Aion Theseus - KOT Clone Troubleshooting

[davidplaysbass]

Greetings all! New to the forum and still a novice pedal builder after several projects built from kits or at least PCB/plans and would love some assistance troubleshooting to see where I went wrong as a knuckle-dragger with a soldering iron. I read the DEBUGGING pinned post so here's the results from the process I found there:

1. What does it do, not do, and sound like? Left/red/B side is perfect. Right/blue/A side makes almost no sound when engaged (bypasses as expected). If I crank up the gain on my amp or interface I can hear a faint pop with the transients of each note but that's it. With a little extra or cranking the left/red/B side at the same time, I can hear a bit of the note sustained but it's barely perceptible and it's crackly and distorted like an old, blown amp. I've checked/reflowed every solder joint, tried every combination on the dip switches & knobs, cleaned the flux from the board and nothing helps. I've tried searching online but everything I find seems to lead to the usual questions about static discharge pops when engaging the switch.

2. Name of the circuit = Theseus by Aion FX (King of Tone clone) full kit (all parts and components included)

3. Source of the circuit = Product page: https://aionfx.com/project/theseus-dual-overdrive - Build documentation including schematic: https://aionfx.com/app/files/docs/theseus_kit_documentation.pdf

4. Any modifications to the circuit? No

5. Any parts substitutions? No

6. Positive ground to negative ground conversion? No

7. Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => No battery or clip. Using relatively new Truetone 1 Spot DC wall wart for testing. I've tested it on a number of working pedals (commercially built as well as projects) with zero problems since encountering the issue with this build. I've also tested with the power supply on my board with identical results.

Now insert the battery into the clip (plugged in). If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:

Voltage at the circuit board end of the red battery lead = 9.41V
Voltage at the circuit board end of the black battery lead = 0.00V

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Both 3-position DIP switches have each switch turned off (clean boost mode on both sides) and all pots at 100%.

IC1 (non-working side) JRC4580D
P1 1.33V
P2 0.35V
P3 2.34V
P4 0.00V
P5 4.40V
P6 4.74V
P7 4.48V
P8 8.99V

IC2 (working side) JRC4580D
P1 4.47V
P2 4.72V
P3 4.40V
P4 0.00V
P5 2.27V
P6 4.57V
P7 4.58V
P8 8.99V

D1 (footswitch PCB) 1N5817
A (anode, the non-band end) = 9.41
K (cathode, the banded end) = 9.21

D2 (non-working side) BAS33
A = 4.69
K = 4.14

D3 (non-working side) BAS33
A = 4.14
K = 3.58

D4 (non-working side) BAS33
A = 3.58
K = 3.03

D5 (non-working side) BAS33
A = 3.03
K = 4.71

D6 (non-working side) 1N914
A = 4.47
K = 4.14

D7 (non-working side) 1N914
A = 4.12
K = 4.47

D8 (working side) BAS33
A = 4.68
K = 4.12

D9 (working side) BAS33
A = 4.12
K = 3.57

D10 (working side) BAS33
A = 3.57
K = 3.02

D11 (working side) BAS33
A = 3.02
K = 4.69

D12 (working side) 1N914
A = 4.47
K = 4.14

D13 (working side) 1N914
A = 4.13
K = 4.47



I hope this is up to snuff but please let me know if I should provide any other info or adjust my methods. Really hope it's a relatively simple thing to fix. Thank you in advance for any help you're able to give!

[davidplaysbass]

Sorry, updated a couple of the readings because they looked questionable when I re-read the post so I checked them again.

[tootsMcgee]

Interesting, IC1's "first half" (pins 1-3) are at a much lower voltage than expected. It should be around 4.5V on those pins. Pin 3 is receiving 4.5V from VB via R1, a 1M resistor.

Can you check the voltage relative to ground at these points?

R1 both sides
R27 both sides
R12 both sides

The idea is that your power supply gets filtered and passes into two parallel stages to divide your 9V down to 4.5V, the midpoint for the opamps to operate at to have the widest possible headroom available between 0V and 9V. This is R27/R12/R13 for IC1 and R28/R25/r26 for IC2.

If the midpoint is, say, down near 1-2 or 0V, then the opamp can properly amplify positive signal swing all the way up to 9V, but negative signal swing will hit the 0V ground rail sooner and get clipped something ugly. So that would be why it sounds so distorted.

[antonis]

Just check R1 proper connection..

The other side of IC1 is biased fine (healthy VB presence), so no need to check R27/C21 & R12/R13/C10..

edit: Both ICs non-inverting inputs voltages seem fine (low voltage to those biased via resistor is due to moderate to low DMM impedance) so check IC1A feedback loop..

[ElectricDruid]

Both ICs non-inverting inputs voltages seem fine (low voltage to those biased via resistor is due to moderate to low DMM impedance) so check IC1A feedback loop..

+1 agree. It's that pin 1 output and pin 2 -ve input that really look wrong. Something is not right amongst those parts Antonis highlighted.

[duck_arse]

allow me to say - welcome to the forum. I'm just saying that so I can also say - we ALWAYS like to see what you have built. we like to look at solder joints and resistor colour bands [or red with white numbers] and jack wiring and IC's in sockets and backwards transistors ..... well, we don't actually, but that's the rules. always post photos.

IC1 (non-working side) JRC4580D
P1 1.33V
P2 0.35V
P3 2.34V
P4 0.00V
P5 4.40V
P6 4.74V
P7 4.48V
P8 8.99V

IC2 (working side) JRC4580D
P1 4.47V
P2 4.72V
P3 4.40V
P4 0.00V
P5 2.27V
P6 4.57V
P7 4.58V
P8 8.99V

this is how we do it. compare working against not working, see what's different. and in this case, both halves are the same parts/values [aren't they?] so you have no excuses.

[davidplaysbass]

Interesting, IC1's "first half" (pins 1-3) are at a much lower voltage than expected. It should be around 4.5V on those pins. Pin 3 is receiving 4.5V from VB via R1, a 1M resistor.

Can you check the voltage relative to ground at these points?

R1 both sides
R27 both sides
R12 both sides

The idea is that your power supply gets filtered and passes into two parallel stages to divide your 9V down to 4.5V, the midpoint for the opamps to operate at to have the widest possible headroom available between 0V and 9V. This is R27/R12/R13 for IC1 and R28/R25/r26 for IC2.

If the midpoint is, say, down near 1-2 or 0V, then the opamp can properly amplify positive signal swing all the way up to 9V, but negative signal swing will hit the 0V ground rail sooner and get clipped something ugly. So that would be why it sounds so distorted.

Just check R1 proper connection..

The other side of IC1 is biased fine (healthy VB presence), so no need to check R27/C21 & R12/R13/C10..

edit: Both ICs non-inverting inputs voltages seem fine (low voltage to those biased via resistor is due to moderate to low DMM impedance) so check IC1A feedback loop..

Both ICs non-inverting inputs voltages seem fine (low voltage to those biased via resistor is due to moderate to low DMM impedance) so check IC1A feedback loop..

+1 agree. It's that pin 1 output and pin 2 -ve input that really look wrong. Something is not right amongst those parts Antonis highlighted.

Checking all of these now! Thanks, friends!

allow me to say - welcome to the forum. I'm just saying that so I can also say - we ALWAYS like to see what you have built. we like to look at solder joints and resistor colour bands [or red with white numbers] and jack wiring and IC's in sockets and backwards transistors ..... well, we don't actually, but that's the rules. always post photos.
<...>
this is how we do it. compare working against not working, see what's different. and in this case, both halves are the same parts/values [aren't they?] so you have no excuses.

Thanks for the welcome and completely understand! I'll see what I can get going on that front. Yes, both sides are/should be identical but, other than doublechecking component values and solder joints, I get lost in deeper dives for troubleshooting...

Will post additional measurements and photos shortly!

[ElectricDruid]

Also a belated thanks for *actually reading* the debugging thread and bonus points for *understanding it* as well! It's nice to get someone who has bothered to provide all the information needed, especially voltages and the correct schematic. Much appreciated.

The number of times people show up with a two sentence message that says something like "My BootiqBuild Raging Rocket pedal kit isn't working. What should I try next?"...after the first few dozen times, it starts to get taxing to be polite, lol

[antonis]

Also a belated thanks for *actually reading* the debugging thread and bonus points for *understanding it* as well! It's nice to get someone who has bothered to provide all the information needed, especially voltages and the correct schematic. Much appreciated.

+1000..!!

Also a belated Welcome..

[davidplaysbass]

@tootsMcgee
R1 1M
4.40V
2.33V

R27 47k
8.99V
9.21V

R12 47R
8.98V
4.39V


@antonis & @ElectricDruid
R2 100k
1.21V
1.21V seems suspect but not sure if I need to replace the resistor or if it's something else...

R3 1k
1.21V
1.21V same as above

R4 27k
1.18V
1.21V

R5 33k
1.18V
1.21V


@duck_arse
Solder side of I/O & footswitch boards:


Solder side of main board:


Component side of footswitch board:


Component side of I/O board (no idea why that would be needed but throwing it in for good measure  ):


Component side of non-working channel on main board:


Component side of working channel on main board:

[davidplaysbass]

Oh! Meant to also say I'm not sure if I should go so far as to desolder C2 & C3 to measure since those are in @antonis' image as well but let me know if you think it would help.

Appreciate the kind words, all. I've done more than my fair share of troubleshooting for myself and others in person, over the phone, and on the interwebz so I fully understand your plight and appreciate your efforts and willingness all the more for it!

[antonis]

Neither C2 nor C3 could be involved in DC misbias..

i.e.
For C2 shorted, IC1A turns into a buffer (voltage follower)..
For C2 open, NFB LPF is deleted..

For C3 shorted, R5 left leg is directly connected to R4 left leg (no big deal as long as C4 is there and OK(*)..)
For C3 open, R5 is out of game (absolutely no big deal..)

(*) For C4 shorted, IC1A pin in should permanently hit positive power rail (DC gain same as AC gain)..
    For C4 open, same as what happens for C2 shorted (for different reason but with same result)..

Conclusion: Check for only resistors/pot proper connections..

[davidplaysbass]

Just checked all 6 pots and all seem to be working measured both on the leads and the copper of the board to ensure they're connected properly. Also checked the counterparts to R2 & R3 that I expressed concern over (R15 & R16) and while they both measured different voltages than the ones I originally checked (not sure why), they're both the same on both sides of the resistor as well. I don't understand how that works but at least it gives me a better feeling that R2 & R3 are ok. Or is that a worse feeling because I still have no idea where the problem is...?   

[tootsMcgee]

Could IC1 be bad? You don't happen to have a spare?

Can you swap the two ICs? They're identical. If the problem follows them we know that IC1 is bad.

If you don't have a chip puller, take it slow with prying it out, and go a little bit at a time. It's easy to mess up the leads. Replacements are cheap but it's annoying having to wait.

EDIT: I don't see anything obvious wrong with the board but I always suggest cleaning the back with some isopropyl alcohol and a toothbrush if you've got some handy. It makes it easier to spot issues. It'll take a couple of passes. Let the first one sit a bit to dissolve the flux and then brush it away, then add more, etc. Otherwise it just spreads the flux around.

[davidplaysbass]

Could IC1 be bad? You don't happen to have a spare?

Can you swap the two ICs? They're identical. If the problem follows them we know that IC1 is bad.

If you don't have a chip puller, take it slow with prying it out, and go a little bit at a time. It's easy to mess up the leads. Replacements are cheap but it's annoying having to wait.

EDIT: I don't see anything obvious wrong with the board but I always suggest cleaning the back with some isopropyl alcohol and a toothbrush if you've got some handy. It makes it easier to spot issues. It'll take a couple of passes. Let the first one sit a bit to dissolve the flux and then brush it away, then add more, etc. Otherwise it just spreads the flux around.

I tried swapping the ICs early on...    Stays consistent per channel, doesn't follow the chip. I did a single pass with the IPA. Guess I'll grab an IPA and apply additional IPA. 

[antonis]

Take IC1 out of socket and measure voltages on pins 1,2 & 3..

You should get previous VB measurement on pin 3 and nothing on pins 2 & 1..

[ElectricDruid]

Some of these joints look like they need reheating to me. They're "lumpy" rather than smooth and shiny. That indicates to me that you probably didn't get enough heat on them. Hold the soldering iron on the joint until you see the solder "flow". On an empty joint on a PCB with plated through-holes like this, you usually see it get "sucked" into the hole as soon it gets to the right temperature too. You might see that on some of these if they really weren't heated enough. The pad warms up first and the solder sticks to the pad, but it hasn't warmed up the component leg or the through hole enough for it to flow into all the spaces.

[duck_arse]

Also checked the counterparts to R2 & R3 that I expressed concern over (R15 & R16) and while they both measured different voltages than the ones I originally checked (not sure why), they're both the same on both sides of the resistor as well.

I'm not sure I'm following this bit. you should test the parts end to end for value/voltages, and if dicky, the test from one component to where it connects, so you then discount broken tracks and the like. if you follow.

geeze they are big photos. we can't complain about them.

what's happened to the inner leg/pad of R5, especially solder side?


it might be a lighting trick, but is the red led in this pic flat-backwards?

[davidplaysbass]

Take IC1 out of socket and measure voltages on pins 1,2 & 3..

You should get previous VB measurement on pin 3 and nothing on pins 2 & 1..

Sorry, I'm a bit confused about this process. If I take the IC out, there won't be any voltage to measure, will there? Am I misunderstanding?

Some of these joints look like they need reheating to me. They're "lumpy" rather than smooth and shiny. That indicates to me that you probably didn't get enough heat on them. Hold the soldering iron on the joint until you see the solder "flow". On an empty joint on a PCB with plated through-holes like this, you usually see it get "sucked" into the hole as soon it gets to the right temperature too. You might see that on some of these if they really weren't heated enough. The pad warms up first and the solder sticks to the pad, but it hasn't warmed up the component leg or the through hole enough for it to flow into all the spaces.

I've reflowed every joint at least once but I'll give the non-working side another solid pass later today.

I'm not sure I'm following this bit. you should test the parts end to end for value/voltages, and if dicky, the test from one component to where it connects, so you then discount broken tracks and the like. if you follow.

Sorry for the confusion! If I understand correctly, the voltage measured from ground to one end vs from ground to the other should be different, no? Is that not the function of the resistor here?

geeze they are big photos. we can't complain about them.

lol yeah...sorry...?    Too many tiny pics in various other threads on other forums so I figured I'd maximize!

what's happened to the inner leg/pad of R5, especially solder side?

Hahahah I was hoping nobody would notice that. I think I stood a little too close when I clipped the lead on that one... Fortunately, there's still just enough length that it comes all the way through the hole, seems to make contact with the board, and holds solder. Is there an easy way to check to see if that's the issue short of replacing the component?

it might be a lighting trick, but is the red led in this pic flat-backwards?

You're seeing that right! It's a quirk of Kevin's component sourcing and covered in the build documentation at the bottom of page 22: https://aionfx.com/app/files/docs/theseus_kit_documentation.pdf

[tootsMcgee]

About the IC: If you take out the chip, it won't conduct or function, so pins 1 and 2 of IC1 should have no voltage on them. The only connection to something that can provide DC current would be IC1 itself, including the second half of IC1 which would be not connected, and would be blocked by C5 even if it was connected.

So in theory, you should be able to see the low ish ~2 volts on pin 3, and there should be nothing on 2 and 1. If there's something on either of those pins then there's a short somewhere. I think.

Good call antonis on the lower voltage on the first stage of each half; I always forget about DMM impedance. Basically the multimeter draws more current to "sample" it than the 1M resistor to VB/VD can keep up with, so it shows up as a voltage drop. The second stage of each half doesn't have this issue because it's connected directly to the power rail.

I'm sure there's an exception somewhere but in general you can test circuits without ICs installed just fine, it just won't work. It can be a good way to make sure you're getting expected power rail voltages on pins 4 and 8 for most dual-op amps, or testing voltages that you would be sending to more expensive chips before installation You don't want to fry BBDs...

Edit: Look very carefully under the socket from the top side to double check that nothing is shorting...I'm running out of ideas...

Edit 2: Is there any way he can test the resistors in place in case something is mis-marked?