Another Cindi Dilemma

[frets]

Hi Guys,

I have been obsessed with building pedals before I went on vacation and now after. I’m had an interesting effect occur that I was hoping someone could explain. I breadboarded the pedals; then, made pcb boards which I am proficient at doing. The problem is many of the pedals do not work. Now I know you’re going to tell me that I’ve probably designed them wrong but I have checked the diagrams against my boards and they correspond 100%.

While testing, I noticed that a dead pedal comes to life if the hots on the input and output jacks touch. What is that about? The Volume works but controls like Gain and Tone seem not to work.

Secondly, I have done continuity testing with a meter and the dead boards check out in terms of voltage and signal.

I am doing something fundamentally wrong repeatedly in my designs and wondered if you guys had any thoughts.

I have gone back over the pedals boards and checked each solder point retouching them with the iron to ensure adhesion (for a better term).

I know this is a quandary difficult to answer in a forum. But again, when the input and outputs touch, the dead pedals come to life.

I have poured over the diagrams and even redesigned each board and had them remade, yet the problem persists.

Any thoughts?😸😸😸

[sumgai]

Dec 29, 2022 17:34:32 GMT -5 frets said:

when the input and outputs touch, the dead pedals come to life.

Errrrr.... no, they didn't come back to life.

All you did was short the connection between input and output, which is the same thing as activating the bypass switch. The fact that the Volume control works is indicative of that pot's connections being good, meaning that a variable resistor is connected between that shorted input/output line and ground.  Rotating the control works to increase or decrease that overall resistance. However, I'd lay decent odds that it's not smooth, that it has little effect until nearly to the end, and then WHAM!, it's all gone. Am I correct?

It also tells me that since the circuit is powered up for testing, there are no active components between the control and the output jack. At that point in your testing regimen, you should try creating the direct short between input and output, then listening to the output volume.... with the circuit powered off.

The Gain, Tone and any other controls, being on the far end of the variable resistor (aka the Vol control), won't have any effect at all, regardless of active or passive components in the signal path.

Put some images up for us to look at. Various angles, close and not-so-close, you know the drill. Include the schematic, if you're not worried about copyright and all that stuff. Not posting it will be fine, but may slow down one or more of us as we attempt analysis.

HTH




sumgai

[frets]

Sumgai😻,

Thank you for responding so quickly.  It sounds like you have had some experience with this happening too😸.  You’re exactly correct about the volume.

One of the pedals I’m doing for gifts for my friends is John’s overdrive pedal.  It is one that does not work.  I have one on a Vero board that works fine.  It’s just this one on the pcb board that does not work unless you touch the input output (somewhat).  

I’ve got the pots on leashes (wires), it’s how I do all my pots on pedals.

Here is the diagram.




And here is the board.




I don’t see an error.  I’ve looked at it until I’m blue in the face.

As always thanks Sumgai (and guys).

[JohnH]

I haven't built a pedal in quite a while, but when I did, they rarely worked first time! Then my troubleshooting, after looking for obvious errors, is to check dc voltages relative to ground. See if places that should be at battery + voltage are so, and at the output lug of transistors, (depends on tbe circuit) see if they are correctly at a mid voltage so they can swing up and down with a signal.

EDIT...oh hello little circuit! nice to see you again!

[JohnH]

Pinout problem...!

The input lug of the jfets, ie the 'Gate'...is not the middle lug.

microcontrollerslab.com/2n5457-n-channel-jfet-pinout-examples-features-datasheet-applications/

[thetragichero]

yup almost certainly a pinout issue

if you're serious about building pedals i would highly suggest seeking out an old, slow, 'boat anchor' oscilloscope (i enjoy my tek 453). local ham radio club would be a good place to start, somebody might just have one gathering dust in the basement

yes, an audio probe can be used but frankly my ears don't like to listen to that kind of noise when i'm already frustrated that the durn thing isn't working

[frets]

John,
Im confused, for example, the diagram shows the middle lug as accepting the “in” 56nF/1.5M.  So on the first 5457, it appears on the diagram that the 15k runs into the first pin, the 56nF/1.5M into the second and the 3.9k off of the 3rd to ground.  That’s not correct?

[JohnH]

It's just that the conventional schematic symbols, as on my diagram, don't necessarily correspond to the actual physical pinouts. Need to refer to the pinout data (see link in previous) to make the translation.

[frets]

Thanks John,

I vaguely remember this on the breadboard.  This will affect all the JFET boards I’ve made.  I’ll just have to do a little cross leg magic without having them touch.

BTW - this is my favorite overdrive pedal.  I’m not beaming just telling the truth.  I have used the Vero board version at all of my gigs and recording.  It has just the right amount of grit to it.

I also like the OCD which uses 2N7000 transistors for its clipping.  I think Yogi had mentioned it regarding its configuration.  

I believe at one time I had asked what everybody’s favorite pedal is.  I’d like to know what overdrive pedals are guy’s “go to” overdrive pedal?

One can’t have enough overdrive pedals😸😸😸

[Yogi B]

Dec 30, 2022 11:32:10 GMT -5 frets said:

So I have to check the gate pin for every transistor then design the board appropriately?

I see you've since deleted this, but here's my answer anyway.

For PCBs for DIY purposes it's quite common to see transistor footprints with four pads, i.e. including a duplicate of one such that it's compatible with a wider selection of parts. See for example the transistors (located mid left) of aionFX's Andromeda Natural Overdrive (their version of the Nobels ODR-1).

Which includes four-pad footprints for both a JFET (Q1, DGSD) and a BJT (Q2, ECBE). You'll obviously still need to check the data sheet to figure out the correct set of holes to use (and ignoring the 'semi-circular' placement suggestion, as appropriate), but the advantage is that you shouldn't have to redesign the PCB.

Occasionally you still might find some oddball part which still doesn't conform, the only JFET example I've made a note of is the 2N5460 / 2N5461 / 2N5462 series which has the drain in the middle, but if it's happened once...

---

I don't know if it is actually part of official standard for the packages, but surface mount transistors are (AFAIK) uniform across their technology (and package). For example, in the SOT-23 package, JFETs and MOSFETs have reversed pinout with respect to each other, despite both sharing the same terminal names, but:

• all SOT-23 JFETs share a common pinout — looking from the top, orientating the device such that the side with two pins is facing left and reading counterclockwise from the top left, we have D S G;
  
  
• likewise, all SOT-23 MOSFETs are G S D

[JohnH]

Hi Cindi, great! I'm glad that's cleared up, and very happy that you like this circuit!

It was my favorite OD too, until my build developd an issue and I've never gotten it fixed!

I like OD's too. My favorite ever is a Boss OD3, which is very thick and amp-like. After that, I'd list my Hardwire CM2, and also a Marshall Guv'nor II and a Boss Sd-1, both with my circuit mods.

[MattB]

Dec 30, 2022 13:22:17 GMT -5 Yogi B said:

• all SOT-23 JFETs share a common pinout — looking from the top, orientating the device such that the side with two pins is facing left and reading counterclockwise from the top left, we have D S G;
  

All the SMT JFETs I have datasheets for are S D G, not D S G, with the exception of the MMBFJ201, which is labeled D S G but specifically notes that drain and source are interchangeable, and so can be used with S D G pinouts.

J201:

J113/2SK208/2SK209/2SK3557/MMBF4091:

[marc121]

Frets -- may be on the wrong thread, but are you making/selling any hybrid telecaster harnesses ?   Thanks, Marc 

[newey]

marc121-

Hello and Welcome to G-Nutz2!

may be on the wrong thread, but are you making/selling any hybrid telecaster harnesses ?

Yes, it is, but there really isn't anywhere better I can move it to, as you're directing this to frets personally. Better to send her a PM with this question, it would only be happenstance if she were to note your response to this particular thread. Also, when posting, if you want to "tag" someone so that they know you have referenced them, insert a "@" symbol in front of their username, the member will then get a notification when they next log in. That was how I tagged you at the beginning of this post, and also tagged frets (where you see her name in blue).