Angry Andy Plus (JHS AT+) issue - muffled sound

[toto_]

Hi guys,
I just finished the Angry Andy Plus, the boost side works fine but I'm getting a muffled sound on the drive side (left side) and it's fuzzy when the drive is at 100%.
D4 and D5 don't light up when the drive is at 100% and when my guitar's volume is at 100% (same behavior on the 3 positions of the toggle switch, I guess they should light up on the up position).
The volume, drive, eq and air pots affect the sound but the toggle switch doesn't affect the sound when I switch position.
I don't know where to begin to troubleshoot. Any advice?

 

[toto_]

I just did some more (weird) tests : if the in and out jacks are unplugged and the toggle switch is down, D4 and D5 light up when I touch the tip of the in jack. It stops if I touch the ground of the in jack with another finger. Probably a ground issue, any ideas?

 

[Nostradoomus]

Set your multimeter up for continuity, clip one end to your white ground wire at the top and check all your ground connections. I’d start with the middle lug of your toggle switch, all three of those look like they may be cold joints.

 

[toto_]

Thanks for the reply.

I finished checking the ground connections and I didn't find any issue. The middle lug of the toggle switch is connected to ground, same for the ground lug of the in and out jacks. So all the ground connections seem good. I checked continuity between D4, D5 and the toogle switch (down position), and between D1, D2 and the toggle switch (up position), everything's fine.

So I did another test by plugging my guitar to the in jack, the out jack to my amp, drive pot all the way up, same for my guitar's volume, toggle switch down, and I noticed that D4 and D5 light up only when I play the big E string of my guitar. Looks like only the low frequency get through the circuit. It's probably why I get a muffled sound.

Measurements of the IC :
1: 4.79V
2: 4.82V
3: 4.42V
4: 0V
5: 4.59V
6: 4.59V
7: 4.37V
8: 9.17V

Any suggestion?

 

[Nostradoomus]

Your voltages are good. Probably a cold solder joint somewhere between the IC and your clipping diodes, something is choking it out. Maybe use an audio probe, if you don’t have one they are very easy to make.

 

[zgrav]

I'll second Nostradoomus. Look for a bad solder connection somewhere in the audio path since a bad connection could be blocking anything less than your strongest audio signals.

 

[toto_]

First time I use an audio probe (this article helped me: https://www.coda-effects.com/2015/07/troubleshooting-guide-for-guitar.html), very useful technique
I used a looper to get my input signal. Everything's normal until R7 : the sound is normal at R7 input, then there is no sound at R7 output (same for IC pin 6, C6 input and R8 input). And I get a muffled sound at IC pin 7, C6 output and R8 output. There's continuity between R7 and IC pin 6, C6 input and R8 input.

So I unsoldered C6 to check its value and I found the problem: it's a 100n capacitor... I'll check later if I did the same mistake on C3. I'll receive 100pf capacitors at the end of the week, I'll let you if it's fixed my issue.

 

[zgrav]

Nice job troubleshooting the build. Good luck with replacing the caps and having it kick into gear!

 

[toto_]

Thanks I've learned a lot of things.
I can't wait to received the caps. I love Andy Timmons sound so I expect a lot from this pedal.