please help me debugg this red llama clone...first debugg!

[themosscollector]

Ok..i have built pedals way more complex then this but i havnt really had to debugg yet. This red llama i am working on is passing signal when disengaged but nothing when engaged.

Layout i used: http://1.bp.blogspot.com/-W_R9JJaQ-X0/T8yUiIoEoAI/AAAAAAAABmk/3UWnQ_C3Uv8/s1600/Red+Llama.png

Here are my ic measurments. It looks like the only readings that is off are pins 2 and 3.

9v at the board: 9.3

1: 5.3
2: 3.5
3: 0.4
4: 2.2
5: 2.2
6: 0
7: 5.7
8: 0
9: 5.7
10: 0
11: 5.7
12: 0
13: 0
14: 5.6
15: 0
16: 0

Where  do i begin? Any help would be greatly appreciated.
Thanks!

[aron]

The first thing is to find a schematic.
I would pull the chip and measure pin 1. Your voltage on pin 1 should be 9V but it's too low so you have some sort of miswire.
Also make sure your IC is oriented correctly.

[themosscollector]

Here is a schematic: http://gaussmarkov.net/layouts/redllama/redllama-schem.png

The diode is left out in marks layout

[mth5044]

I don't think that the schematic ='s the layout. In the schematic, pin 7 is grounded, but in the layout, it's getting supply voltage. It's really hard to tell what the orientation of the IC is in that layout, but I think I can see a very faint grey half circle on the top?

[themosscollector]

I pulled the ic and pin 1 measures 9.3v.

[themosscollector]

When i was looking for ic measurments online, i came across the ggg way huge red llama page. The measurments on their pins are pretty close to what i am getting (except pin 2 and 3).

http://www.generalguitargadgets.com/effects-projects/distortion/red-llama/

[thelonious]

It's really hard to tell what the orientation of the IC is in that layout, but I think I can see a very faint grey half circle on the top?

I think you're right - pin 1 is top left of the IC. In the schematic, the unused inputs are tied to ground; in the layout, they're tied to VDD.

It looks like the only readings that is off are pins 2 and 3.

That seems correct to me. VDD should be ~5.5v because of the 1K series resistor between it and +9V. It rises to 9.3V when you remove the IC because the IC is no longer drawing current, and no current = no voltage drop across the resistor.

Did you catch the double link under the IC? Next step I'd take would be to pull the chip, disconnect the power, and measure every resistor in place to make sure it's correct... try a different 4049... run a razor or x-acto between all your tracks... reflow solder joints on all the components near pins 2 & 3... etc.

[aron]

I think you are right. Pin 1 should be top left I assume. Good one on pulling the chip and measuring and testing. I had to do a similar debugging operation on my Moog.

[duck_arse]

I don't think that the schematic ='s the layout. In the schematic, pin 7 is grounded, but in the layout, it's getting supply voltage. It's really hard to tell what the orientation of the IC is in that layout, but I think I can see a very faint grey half circle on the top?

I very much agree with the first sentence.

looking at IvIark's layout, there is a note that even I can see, "Watch two links under IC pin7". that is a fairly good indication of which way is up, once you've spotted the double link itself. and yes, it should have the pip indicated better. it should also state the 4049 needs to be an un-buffered (UBE) version (or does everyone already know that?)

can we see photos of the offending board?

[themosscollector]

Sorry, i should have mentioned....i couldnt fine a schematic for marks layout so i just pulled up another Red Llama one, hoping it might help.

I measured all the resistors and they seem to be correct.
Unless i am missing something, I have the 2 jumpers in which meet and connect at pin 7( hole to the right of pin 7?)

here are some pics of the board. thanks for the replys.

[thelonious]

7th hole in from the left, between rows 3 & 4, is there a solder bridge between the strips, or is it clear? It's hard to tell from 2 dimensional photos on a screen.

Edit:
This spot is what I'm talking about. I can't tell if it's a trick of the light.

[themosscollector]

I just measured and got no continuity between those 2 points

it looks like a bridge in the photo but it is just a lead that was a little long on row 3. optical illusion

[duck_arse]

measure the resistance across pins 4 and 5, power-off, IC-out, while you twirl the drive pot, please. what reading do you get?

[themosscollector]

resistance between pin 4 and 5 measures 0.099m to 1.075m when the drive pot is turned

[themosscollector]

Forgot to mention that i substituted a 470uf 16v cap for the 330uf cap but i dont think that should effect anything.

[themosscollector]

I tried tracing the signal with an audio probe, starting at the input. It loses almost all the signal on the bottom of  point of the 100pf ceramic cap  (4th  row from the top). Only very feignt sound heard.

[mth5044]

For the drive pot, you have purple going to 1 and black going to 2 and 3 ?

[themosscollector]

Yes. Purple going to 1 and black going to 2 then jmper from 2 to 3. Is there any way to measure if this ic chip is busted?

[duck_arse]

try removing the 100pF cap. you'll be able to check the value of the cap and you might surprise a bad joint.

[themosscollector]

just pulled the 100pf cap and it measured .012nf (close?). put it back in and still have the same the same results.
i should also note that when my test amp is turned up loud, there is audio signal coming through, just very feint. volume and drive pot both effect the signal.

for such a simple circuit....this one is really frustrating me! hope i can work through it.