SOLVED Dirty Sanchez issue: LED not turning ON

[MatHK]

Hi, I have just finished my first PCB build. However, something is not right.

First, when the pedal is bypassed, it's all good, I hear my guitar through the amp.
When it's engaged however, the LED doesn't turn on (and no sound comes out of the pedal).

I first focused on why the LED was not turning ON. Here is what I did:
- I measured the voltage at my 9V DC jack. It shows 9.41V, so far so good.
- there is continuity between the + and R31
- R31 reads 10K ohm
- there is continuity between the other leg of R31 and the negative leg of the LED (the square on the PCB)
- then there is continuity between the positive leg of the LED to the ground
- the voltage on R31 is 0V: I would expect the resistor to drop the voltage and to be 9-1.8V

I tried to compare what I listed above with what I see on the schematic attached below.
On the schematic, the positive leg of the LED is connected to R31, while it's the negative one in my case.
I am unclear if I misread something or wired wrongly.

I used my multi-meter to check if my LED was wired the wrong way, but I really think I have it matching the PCB symbols: in continuity mode on the multi-meter, I can light the LED if I have the black probe to the negative leg of the LED and the red probe to the positive one.

I really appreciate any help to understand what is happening. Thanks!
Cheers

 

[zgrav]

if you have another LED, touch the leads on it to the points your LED is soldered to the board. try it in both orientations and see if it lights up either way when you press the footswitch. you could have your LED in wrong, it could be a bad LED, or you could have a bad footswitch. but -- if you get no sound when the bypass is off then you have other problems as well that you can sort out after you get the LED working.

 

[MatHK]

Thanks a lot. You are right, it lights up when I put another LED the way around on the soldering joints.
My LEDs are wired the wrong way. This thread here has all the info needed about LED (I basically used symbol #1 while symbol #3 was the one prevailing here). My bad, lesson learned!

As there are other LEDs in the schematic, they are wired the wrong way too, very likely explaining while I have no sound.

I will revert once I fixed this.
Cheers

 

[PJS]

The good news is that the other LEDs on the board are back to back pairs. It does not matter which way each LED is facing as long as each pair has one facing each way. Even if they were both one way you would get sound through, just the distortion would not be what was expected. The bad news is that this is therefor not likely to be the cause of the no sound problem.

 

[MatHK]

I went ahead and reversed all LEDs (I didn't see PJS's message before starting that).
It was better (I had some sound, not great though) but the LED was not turning off in bypass this time. I had to change the switch.

After all that, the LED now behaves properly and I do have a proper sound. I am not noticing a big effect when adjusting the internal trimmer though, I will further check.

Thanks for your help!