Aion Cerulean (Bluesbreaker/Morning Glory) Kit - No clipping

[jabbowookie]

Just finished the Aion Cerulean kit and I'm having an odd issue. The clipping section/switches are doing nothing. Volume, gain, and tone all work, but I'm getting what sounds like IC distortion only. The soft and hard clipping sections don't seem to be working.

I measured voltages at the IC and all normal.
I tried a different IC, no change.
I'm getting 4.5V on the middle pin of each switch.
I checked continuity on each switch, all good.
I reflowed as many solder joints as I could.

Posting the schematic below, what would cause both clipping sections to not work? Is there a specific section/components I should check? As cliche as it is, I've built hundreds of pedals and quite a few Aion projects and kits, and I've never had an issue quite like this one.

Any help would be appreciated!

[11-90-an]

Give us voltages plez IC and JFET... also pictures, front and back

can you check R5 and R6 values?

[jabbowookie]

TL072
1 4.45V
2 4.67V
3 4.37V
4 0
5 2.22V
6 4.46V
7 4.46V
8 8.93V

2N5457
Drain 3.39V
Gate 2.96V
Source 0V

R5: 220K
R6: 6K8

[11-90-an]

first thing I noticed is TL072 pin 8. It should be at about 9v...

can you check if it's secure in it's socket? also check pin 8 solder joint.

[jabbowookie]

first thing I noticed is TL072 pin 8. It should be at about 9v...

can you check if it's secure in it's socket? also check pin 8 solder joint.

I had the pin numbers reversed in my voltages above. Should look right now.

[antonis]

So, does now clip or not..??

[jabbowookie]

So, does now clip or not..??

No, still doesn't clip. I was just telling 11-90-an that I had the IC pin numbers mixed up when I gave him my voltages, so I fixed them in the post above.

[Steben]

Switch? Did you check the nodes / shorts when switching?

[jabbowookie]

Switch? Did you check the nodes / shorts when switching?

Yep. All poles have continuity. First thing I checked.

[Vivek]

Do you have access to an Oscilloscope ?

[jabbowookie]

Do you have access to an Oscilloscope ?

I do not.

[Vivek]

I will hazard a guess.

If there is no change in sound while switching the diodes in the feedback loop

It might mean that the signal at that point is too high

and already a square wave even before the diodes chop them into square waves of a different size.

which might mean that gain of the first stage is too high and first IC is saturating rail to rail and producing square waves.

Then I would check the values of Drive pot, R3 and R2.

[jabbowookie]

I will hazard a guess.

If there is no change in sound while switching the diodes in the feedback loop

It might mean that the signal at that point is too high

and already a square wave even before the diodes chop them into square waves of a different size.

which might mean that gain of the first stage is too high and first IC is saturating rail to rail and producing square waves.

Then I would check the values of Drive pot, R3 and R2.

Drive is B100K, and R3 - 4k7, R2 - 3k3 as called for in the schematic.

I think there's something going on in the hard clipping section. I'm using a signal probe and I'm not getting any sound from the middle pole of the hard clipping switch, and faint garbled sounds from the outer poles when the switch is in the up or down. I get clear sound from the middle pole of the soft clipping switch, as well as the other two poles depending on position.

[antonis]

I don't feel sympathy for designs which use AC ground (VR) instead of circuit ground for just saving a DC blocking cap..

[Steben]

I will hazard a guess.

If there is no change in sound while switching the diodes in the feedback loop

It might mean that the signal at that point is too high

and already a square wave even before the diodes chop them into square waves of a different size.

which might mean that gain of the first stage is too high and first IC is saturating rail to rail and producing square waves.

Then I would check the values of Drive pot, R3 and R2.

Drive is B100K, and R3 - 4k7, R2 - 3k3 as called for in the schematic.

I think there's something going on in the hard clipping section. I'm using a signal probe and I'm not getting any sound from the middle pole of the hard clipping switch, and faint garbled sounds from the outer poles when the switch is in the up or down. I get clear sound from the middle pole of the soft clipping switch, as well as the other two poles depending on position.

questions:
- do you get a volume boost with the soft switch in middle?
IF SO : soft clippers probably do work
- do you get louder volume with soft clipping in outer pos compared to hard clipping in outer pos?
IF SO : hard clippers probably do work

I just noticed you cannot check truely the first question if the middle pos of the hard switch is faulty 

[jabbowookie]

I will hazard a guess.

If there is no change in sound while switching the diodes in the feedback loop

It might mean that the signal at that point is too high

and already a square wave even before the diodes chop them into square waves of a different size.

which might mean that gain of the first stage is too high and first IC is saturating rail to rail and producing square waves.

Then I would check the values of Drive pot, R3 and R2.

Drive is B100K, and R3 - 4k7, R2 - 3k3 as called for in the schematic.

I think there's something going on in the hard clipping section. I'm using a signal probe and I'm not getting any sound from the middle pole of the hard clipping switch, and faint garbled sounds from the outer poles when the switch is in the up or down. I get clear sound from the middle pole of the soft clipping switch, as well as the other two poles depending on position.

questions:
- do you get a volume boost with the soft switch in middle?
IF SO : soft clippers probably do work
- do you get louder volume with soft clipping in outer pos compared to hard clipping in outer pos?
IF SO : hard clippers probably do work

The only sound I get is what sounds like IC distortion only. Nothing happens when I flip through either clipping switches. Volume, gain, and tone pots all work but it sounds splatty and terrible.

[Steben]

Perhaps Try checking every VR node is in fact 1/2V, but that can't be if the PCB is correct.
node 5 of the opamp should not be that low!

[jabbowookie]

Perhaps Try checking every VR node is in fact 1/2V, but that can't be if the PCB is correct.
node 5 of the opamp should not be that low!

It's kinda strange I'm having the same issues as this guy. See reply #11. He never replied so I'm curious what was his issue was. My IC readings are in line with his.

https://www.diystompboxes.com/smfforum/index.php?topic=121501.0

I found another thread he started at TDPRI

https://www.tdpri.com/threads/aion-cerulean-kit-bluesbreaker-help.902611/

[Vivek]

Looks like it will be worth it to contact Aion, they are helpful

Else, you can check the PCB to make sure it successfully follows the schematic

[jabbowookie]

It was a bum transistor in the recovery stage. The transistor was so bad I couldn't hear any changes in the clipping. All is working as it should.