Snarkdoodle problem...

[dorrisant]

I built the Snarkdoodle 2012 Edition.

I can trace signal to the input side of the CD4049 pin 5, also C4 and R5. No signal on pin 4. I have pulled C4 and R5 and confirmed their values as well as C5. I did make my own pcb from the document... All traces look fine , no crossed traces etc..  Does this sound like a bad chip?

Thanks in advance for any help...
Tony

[dorrisant]

I guess I should post some pictures...

Can anyone post the chip voltages?

Tony

[mgwhit]

If you've got another 4049UBE laying around, feel free to try it, but on an etched board a bad component is the last thing I would suspect.  It's probably just  a short or a bad joint. Without seeing it, I suspect you may want to reflow your joint on (at least) pin 4.

Please upload good pictures of both sides and I would be happy to take a look.  I'd check my voltages, but mine is at my practice space right now.  In the meantime, go ahead and post your own.

[dorrisant]

Thanks !

I will post some pics when I get back to the bench later today.

Tony

[dorrisant]

Ok... Here some pics of my build.

I did install the boost switch with 100k/10M resistors.

The in/out jacks function correctly, it passes signal just fine when it is in bypass. The #2 and #3 terminals of the gain pot are tied at the pot (no need for that wire).

Tony

[dorrisant]

I cut these pics down to half size... Still pretty big.

[dorrisant]

I cut the ends of the board off... Had to fit it in the box.

[dorrisant]

The other end. I put a light behind to shine through the board.

[mgwhit]

Thanks for the backlit trace photos.  The place that looks most like a short is actually the ground and 9V pads at the top!  I'm guessing that's probably not the case, but you need to check your voltages ASAP.  Is the signal you're probing at pin 5 at all amplified?

[mgwhit]

There are a couple of dodgy joints on pin 7 and R3, but I doubt those would cause your problem.  Check for continuity between pin 8 and the positive leg of C5.  There's some detritus on the board there, and a short to ground in that location would totally explain your problem.

[dorrisant]

There are a couple of dodgy joints on pin 7 and R3, but I doubt those would cause your problem.  Check for continuity between pin 8 and the positive leg of C5.  There's some detritus on the board there, and a short to ground in that location would totally explain your problem.

No short there... Meter shows 20 megs and climbing.

Voltages:
1- 6.67
2- 2.99
3- 2.91
4- 0
5- 6.11
6- 6.88
7- 0
8- 0
9- 0
10- 6.68
11- 0
12- 6.88
13- 0
14- 0
15- 6.68
16- 0

Reflowed all joints and  pulled the chip and socketed it. Tried two more with the same results.

Tony

[dorrisant]

If I lift the ground side of C5 I get signal through it. Using my Behringer CT100 I get .135vac at the input and .115vac at the ground side of C5 with the  gain maxed. I have now tried 4 different chips and find it hard to believe that all are bad. I have rechecked all the values of components.

I have built hundreds of pedals... Many are way more complicated than this.

I am at the point where throwing the whole thing at a wall and watching it explode is starting to sound like the only way to achieve any satisfaction from this project.

At my wits end...

Tony

[selfdestroyer]

I am sorry to hear you are having so many issues with this build but let me reassure you, if you get it fixed it will be the best feeling you can have. That being said don't give up. With such a low part count you may want to replace parts as you trace it.

But.. there is a time to throw in the towel and just etch another board. I have been there before. I built 2 cavedwellers once and both would not work and gave me the exact same issues. I later found out that my 1K resistors got mixed up with my 100k resistors (if I am remembering correctly)  and caused disaster.

Hope it works out for you.

Cody

[mgwhit]

Thanks for posting your IC pin voltages.  First off, that 6.67V on pin one looks crazy low.  Are you running this off of a battery or a wall-wart power supply?  What voltage are you getting at the +9V in pad?

Second, and perhaps most important, your pin 4 is at 0V, probably shorted to ground.  Power down and test for continuity to ground there.

[dorrisant]

Using a One-Spot , the only pedal loading it... 9.54v.

No continuity between pin 4 and ground.

Three out of four of the chips I have show 1.4v on pin one...

Just for S&Gs I replaced R7 with a 1W MF... I have changed and confirmed values on all of the onboard parts at least three times... Oh, I'm not giving up.

One of the chips showed 6.7v or so... None of them show any voltage on pin 4 at all.

Hmm... Thanks to all for the comments, you are all helping me preserve some sanity. I definitely need that right now. 

Tony