SOLVED Aion Andromeda - Bass not working

[Noodles]

Hi all. Long time listener, first time caller. My electronics theory/understanding is a bit shaky, so excuse any dumb questions (another thread to follow).

I just finished the Aion Andromeda from the PCB. It works fine aside from the Bass control. All the voltages on IC1 and IC2 are fine as they are on Q1. I've tested continuity from leg 2 of IC1 to the pot. Lug 1 to 3 of the pot measures 50K. Lug 1 to lug 2 measures 0 always. I measured the voltages at each leg of the pot. All the same. But, when I went from CCW to middle to CW with the pot setting, the voltage did not change on the wiper lug.

Can I assume I simply have a defective pot? Or, am I missing something?

Schematic here: https://aionfx.com/app/files/docs/andromeda_documentation.pdf

Bass control portion below.




If it's the pot, any pro tips on getting that ###### out of there? It's a pretty dense board.

 

[Giorfida]

Hi all. Long time listener, first time caller. My electronics theory/understanding is a bit shaky, so excuse any dumb questions (another thread to follow).

I just finished the Aion Andromeda from the PCB. It works fine aside from the Bass control. All the voltages on IC1 and IC2 are fine as they are on Q1. I've tested continuity from leg 2 of IC1 to the pot. Lug 1 to 3 of the pot measures 50K. Lug 1 to lug 2 measures 0 always. I measured the voltages at each leg of the pot. All the same. But, when I went from CCW to middle to CW with the pot setting, the voltage did not change on the wiper lug.

Can I assume I simply have a defective pot? Or, am I missing something?

Schematic here: https://aionfx.com/app/files/docs/andromeda_documentation.pdf

Bass control portion below.


View attachment 71848

If it's the pot, any pro tips on getting that ###### out of there? It's a pretty dense board.

Does the resistance between 1 and 3 of the pot change as you turn it?

 

[Noodles]

Hmm…good point.

CCW = 50K
Middle = 7.6K
CW = 0

 

[Giorfida]

Hmm…good point.

CCW = 50K
Middle = 7.6K
CW = 0

And of course I’d assume that pins 1 and 2 are tracking the same way with respect to pin 3 since 1 and 2 are tied.
If so then we know the pot is likely just fine… so it’s tracing other components in the path of the pot. While doing that, double check the capacitor value. Wrong value could make the bass roll off less effective

 

[Noodles]

Correct on the pot pins. Phew and doh!

Leg 2 IC1 to R8, R8 to pin 3 pot both have continuity. I will take the board out and check the pot to C5. C5 confirmed as correct value.

The bass roll off Is too effective. It is as rolled off as the circuit will allow, like it’s stuck CCW resulting in a too bright sound with nasally mids. It should sound pretty good once more bass returns.

 

[Giorfida]

Correct on the pot pins. Phew and doh!

Leg 2 IC1 to R8, R8 to pin 3 pot both have continuity. I will take the board out and check the pot to C5. C5 confirmed as correct value.

The bass roll off Is too effective. It is as rolled off as the circuit will allow, like it’s stuck CCW resulting in a too bright sound with nasally mids. It should sound pretty good once more bass returns.

Check continuity from pins 1+2 of the pot to one leg of the 2.2u cap, then the other leg to ground. Also verify value of cap and that it’s in the correct orientation.

 

[Noodles]

Continuity is correct as noted above. I have verified the value as it is written on the cap, but not sure how to measure it with my DMM…web search to follow. In the Aion build, it is non polarized (differs from the PedalPCB build).

 

[DailyDovetails]

Maybe check R7 and C4 also. They are a low pass filter as well.

 

[music6000]

Check the Resistors on the PCB, sounds like it could be an incorrect value???
R8 - 1K5 - Brown, Green, Black, Brown, Brown
R7 - 820 Ohms - Grey, Red, Black, Black, Brown

 

[Noodles]

Check the Resistors on the PCB, sounds like it could be an incorrect value???
R8 - 1K5 - Brown, Green, Black, Brown, Brown
R7 - 820 Ohms - Grey, Red, Black, Black, Brown

I think we may have a winner. Looks like I did 1.5M for R8. I’ll replace that with the correct value. Again…doh!

 

[Noodles]

Yeah, that worked. Embarrassed at missing that. I’ve got a meatier one coming soon that is more complex, but I’m going to check all the values first .

Question for my education…if I’m not mistaken, the resistors adjacent to the Bass pot are there to resist bass frequencies to ground. So, considering that I had a higher value resistor in there, why did the pedal not have more bass?

 

[Feral Feline]

...

Question for my education…if I’m not mistaken, the resistors adjacent to the Bass pot are there to resist bass frequencies to ground. So, considering that I had a higher value resistor in there, why did the pedal not have more bass?

Somebody can correct me if I'm mistaken, the R8/C5 cap-combo is bleeding highs to ground. The more you bleed highs to ground, the more bassy your circuit sounds. Further, R8&C5 are working in parallel to R7&C4, the latter providing a fixed tone-sculpting but it was the only tone sculpting going on since R8 was 1M5 and it wasn't letting any signal through to the pot, forcing R7&C4 to do all the tone-shaping.

Once you changed R8's 1M5 to 1k5, signal was finally able to flow through the BASS-pot and C5, taking some of the signal-shaping duties away from R7&C4.


At 1M5, R8 was just one big dam.

Dam it! DAMN IT ALL TO HELL!

 

[music6000]

I think we may have a winner. Looks like I did 1.5M for R8. I’ll replace that with the correct value. Again…doh!

I't's good practice to check Resistor values around the problem area first.
If I got a dime for every time I have spotted or heard a wrong resistor value on this Forum, It's always that 4th Band that catches Members out!
Glad it was a good end result.
Here is the Resistor Value Calculator that I recommend
Click on Bands for 5 colors:

Resistor Calculator

Resistor Calculator is an App developed by CherryJourney to help the user find the value of a resistor.

resistor.cherryjourney.pt

 

[Feral Feline]

Yup, always good to double check resistors as you pop a board, 'cause you never know when a resistor is a dud or perhaps got mistakenly put back in the wrong container after a spill or breadboarding session or whatever.

I use the Digikey resistor band calculator:

https://www.digikey.ca/en/resources/conversion-calculators/conversion-calculator-resistor-color-code

 

[DailyDovetails]

For what it’s worth I always check all the Caps and resistors with a meter before installing them. It takes a little more time upfront but it’s way faster than finding the one you messed up on. Also I occasionally have a resistor which is either not the marked value or measures as open.

 

[music6000]

For what it’s worth I always check all the Caps and resistors with a meter before installing them. It takes a little more time upfront but it’s way faster than finding the one you messed up on. Also I occasionally have a resistor which is either not the marked value or measures as open.

I do the same thing & my resistors are all in sealed packets with the value on it from the shop & I just cut each individually & push them out one at a time!

 

[DailyDovetails]

I do the same thing & my resistors are all in sealed packets with the value on it from the shop & I just cut each individually & push them out one at a time!

Similarly mine are in marked bags and in card sleeves in a binder organized by value.

 

[Noodles]

For what it’s worth I always check all the Caps and resistors with a meter before installing them. It takes a little more time upfront but it’s way faster than finding the one you messed up on. Also I occasionally have a resistor which is either not the marked value or measures as open.

Good idea. I think that is part of the problem with the other pedal I built that is only partially working.