaging the boost kills the bypass, then maybe the bypass stomp switch has a problem. The boost is the last functional block in the signal chain and the bypass switch should completely disconnect it from the output jack when in bypass mode. The wiring looks correct in the photos, and as far as I can tell, the switches are oriented properly. Maybe a solder bridge between the switch & board? Or a tiny whisker of trimmed wire shorting something out?

I'd just start at the input end with the audio probe and work your way downstream 'til the signal drops out. You may not get past the bypass switch.

 

[clipped_diode]

Thanks. I started with what I believe is the boost circuit (layout and schematic). I assume the signal runs from BOOST_IN to _BOOST_OUT here.

Engaging the switch kills the audio signal to the main output. Moving to the switch, I can hear the signal leave the switch and move through R28, R29, and C22. I can hear all three legs of Q6 (leg 1 is boosted).

I can't hear anything at C23 or the boost pot. The C23 anode contact is one of the ones that popped out (see below for a "before" photo). I suppose I could wire it directly from part to part. I added a bit of solder to the contact and it hasn't helped. (Briefly, this post said the added solder fixed the issue but that was incorrect.) Bridging the connection with a spare 10u capacitor works perfectly so I think I'll just solder it in.



It's unclear to me from the layout and schematic where the signal goes next.

 

[Chuck D. Bones]

If you broke a trace or a pad, you have to jumper over the broken area and then test it for continuity with a DMM. Always jumper from pad to pad, don't try to solder to a trace. Install a jumper from C23+ to Q6-1 on the solder side. Use solid wire, like a trimmed resistor lead.

 

[clipped_diode]

Here's how it turned out with a new 10u. Negative side is in the pad and I connected the positive side to Q6-1. I did this before seeing your post or else I probably would have done it on the solder side



It works! Not only at the trim pot, but now I am getting a signal from the main output that is responsive to the boost pot setting. Switching the distortion switch on kills the signal. Switching the octave switch does nothing.

Where do I go next? I think the distortion side?

Also, can anyone tell me why it looks like the distortion LED path runs through R100 and into the IC? Is this just sending power?

 

[clipped_diode]

I've confirmed that the audio signal is moving through every component on the distortion circuit properly — at least the top part of the schematic. The remaining problems must be in the octave circuit.

 

[Chuck D. Bones]

Take a look at the other posts in this forum re: Parentheses. A few people have had problems with the octave circuit. Check the transistor voltages on the octave circuit and compare them with the results in the other posts.

 

[clipped_diode]

The (first) problem is at the IC. I hear the signal enter at pin 3 per the schematic but all other pins are silent. How can I test if the IC is functional or not?

 

[DGWVI]

Where did you source the 308?

 

[clipped_diode]

Amazon.

 

[DGWVI]

I've used a lot of DIP 308s. National, Motorola, ST... They all had an extra dimple right next to pin 1. I think you may have a fake.
If you have any other single opamps, give those a try

 

[DGWVI]

Here are some of my confirmed fakes. Also got them from Amazon

 

[clipped_diode]

Thanks, that's helpful. I just replaced it with an LM 308N I pulled from a BYOC Rat clone (that works) and it is behaving in exactly the same way. I reflowed all of the joints of the socket but I'm still not having any luck. Is there a way to test if the IC is receiving power? Based on the schematic, VCC hooks up to pin 7.

I don't have the LED installed — it looks like there is a trace running from pin 7 into R100 and into the LED above the switch. Would that do it?

EDIT: Yes, after floating an LED there I am getting a signal now (though not from the fake IC). Totally missed that detail on the schematic.

 

[clipped_diode]

Here's an update. I created a couple of wire bridges from contacts between C11 and the IC that were not holding up well on their own. Now the signal flows through — and with that, the signal now reaches the output. All switches are working and nothing kills the signal.

However, the sound of the distortion is extremely gated (as I described before), like a velcro-type fuzz. It sounds like this both at pin 6 of the IC (output) and the main output. What could be causing this kind of fuzz? Is it possible it's a power issue? I am using a standard 9v adapter. I haven't necessarily been testing each path to ground in the schematic.

Also, the octave sounds more like a ring mod. I'm not sure if this is just the nature of an analog octave and it's hard to hear clearly because of the above issue with the distortion.

 

[Nostradoomus]

What voltages are you getting on the transistor and IC of the Rat portion of the circuit? I have built a voltage sag box and run a Rat through it and it definitely goes velcro, sounds like it’s not getting enough juice!

 

[clipped_diode]

Pin 7 is reading .9 - 1 m V DC.

Not sure I can accurately measure voltages without it being in an enclosure. I don't have one drilled yet, but if it's necessary maybe that's my next step.

 

[DGWVI]

Pin 7 should be getting the full voltage from your power supply. Looking at the pics, that solder joint looks pretty dull. Hit it with some fresh solder

Also, the octave sounds more like a ring mod. I'm not sure if this is just the nature of an analog octave and it's hard to hear clearly because of the above issue with the distortion.

That's the nature of the Green Ringer circuit. Definitely a far cry from a clean octave sound. Gets flutey sounding with your neck pickup and tone rolled off

 

[Nostradoomus]

You can definitely check it out of the enclosure, have you got a testing rig for proper grounding and such?

Pin 7 should be at full voltage, what are your other pins and FET reading?