Arachnid V2 Bypass Sound Only Troubleshooting.

[Walter]

Hi,

I am trying to assemble an Arachnid V2 pedal but am encountering some difficulties. When I plug the pedal into the amp and guitar the bypass sound works and the LED on the pedal lights up but no effect is created.(I did try reversing the amp and guitar cables connected to the pedal) This is my first time assembling a guitar pedal so I likely made an error in the build.
I do have a working Arachnid V2 that I copied the wiring diagram from.

Does anyone know what the problem could be?

Thank you so much.

 

[carlinb17]

congrats on getting into building pedals, and welcome to troubleshooting…

I would start with looking into trimming your leads, reflowing, and cleaning the flux. Also ensure your off board wiring is correct and cleaned up.

Is there any reason you did not use a socket for the eeprom?

 

[GizzWizzKing]

The ground pad for the eeprom looks like it may need a bit more solder flowed.

 

[Walter]

I checked all my solder connections and they all seem good. I reflowed the solder on the ground pin for the eeprom chip.
Unfortunately this didn't solve the issues I have been having.

Does anything else seem wrong about the solder connections and off board wiring?
Let me know if I should post more pictures.

 

[PJS]

Did you solder the FV-1 yourself?

Have you checked voltages to the ICs. If so what results did you get?

Do you have an audio probe? If not you will likely need one.

 

[Walter]

I purchased the FV-1 pre-soldered.

TL074CN
Pins 1, 2 ,3,5,6,7,8,9,10,12,13,14 all read around 4.2 volts. Pin 4 reads around 8.5 while pin 11 doesn't have any voltage.

FV-1(I tried my best with these measurements, if there are any critical pins that I should probe let me know)
pins 1,2,3,9,15,16,21 all read 1.6V. pins 4, 7,11,12,25,24,26,27 read zero volts, pins 5, 6,8,13,14,17,20,18,28 read 3.3v. Pins 10,22,23,19 read 0.8v

I do have an audio probe, are there any specific pins I should probe?

Thanks for the response,
Walter

 

[PJS]

OK, I haven't sat down with the datasheet and looked at every single pin, but that is looking about correct.

One question before you audio probe, where is your mix control set? Try it at one end, and then the other end. Are you getting sound at either extreme of the mix control (with the pedal engaged). If so is it clean or effected sound? Maybe try a reverb patch or similar so you can really hear if it is clean or not.

 

[Walter]

I tried the pedal couple more times and here is what I discovered.
When the pedal is off the guitar sounds fine. When the pedal is turned on only the effect of the pedal is being amplified(you cannot hear the guitar). I ran the exact same settings on the working pedal and with the pedal on the guitar and effect is amplified.

 

[Walter]

Both bottom potentiometers read 4.28 volts despite what setting they are at.

 

[PJS]

So you are getting the effect sound but not the direct sound? If that is the case that is really good news, because there's not many places that could be the problem then. The direct sound splits from IC1 pin7, and goes through C6 and R4 to the mix pot. If you use the audio probe to follow that through and find out where the signal is being lost then you will be able to look in that area for poor solder/shorts etc

 

[Walter]

It has been a while, here is an update.

I got the pedal to work. I don't know what did it though. I just plugged it in one day and it started working.

So I put it into the enclosure and now I am essentially back to square one. The sound works, but no effect. What is different from my original situation is that the LED doesn't light up.
I will continue troubleshooting soon, I just want to give an update.

Thanks for you're continued help,
Walter

 

[PJS]

Has to be power or the switch. I am betting one of the wires broke with the handling. Hopefully it is an easy find and fix for you