BYOC Envelope filter not working

[jable1066]

Hi, this is my first build and everything originally was going great and the pedal was working. I then went and swapped out the LED as I'd soldered it in too close to the board so it wasn't popping out of the case - bad idea, as now it doesn't work. The LED comes on and bypass is fine, but I get no response from the pots - no effect. I have tested all the connections and de soldered all the off board wiring and re soldered it all and tested it again - twice. Everything is connected and there are no dry solder joints. I don't have access to a camera right now as my girlfriend has it on holiday so I was just hoping for someone to shed some light on the readings I obtained from it.

While connected to a 9v power source I put my black probe from my MM to ground (first the screw holes of the enclosure and second the ground connection on the input jack). My first lot of readings gave me 0's for every leg on the OPamp and the Optocoupler. When I tried with my ground probe at the input jack every reading was above 8v - that is for each leg of the OPamp and optocoupler. I then put my black probe to the ground on the output jack and got readings of 0's again.

I went on to try this without a 9v power source and got 0v readings for everything - not sure if I had to do this but thought I should anyways. It might be worth mentioning that I burn't the top of a 0.01uF cap while replacing the LED - the top is slightly caved in by the heat of the soldering iron - could this effect the EFFECT?

I'm not sure what else I can test - I tested all the pots before putting them in and they were fine - every connection was tested throughout the process and again at the end - all solder joints have been checked, re checked and checked again. Wiring was followed as per instructions and checked again and again and again. If anyone needs more info I will post more - also pictures may be possible with my phone camera however its resolution is poor and I think that to see any detail from the pictures just wouldn't happen.

[Fender3D]

Whenever you can't measure any tension running on PCB, then you have NO tension running on PCB...
This may seem silly , but you have NO tension on your PCB.
Check VCC path until some volt appears on the board

[Schappy]

Read This
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Build an audio probe. Use it to test your signal through the circuit.

Did you ground everything the input jack? If so you can use this as your ground point. Otherwise use the ground on the board.

Are you saying that after you got 8V readings from your Opamp you took a reading just from the input jack?

If so you need to have the red lead connect to a part that is getting voltage and the black to ground.

First thing I always do is check that I am getting 9v into the board.
This way you start at your voltage source and continue on until the problem is found.

Start with the red lead of your DMM on the 9v adapter jack where the  input wire is attached. Black lead on ground.

Are you getting 9V?

If not then you know the problem starts there. Otherwise continue on the the input wire on the board and get a reading.

Are you getting 9V?
If you are then take readings from the opamp and list the voltage at each pin. Hopefully your project lists the correct voltages so you can compare.

If you are not getting any voltage then there is a short somewhere between the input and the opamp.
If you are getting weird voltages then you may have a bad connection or bad solder joint somewhere.


Im still a beginner but have debugged several circuits with the debugging thread and an audio probe.

The only way to consistently debug circuits is to mentally go through it in a flowchart like manner.

[jable1066]

Hi, thank you both a lot for replying so quickly. I have my DMM and an SRV dvd with me now so I'm going to be patient and check voltages. I'll post up what I get when I finish or if I have any problems.

Jonny.

EDIT: EDIT: I didn't have a cable in the input... the new voltages have been updated

Receiving 9V DC to input AND to 9V pad on the circuit board

Op amp - in brackets are the voltages measured by someone on a fully functioning pedal on the BYOB board... they all seem to match up alright.

1 = 4.16 (4.6)
2 = 4.16 (4.6)
3 = 3.36 (4.6)
4 = 0.00 (0.0)
5 (directly opposite 4) = 3.54 (4.6)
6 = 3.88 (4.6)
7 = 4.14 (4.6)
8 = 8.31 (8.0)

Optocoupler

The side with 2 legs:
Positive pin (+) = 0.03
pin next to positive = 0.00

The side with 3 legs:
Reading from directly underneath or opposite + pin (depending on which way you look at it, going right -> = 2.86, 3.36, 4.11

I have decided the photos are way too blurry and I'll have to wait to take pictures untill I get my camera back. I will re-re-edit this post with the correct voltages from the BYOC board.

Another edit:

On the + of the Octo Coupler 1.2-1.5v, the one directly to the right of that, 0v...maybe a few mV, but nothing major. On the side with 3 legs, voltages were measured in the range of 3.9-4.3v

These are the measurements they are mean't to be... it seems my positive leg with the LED is not correct - mine reads close to zero... Hmmm.

1-3 were at about 4.6v, pin 4 was 0, then voltages on Pin 8 (opposite Pin 1) 8+v, then pins 5-7 around 4.6 volts.

My measurements for the OpAmp seem to match up with these, which were taken from the BYOB board.

Could my problem be lying in the + leg of the optocoupler?

[Fender3D]

When switching SW2 to manual AND turning VR3 the voltage at Opto's + should change, otherwise your opto is reversed.

edit:
no, your opto can't be reversed by itself.... 
check the burned capacitor, if you shorted the cap it will let DC pass through, leading to issues.
BTW
C1 is far away from LED, how did you burn it?

[jable1066]

I'm not sure how I go about checking the capacitor, or what I'm really checking for - my knowledge is very limited (something I'm working on). From what I've read I can check if it's blown but I'm not actually sure how... I think it got burned when I was desoldering the external wiring from the PCB. After it failed to work, rather than debug it like anybody with an ounce of common sense, I disconnected all the wiring thinking it was a problem solder joint that I couldn't be arsed to find. I have learned a valuable lesson in doing this, as I have now had to put it all back together when a bad solder joint was probably not the issue  ! Still, I've learned a lot about tidy off board wiring and how to wire everything up in a small enclosure. Anyway, I digress... how do I check the cap? I have built an audio probe and I'm going to have a long shootout with the circuit tomorrow. Stephen, a mod on BYOC has given me some good information about what I should test for with the probe so I'll re-post after I have checked everything there. Thanks again for the help.

[Fender3D]

you can check the cap with ohm meter:
it should have infinite resistance.

Anyway you're just 2 solders away from replacing it

[jable1066]

I checked the resistence of the cap by setting my DMM to the highest resistance setting (2M)... I then probed the cap and it showed a 1... as was before I probed it. Am I right in thinking that this is normal... I'm not too capable with the DMM yet but I think that's what it should be... anyway... I checked my voltages of the Optocoupler and did some probing... The + leg of the opto is showing a really really low voltage - 0.07 when it should be around 1.5. I probed the OpAmp legs and I should have been hearing the wah/automatic envelope filter sound at pin 1 when I plucked the guitar. I did not hear this, but instead heard a clean signal. Could the faulty optocoupler be effecting the way the OpAmp behaves?

[Fender3D]

When opto doesn't work = no wha effect
ok
but you should ask yourself what might have kill the opto?
If the pedal worked untill you mess with the LED, then (burned cap aside) nothing would harm it.

Watch out those darn wires gang, or switches mob they 're the first and usual suspects in a pedal murder.

BTW
when turning VR1,2,3 does anything happen?

[Paul Marossy]

My guess is that the PCB was damaged when you tweaked the LED, not hard to do, especially if it's a single sided board. Look for broken tracks and/or lifted pads in that area. Check for continuity. And check for cold solder joints. Sometimes I have solder joints that look like they should be perfect and they are actually cold solder joints.