Aion Refractor problem

[Simmul8]

I've built circuits and effects pedals before, and at risk of sounding modest had no idea that it would be the Aion Refractor that would stump me. I've double then triple checked the component values and placements. I've checked my pin voltages and they are all correct according to previous Refractor posts. I also have touched up every solder joint with some more solder just in case.
My is basically in the gain pot. I am getting an amplified signal when it's on yet not "gainy" or Centaur sounding. Basically just a clean boost. Volume and tone both work fine but when I turn the gain know I go from 0 gain to the same 0 gain with a swooshing sound in between. (Yes, I have taken the gain pot off and measured the resistance. 0-100k one way. And 100k-0 the other. On both gangs)(no the pot isn't shorting out on the rear of the circuit. The brown stuff on the solder joints is just flux. Its never been a problem in about 20 other circuits I've designed and built.)
photos are here http://imgur.com/gallery/Nf5ci/new
Build information is here https://aionelectronics.com/project/refractor-centaur-overdrive/

[jez79]

Are you also using the little 3pdt switch board along with the main circuit board?
The input and output of the circuit board are shared between big and small board.
Maybe you're tapping an output before the actual end of the circuit?

[Simmul8]

Hi thanks for your reply. I am using the daughterboard and it looks like I've wired it all exactly as the wiring diagrams show.

[Frank_NH]

I've built the Aion Refractor (used the earlier PCB) and it is the one pedal that I use at EVERY gig.  I use it as a low gain preamp because it makes my guitar signal sound so good in conjunction with my other pedals.  The gain is definitely there though if you turn it up.

I read your description and looked at the schematic - here's what I'd check:

* Check C8.  See if there is a short across this cap with your DMM.  If C8 was shorted, the op amp would not provide any gain.
* If C8 is OK, check the op amp itself (i.e. replace IC1 with another TL072).  Check your IC voltages too and make sure they look reasonable.

Hope this helps.  Good luck - it's definitely worth getting this one working! 

[Benoi31]

I have just made one ( http://www.coda-effects.com/2015/09/klon-centaur-clone-and-mods-aion.html ) very cool pedal indeed !

Have you tried to audioprobe it ? It can really help to decipher what the problem is sometimes.

[Simmul8]

Thanks Frank, I will double check that capacitor for sure.
Benoi, I saw your build report on Aion's website. Nice looking finish, good job. Might try to audio probe

[Simmul8]

Still no luck unfortunately. C8 is fine. Replaced it with an equal value ceramic and the same problem is occurring. I am starting to think whether it's possible I have a bad board. There is nothing I can find wrong with what I've done  open to being proven wrong if it means I get this thing working.
My TL072 voltages are all fine. Even tried swapping them around (IC1/2) and then replacing them but nuffin.

[aion]

Are the backs of the pots insulated? I can't tell from the pics but that could cause some issues. Otherwise everything looks great visually.

Next thing would be to check the voltages. Here's a set of known-working voltages (based on a a 9.00V supply, so yours could be +/- 0.6v and still be fine)

IC1 - TL072
1 = 4.49
2 = 4.49
3 = 3.54 stable, 3.95 initial (cap charge bleeding down through the meter)
4 = 0.00
5 = 4.49
6 = 4.49
7 = 4.49
8 = 9.00

IC2 - TL072
1 = 4.55
2 = 4.49
3 = 4.49
4 = -8.59
5 = 4.49
6 = 4.49
7 = 4.44
8 = 16.23

IC3 - TC1044SCPA
1 = 9.00
2 = 4.59
3 = 0.00
4 = -4.22
5 = -8.59
6 = 4.09
7 = 5.59
8 = 9.00

[Simmul8]

Thanks Kevin. Just redone and recorded my voltages.
Battery 9.14v

IC1 Tl072cp
1 4.32
2 4.53
3 3.46
4 -0.0
5 4.51
6 4.52
7 4.63
8 9.02

IC2 TL072cp
1 4.54
2 4.51
3 4.51
4 -8.62
5 4.50
6 4.51
7 4.49
8 16.19

IC3 TC1044SCPA
1 8.99
2 4.64
3 0
4 -4.18
5 -8.60
6 4.18
7 5.70
8 8.99

And yes my pots are insulated. Did a visual and multimeter check for continuity

[Simmul8]

I have recorded a video explaining what's happening so it's a bit easier to understand. http://youtu.be/RGiLp-LV6g4
This was recorded after all of the above troubleshooting.
The output jack is hard wired to ground as it it out of the metal enclosure.
Excuse the bad playing, quiet voice, and weird New Zealand accent.
Hope you guys can help

[Frank_NH]

Hmmm.  Could you check the voltages at each pin (the 6 legs) of your gain pot with your DMM and post them? Thanks.

[Simmul8]

each leg of the dual gang pot reads 4.42v and doesn't change at all when the pot is turned.

[Frank_NH]

I'd suspect a bad gain pot - especially since it hummed when you touched it in the video.  Check the resistance between lugs 1 and 3  and 4 and 6.  Note also that lugs 2 and 6 should be at the bias voltage (4.5V), and there ought to be different voltages on the other pins depending on the wiper position.  Good luck - I think you'll find the problem.

[jez79]

Not sure if this will help, but here's a guts shot of the Refractor I just finished minutes ago. Works like a charm. Cheers.

http://www.talkbass.com/media/refractor-guts.6335/

[Simmul8]

Thanks Frank, Have already removed the pot and measured the resistance and it all checks out fine.

[aion]

In this case, based on that video, there is definitely something amiss in the drive section. The voltages look fine so the next thing I would do is go back and reheat all of the solder joints surrounding the gain section - if you're looking at the schematic, you can skip anything to the right of the R16/C12 junction, but do everything from the start of the circuit up to that point.

I had this happen with the OD-820 (a somewhat similar circuit) - everything looked good visually, I had built dozens of pedals and knew what I was doing, etc. but in exasperation I just went through and reflowed all of the joints and magically it started working without issue. Never did figure out what the problem was exactly, but sometimes those weird random issues can only be fixed by weird random actions

[Frank_NH]

Thanks Frank, Have already removed the pot and measured the resistance and it all checks out fine.

Here's what I'd do at this point.

* First, check all the resistors in the gain stage.  They seem fine to me but you never know.  Look for a solder bridge - something must be affecting the op amp feedback loop such that the gain never goes above one.
* Don't solder the dual pot back in.  Instead, solder 6 wires and attach two 100K single pots with the wires in proper order for each.  See if you can get gain from the op amp.
* Check continuity between adjacent components with your DMM.  If there is a micro break in the PCB, you should be able to find it eventually.

I know these problems can be annoying, but you'll eventually find it! 

Speaking of the OD-820, built the Aion Nimbus overdrive and thought it sounded kind of blah compared to the Refractor, Stratus and other things I had built.  Not very gainy.  So I set it aside.  A few nights ago I decided to look at it again - and discovered that I had put the clipping diodes in wrong!  I fixed it  and it now sounds 100% better.   

[Simmul8]

but sometimes those weird random issues can only be fixed by weird random actions

A very philosophical approach to troubleshooting Kevin I'll give everything a try including what Frank said and will let you know how it goes.

[Simmul8]

http://m.imgur.com/gallery/iOn72OF
As shown in the photo, I've wired off board all the pots to completely eliminate the chance of shorting on the rear. I've also replaced the original dual gang pot with two 100kB single gang pots and then tried a second dual gang 100kb pot I had. With the pots no longer mounted I touched up all the solder joints for a third time. Then I went through the gain section and replaced 4 of the original capacitors for new  ones of equal value.
Wired it all up. Plugged it in.
Same problem. 

[Frank_NH]

Try rigging up two separate pots 250K pots instead of the dual.  It could be your dual pot is bad...