Aion Refractor Klon Klone issues - Treble pot not working

[brusinow]

Hey all,

I built a Klon Klone with the Aion Refractor board a few months back. I built to Silver Pony specs originally (except for C13 which was the standard 820pF value) and it worked well and as expected based on youtube video samples. I finally got around today to trying a lower value (560pF) for that C13 cap, and after the mod I no longer have any functionality from the treble pot. When testing with the gain all the way down, the high end comes through more as I turn up the volume pot, but compared to the bypassed pedal there is a lot of high end loss. As soon as the gain comes in, that high end from the clean circuit get's even less present. I verified that the resistance values from the pot are still as expected and I took IC voltages for reference (about 12:00 on all pots):
IC1 (TL072)
1= 4.69    5= 4.68
2= 4.69    6= 4.7
3= 3.60    7= 4.72
4= 0         8= 9.4

IC2 (TL072)
1= 4.71    5= 4.67
2= 4.69    6= 4.69
3= 4.69    7= 4.68
4= -8.67   8= 16.71

IC3 (TC1044SCPA)
1= 9.39    5= -8.67
2= 4.84    6= 4.59
3= 0         7= 6.1
4= -4.24   8=9.4

Any help/suggestions would be much appreciated - this is a heck of a circuit to debug!

Thanks,
Brent

[DIY Bass]

You may need to explain what is going on a bit more.  What I got was:

I had a circuit that I liked.
I made a mod.
Now I don't like it.

To which the obvious reply is "reverse the mod then"

I would assume you must have thought of that though.

[brusinow]

Um, ok...

The reason I'm asking this is because the high pass part of the circuit is after (and seemingly unrelated) to the change in capacitor at the signal summing stage a step earlier. Reducing the value of this cap would let more high end through and should not affect the functionality of this treble pot.

It is not that I "don't like" the mod - it's that something unrelated seems to have gone wrong in the process.

[Slowpoke101]

If you put the original capacitor back into the circuit does the circuit behave as it did before you changed the capacitor ?
If it does go back to original then the newer capacitor may be suspect, if it doesn't and you are still missing 'highs' then something has been damaged.

[brusinow]

Ok, so I put sockets into C13 and replaced the original capacitor - still have a non-responsive treble pot. Based on the circuit analysis at ElectroSmash(https://www.electrosmash.com/klon-centaur-analysis), this C13 cap along with the R20 resistor form the low-pass filter that shapes the merged clean and driven signals being merged in the first half of IC2 before heading to the second half where the high-pass filter connected to the treble pot is applied. I double checked the voltage readings from my IC's and they still look like the numbers I referenced in my first post.

The pedal is currently functioning as if there were no treble pot, but otherwise sounds really good.

If anyone has any Klon circuit-specific suggestions regarding what might be at fault, I'd really appreciate it!

Thanks for the suggestions so far,
Brent

[Slowpoke101]

Since the fault is still present with the original capacitor re-installed the most likely problem is a connectivity issue.
Using your multimeter on continuity test (or low ohms), remove power from the effect and test if the following components are connected.
One leg of C13 to one leg R21.
The other leg of C13 to one leg of R20.
Repair any open circuits found.
Removal of C13 may have caused some damage to the board and caused a break in a circuit track.

[DIY Bass]

It is also possible that you may have accidentally made a solder bridge or cold joint when I was shifting out C13.  I know I have accidentally heated joints near where I was working in the past.  A quick check suggests R16, R17, R19, R4 and C12.  A lot of that network is supposed to be joined, but quickly check to make sure it all connects as it should and reflow any dodgy looking joints.

[brusinow]

Thanks guys, initial testing found no connection between C13 and R21 - will repair that trace and see what I find.

Good suggestions about that bunch of resistors near C13 - I'll double check that I didn't get any solder in there.

Brent

[PRR]

The most likely cause of NO action would be bad joint on C14 or RV2.

[brusinow]

Hey all, made the fix from C13 to R21, confirmed continuity with multimeter, and verified connectivity all the way through IC2 - now I'm getting little to no sound. I ordered a new Aion board just in case - this was the second pedal ever that I built and I admittedly was still getting my soldering in order (which made the desoldering more difficult).

I'll check around C14 and RV2 and see if I'm missing something.

Thanks again for all the help - this is a really cool community here.

Brent

[Slowpoke101]

That is disappointing. Keep on looking for any mistakes you may have made.
The image below show the connection points between C13 and R21 that I suggested that may have been open circuit.



Just double check that it was these two points that you connected together.

[brusinow]

 

I totally soldered to the other side of C13 (cue embarrassed laugh).

Slowpoke101, thanks for the graphic (and for not overestimating my ability to figure some basic stuff out).

Will adjust and report back.
Brent

[brusinow]

That did it! Working like a charm now - going to put it back in the box and get back to playing.

Thanks again for all the help!

[Slowpoke101]

Success! 
It is a good feeling to have been able to repair your own gear.