SOLVED Aion Onyx (Boss Slow Gear) - Pedal Turns On but No Effect

[apierz]

SOLVED:
For Q2 I was using a through hole K30A transistor which uses a pinout that does not match the placement of the holes on the pcb and so I had soldered this part incorrectly.

After correcting my mis-soldering, I used this method from @Jeffrey to set the trimmer pot and get the pedal working properly:

I built this same pcb and it was useless until I learned how to set the trimmer. If the trimmer isn't set almost perfect this circuit won't work at all. Get it right and this pedal is awesome......set up the pedal as if you're going to play but leave the bottom plate off so you can reach the trimmer. Turn your guitar and pedal on. Turn attack knob to 12 noon. Turn the speed all the way down. Make sure the pedal is engaged strike a chord and slowly adjust the trimmer. Keep striking a chord while you're adjusting. As soon as you hear your guitar go silent for a split second and return to normal stop adjusting...trimmer is set... dial back the knobs until you figure this pedal out.. if the knobs are to high the effect is so fast that it's useless because you can't hear it. I tried adjusting with a multimeter to their recommendations. But this pedal sat in my closet for months because of a trimmer.

Original Post:
I recently completed my build of an Aion Onyx. When I turn on the pedal, the LED turns on but it has no effect on the sound with any combination of knob and switch settings. There may be a very slight volume drop with the pedal engaged, but otherwise it sounds like bypass.

I made one modification to the part list: Q2. Aion lists a 2SK208-GR to replace a 2SK30A-GR that was used in the original pedal, but I had an easier time finding a 2SK30A so I used that instead. Also, I wired my power jack to a ground on the switch PCB rather than merge it with the audio grounds Aion uses in their wiring diagrams. I used my ear to set the trim, which for me got the highest output with it set fully counter-clockwise.

Here are my voltage measurements for the diodes, transistors, and IC:

D1
A: 8.84
K: 8.61

D2
A: 3.325
K: 3.437

D3
A: 3.318
K: 3.385

D4
A: 3.321
K: 2.892

IC1
1: 5.5mV
2: 4.203
3: 4.143
4: .1mV
5: 4.4mV
6: 4.372
7: 8.14
8: .5mV

Q1
C: 8.45
B: 3.748
E: 3.318

Q2
C: 5.013
B: 5.440
E: 5.010

Q3
C: 8.46
B: 6.56
E: 6.47

Q4
C: 5.280
B: 3.515
E: 3.244

Q5
C: 3.368
B: 3.440
E: 3.294

Q6
C: 3.354
B: 3.365
E: 3.289

Z1
A: 0
K: 5.437

Here are pictures of my build, and of the documents from Aion: https://aionfx.com/app/files/docs/onyx_documentation.pdf

 

[Jeffrey]

I recently completed my build of an Aion Onyx. When I turn on the pedal, the LED turns on but it has no effect on the sound with any combination of knob and switch settings. There may be a very slight volume drop with the pedal engaged, but otherwise it sounds like bypass.

I made one modification to the part list: Q2. Aion lists a 2SK208-GR to replace a 2SK30A-GR that was used in the original pedal, but I had an easier time finding a 2SK30A so I used that instead. Also, I wired my power jack to a ground on the switch PCB rather than merge it with the audio grounds Aion uses in their wiring diagrams. I used my ear to set the trim, which for me got the highest output with it set fully counter-clockwise.

Here are my voltage measurements for the diodes, transistors, and IC:

D1
A: 8.84
K: 8.61

D2
A: 3.325
K: 3.437

D3
A: 3.318
K: 3.385

D4
A: 3.321
K: 2.892

IC1
1: 5.5mV
2: 4.203
3: 4.143
4: .1mV
5: 4.4mV
6: 4.372
7: 8.14
8: .5mV

Q1
C: 8.45
B: 3.748
E: 3.318

Q2
C: 5.013
B: 5.440
E: 5.010

Q3
C: 8.46
B: 6.56
E: 6.47

Q4
C: 5.280
B: 3.515
E: 3.244

Q5
C: 3.368
B: 3.440
E: 3.294

Q6
C: 3.354
B: 3.365
E: 3.289

Z1
A: 0
K: 5.437

Here are pictures of my build, and of the documents from Aion: https://aionfx.com/app/files/docs/onyx_documentation.pdf

I built this same pcb and it was useless until I learned how to set the trimmer. If the trimmer isn't set almost perfect this circuit won't work at all. Get it right and this pedal is awesome......set up the pedal as if you're going to play but leave the bottom plate off so you can reach the trimmer. Turn your guitar and pedal on. Turn attack knob to 12 noon. Turn the speed all the way down. Make sure the pedal is engaged strike a chord and slowly adjust the trimmer. Keep striking a chord while you're adjusting. As soon as you hear your guitar go silent for a split second and return to normal stop adjusting...trimmer is set... dial back the knobs until you figure this pedal out.. if the knobs are to high the effect is so fast that it's useless because you can't hear it. I tried adjusting with a multimeter to their recommendations. But this pedal sat in my closet for months because of a trimmer.

 

[PJS]

It looks to me as if 2sk208 and 2sk30 have different pinouts, so you will have to take that into account if you are substituting

 

[apierz]

Thank you both for helping on this old thread. @PJS, I never would have caught the pinout issue on that transistor if you hadn't pointed it out. I was able to switch the source and gate pins and use @Jeffrey 's advice to set the trimmer and now it's working great. It's definitely a finicky pedal but I'm sure I will have fun figuring it out.