Help with Aion Theseus (KOT clone)

[neiltheseal]

You have been really helpful and helped me fix the last two pedals that I have had problems with.

Well here I am with a third! I recently put together a Theseus from Aion FX (a king of tone clone) and I have managed to get half of it working and sounding great, but only side b.

Pics of both sides of the PCB are below. Side B works perfectly (except for the the LED not working) but Side A does not (the side with no LED).

https://imgur.com/gallery/TzwWjoG

I did an audio probe and I get a signal on the input of the PCB, one leg of the RPD 1 and one leg of C1. No where else in the circuit. I assume that the signal should be present on both pins of C1 and this is probably the issue. If I re solder C1 and/or replace it with a new one then I should get a signal further into the circuit right?

The build docs are below (schematic on page 7).

https://aionfx.com/app/files/docs/theseus_documentation.pdf

Thanks in advance!

[mauman]

Welcome back!  Thanks for all the resources (pics, schematic, good description of what you've done so far.)  Given all that:

1. Verify that the back of the TONEA pot isn't touching the IC1 pins underneath it.  Best to insulate the back of both TONE pots like you did VOL and DRIVE pots, or with a piece of tape.  BTW, VOL and DRIVE pots aren't as important to insulate, they can't touch the PCB solder side.

2. Remove IC1 from the socket, apply power and signal to input of side A.  Trace signal from input to IC1 socket pin 3.  Good signal there? 

2.A. If yes, replace IC1 and try again, the IC is faulty. 

2.B. If no, the trouble is between C1, R1 and IC1 pin 3.  Checking for signal after each step:  Check the value of R1 - could it be 1k instead of 1Meg?  Resolder both sides of C1. Visually check for shorts between C1/R1/IC1 pins and any other nearby pins.  Resolder IC1 pin 3.  With no power applied, check continuity between C1 (the side that had no signal before) and IC1 pin 3.    Replace C1.  Then let us know.

[neiltheseal]

Welcome back!  Thanks for all the resources (pics, schematic, good description of what you've done so far.)  Given all that:

1. Verify that the back of the TONEA pot isn't touching the IC1 pins underneath it.  Best to insulate the back of both TONE pots like you did VOL and DRIVE pots, or with a piece of tape.  BTW, VOL and DRIVE pots aren't as important to insulate, they can't touch the PCB solder side.

2. Remove IC1 from the socket, apply power and signal to input of side A.  Trace signal from input to IC1 socket pin 3.  Good signal there? 

2.A. If yes, replace IC1 and try again, the IC is faulty. 

2.B. If no, the trouble is between C1, R1 and IC1 pin 3.  Checking for signal after each step:  Check the value of R1 - could it be 1k instead of 1Meg?  Resolder both sides of C1. Visually check for shorts between C1/R1/IC1 pins and any other nearby pins.  Resolder IC1 pin 3.  With no power applied, check continuity between C1 (the side that had no signal before) and IC1 pin 3.    Replace C1.  Then let us know.

Thanks for your response. Just got back from a trip and have had a look at this.

I put a cover on the tone pot.

I tried re soldering C1 and R1 but I may have removed the metal ring on the pcb connecting C1. Now with an audio probe I get no signal from C1 and R1...

However now the pedal works although with lots of hissing and it is very quiet. So some progress but I am baffled. there is signal on all pots including the presence trimpot. In fact all pots work correctly, the signal is just barely audible and sounds like white noise over the guitar.

I took the IC out and tested signal for leg 3 (and all) and there is absolutely no signal. I swapped the IC and the problem persists so it's not an IC problem but elsewhere. I can get a faint signal through the whole circuit except C1 and R1, through  all of the diodes except D2 and d5 and out of pins 1, 2 and 7 of the IC.

Do you have any pointers where I should look now?

[mauman]

I think you're now on step 2.B. above.  I'd replace C1.  The problem is still right there around C1/R1/IC1 pin 3. Either C1 is faulty, or R1 is the wrong value, or there's a problem with the trace from C1/R1/IC1 pin 3, or there's a short to ground on that path...

[neiltheseal]

Thanks. I tried removing c1 but the metal circle on the pcb came off. Does this mean it's stuffed?

I'll remove it completely tomorrow and replace with a new one.

[mauman]

You can check continuity between each C1 hole and the other components.  Easiest to do before you reinstall C1.  Check both the front and back side of the PCB, you may have lost continuity on one side and still be OK the other.

One side of C1 (one of the holes) should show a short (less than 1 ohm) to the PCB Input hole and one end of RPD.  The other side of C1 should show a short to IC1 pin 3 and to one side of R1.  Again, check these connections on both sides of the PCB.  If they're all good, just replace C1.

If any of these connections is missing now, you can run a short jumper to replace it from the proper leg of C1 to the leg of RPD or R1.  If a connection is missing on the component side, run the jumper on the component side while you're replacing C1 (attach the jumper to C1 before you install it.)  If it's the solder side, run the jumper on the solder side by leaving a C1 leg a little long so you can attach a jumper, or just bend the long leg of C1 to the correct point, solder it and clip the excess.   

[neiltheseal]

You can check continuity between each C1 hole and the other components.  Easiest to do before you reinstall C1.  Check both the front and back side of the PCB, you may have lost continuity on one side and still be OK the other.

One side of C1 (one of the holes) should show a short (less than 1 ohm) to the PCB Input hole and one end of RPD.  The other side of C1 should show a short to IC1 pin 3 and to one side of R1.  Again, check these connections on both sides of the PCB.  If they're all good, just replace C1.

If any of these connections is missing now, you can run a short jumper to replace it from the proper leg of C1 to the leg of RPD or R1.  If a connection is missing on the component side, run the jumper on the component side while you're replacing C1 (attach the jumper to C1 before you install it.)  If it's the solder side, run the jumper on the solder side by leaving a C1 leg a little long so you can attach a jumper, or just bend the long leg of C1 to the correct point, solder it and clip the excess.

You are the best!

Replaced C1 and used your jumper suggestion and it works perfectly! Thanks so much.