All out of ideas with the 3 legged dog.

[domkekp]

OK I don't like to accept defeat, but I built the "3 legged dog" from www.home-wrecker.com.  The links to the Schematic and the files that I used are here:
http://www.home-wrecker.com/3leggeddog.html
http://www.home-wrecker.com/3ld-new.pdf

The distortion sounds good but only when I crank the volume of the pedal all the way up and turn up my amp just to hear it.
Admissions:  I am a beginner and may have bit off a little more than I could chew.  I wanted to learn everything that I can so I etched my own board, and did everything "by the book"  mostly because I didn't know where I could deviate.  All parts exactly as specified and confirmed in the right place on the circuit board.  I have also used the audio probe throughout the circuit, but to be honest I am beginning to understand opamps, but this CD4049UBE – no clue.  The JFET and the IC are oriented on the board as shown in the 3ld-new.pdf at the above link.

Also, here are some pictures of the build.  They may or may not help you.
http://www.flickr.com/photos/ken_domke/sets/72157629878804785/

Here are some voltages.  (Using a Walwart.)
Supply Voltage 9.25V
Q1 J201 JFET
D-3.15V
S-.35V
G-0V

U1 CD4049UBE
1-9.25V
2-3.57V
3-3.33V
4-3.90V
5-3.52V
6-6.39V
7-2.87V
8-0V
9-0V
10-9.24V
11-0V
12-9.24V
13-0V
14-0V
15-9.24V
16-0V
Positive side of C2 .34V, C5 3.56V
If you need more info, I'll get it to you.       Thanks, Ken

[Vince_b]

I'm not really good at readind voltages so I cannot help you with that.
But I suspect that your problem might possibly be a solder bridge somewhere on your pcb.

To me the best way for debugging is using an audio probe.
http://www.diystompboxes.com/pedals/debug.html
You just have to follow the signal path from the input to the output and you will be able to see where you are loosing the signal (or where it is becoming very weak). When you find the spot where things are going bad, look for solder bridges, wrong components value or burned components. This way you should be able to figure what is the problem.

I hope this will be of some help.

[Earthscum]

Quite honestly, all your voltages look about right. Double (and triple) check your in/output wiring to the stomp switch. My suspicion lies there... common mistake to do things like turn your 3PDT 90* from where it should be (guilty as of about a month ago   ). Also, if you are using a switching (stereo) input jack, make sure you are actually soldered to the tip and not the center (ahem... another one I did... same build).

Does your gain pot react the way it should (from what you can hear, anyways)?

ETA: See the trace where the output cap connects to, and R9 comes off of to ground? Check that clearance. It may be close enough to bleed signal, and if there's any flux left over, it can contribute to the problem. Check the board for other gaps that may have closed in, as Vince suggested, but that area looks suspicious to me. Can't see the bottom of the board post-solder, so I can only make the assumption here. Good luck!

[domkekp]

First off, thanks for the quick replies.

OK checked the wiring on the 3PDT switch, it looks good according to the Beavis Audio stompbox wiring here:

http://www.beavisaudio.com/techpages/StompboxWiring/
(bypass works and you can hear the distortion audio when switched, just at extremely low volume)

The wiring to the jacks is good. To make you feel better I did that when I first built the pedal.  Thank God I found that early on.

Used a small flathead screwdriver to ensure there was no hidden connection between unconnected traces and cleaned it thoroughly with some alcohol and a small paintbrush.  Rechecked all continuity and it seems good, but I'm not sure about the proximity piece.  I'll check with the audio probe tonight after work --dang grandkids are here and still sleeping  I'll report the findings when I get it done.

BTW thanks for the voltage check.  Looked everywhere for transistor/IC check voltages for this thing like ggg puts out for their pedals.

Ken

[Earthscum]

To give you a basic idea with cmos, inverters (you are using a UB, right?), when you use a feedback resistor, they self bias, unlike opamps that need a reference voltage. You can kind of think about an inverter (NOT gate) as a pair of resistors between V+ and GND with the centers tied together.

Now, when you look at it like that, if the gate goes high, the "resistive divider" (inverter) makes the voltage go low. If you have them tied together through a resistor, the output going high tries to correct the input's low state. Therefore, if an inverter has no point of bias, it should be around half of V+ at the output.

If you take the gate and tie it to ground through another resistor, as in the first 2 stages, your output is going to be at a different state because it's trying to self-balance. The gate on U1 is going to show you different voltages depending on where the gain is set, but it generally should be somewhere between 1/3 V+ and 2/3 V+.

The reason the stages aren't all self-biasing is because it causes the inverters to bias into a different operating region, which adds to the characteristic sound. It's like biasing jfets and transistors into their different operating regions to create different characteristics in the way they process the signal (which you'll probably get into at some point if you haven't already). Careful... I find inverters to be really addictive. They are awesome fun to play with once you know the "rules" that they like to play by. 

[domkekp]

First off thanks for the info on the 4049 Earthscum, it has actually given me a couple of ideas once I'm finished with this thing.  Also, sorry it took me so long to get back, finally got back over to the bench.

Anyway, I found the break with the audio probe at C4.  I fixed that but now I get a hideous squeal at the mid range of the gain pot.  When you go high or low it goes away.  Also, it comes back if you unplug the guitar??

Do I have a jacked up gain pot or something?  Man, this thing is killing me.

Ken

[domkekp]

I may be looking at this issue all wrong but I've got a couple of ideas.  I read on some other threads that there should be 4.5V at the drain of the JFET. 

http://www.diystompboxes.com/smfforum/index.php?topic=231.msg1900#msg1900

Right now it's sitting at just a touch over 3.1V.  I have also read that this thing squeals like a pig with low voltage.  My input Voltage is fine, but I'm wondering if my drain voltage may be a symptom of the problem.  I wonder if it is a problem with the original specs and I should be troubleshooting the R1 value.

With that said, tonight I'm going to try connecting a 100uf cap across the input power to see if the wallwart is the cause of the squeal.  It may work, but I wonder if I'm just putting a bandaid on an internal issue.  Any thoughts?

Thanks.

[KBG]

I may be looking at this issue all wrong but I've got a couple of ideas.  I read on some other threads that there should be 4.5V at the drain of the JFET.  

http://www.diystompboxes.com/smfforum/index.php?topic=231.msg1900#msg1900

Right now it's sitting at just a touch over 3.1V.  I have also read that this thing squeals like a pig with low voltage.  My input Voltage is fine, but I'm wondering if my drain voltage may be a symptom of the problem.  I wonder if it is a problem with the original specs and I should be troubleshooting the R1 value.

With that said, tonight I'm going to try connecting a 100uf cap across the input power to see if the wallwart is the cause of the squeal.  It may work, but I wonder if I'm just putting a bandaid on an internal issue.  Any thoughts?

Thanks.

Did the cap fix it? I have used a 220uf from pin 1 to pin 8 to stop oscillation.

[R.G.]

It's really never OK to not use a power supply bypass. DC power supplies need decoupled near where the AC is being generated. This is especially true the higher the impedance of the signals (... those 470K, 1M, and 2.2M resistors for instance, on the MOSFET inputs) and the higher the gain, and the higher the frequency response of the parts. A CD4049 in linear mode goes up to many megahertz.

Get a 0.1uF *ceramic* cap from +9V to ground as nearly on the chip pins as you can. Then put a 22uF or bigger from +9V to ground somewhere. Only after than can you tell what's going on with the chip. It *may* be oscillating at a few MHz.

[Earthscum]

Get a 0.1uF *ceramic* cap from +9V to ground as nearly on the chip pins as you can. Then put a 22uF or bigger from +9V to ground somewhere. Only after than can you tell what's going on with the chip. It *may* be oscillating at a few MHz.

I like to try and tuck a .1u (C) under the socket. EB used to have some DIP sockets with a mono cap installed already, and I figured out that little space inside is perfect for hiding it. Usually takes that part out of the equation when I'm designing a layout.

I was looking at yours, and if I were to put a cap in after the fact, I would use heat shrink on the cap leads and drill through right next to the V+ and GND pads on the IC, and tuck in right beside the socket.

OR... it looks like you could do the same from the backside and tuck it between the IC pins to keep it from bumping off the foot switch. I hardly ever have a problem re-mounting resistors and flat components to the back. Usually they don't exceed the height of the protruding pins by too much.

[domkekp]

Not a whole lot of time tonight, but I did find that I had a cable that was going bad.  I think that was affecting things when I was messing with the gain pot.  It now only seems to squeal when I disconnect the guitar.  I'll try to install the caps tomorrow night and I'll report back then.  Hopefully with good news.

I was looking around and I'll probably put them both on the bottom.

[petey twofinger]

i built one for Deet (my lil kid) and it was sreeching .

i tried monkeying around w/ switchable input caps , which worked but killed the high end`. then i went thru this thread and tried eveything, which nothing worked until i got to what RG said about the .1 ceramic on pin 7 to ground .

bingo . thanks Rg !!

i may keep the switchie caps ....

gonna try some different pots cause i didn't care for the (non existant) sweep .

wish it has a tone cont , you cant add one here can you ?

if you can whats the least "gain-stealinest" ?

id love a mid scoop , is that possible ?