Aion refractor issue

[jdix123@gmail.com]

Hi all. Building this project as pcb only (I supplied components).

Buffered bypass signal ok (I jumped the  place on the PCB, did not install a switch). There is signal when the pedal is engaged but there is dramatic volume loss. I can hear the volume knob affecting the volume level, and can hear that the gain affects the volume as well but no grit is introduced. I can't tell if the treble pot does anything when I sweep it.

Both Op amp chips are TL072, charge pump is a 7660S.

IC1:
4.75
4.75
3.4 (reducing)
0
5.54
4.73
6.6
7.73

IC2:
6.29
5.76
4.64
6.39 (this should be ground, no?)
4.64
6.25
6.29
6.9 (this should be like 16 or something)

IC3:
7.71
7.71
0
7.1
6.31
7.71
7.19
7.71

I tried to audio probe it, and it seems to be behaving as it should at IC1:1-5. I do not hear signal clipping at the diodes (I socketed D1&2 and have tried multiple diodes in that spot so I know it isn't just a bad one or two).

Nothing gets hot, and I haven't released any mystical blue smoke. Project isn't boxed yet so I know I'm not grounding out on the case. I'm stumped.

[duck_arse]

welcome to the forum. please be so kind as to include, or link to, the circuit diagram or at the very least the build docs, for the exact version of the circuit, whatever it may be, you are building. people loose interest if they have to go looking and guessing.

and then, please, post photos of what you have built. then, we might get somewhere.

[idy]

IC 3 is the charge pump. It is not pumping.You should be seeing negative voltage on pin 5.
Yes, Both opamps need low voltage on pin 4 and high on pin 8.
IC 1 gets 0 and +9. IC 2 gets almost around -9 and +18.

Are you using battery or power supply? What does it read out of circuit? (power supplies often read high when unloaded, don't worry too much yet.)

[jdix123@gmail.com]

Thanks for the responses.

This is the build documentation (PCB only).

Voltage readings are similar whether using a battery or a power supply.

Here are some pics.

[antonis]

Here are some pics.

Many prospective shorts...

[ElectricDruid]

Many prospective shorts...

+1 agree. The soldering is lumpy. Probably you need a bit more heat so it flows more easily. Hold the iron on the joint for just a second longer.

Check first around that IC3 charge pump to see if you can find any problems, since until that's working and you've got the voltages you expect from the power supply, you can't test the rest of it.

[jdix123@gmail.com]

I'll see about reflowing - in the pics, a lot of flux/rosin is reflecting like solder - it's not actually as bad as it looks. I'd love to clean it up but I'm not sure how - wick doesn't seem to do it.

[jdix123@gmail.com]

No luck with reflowing 

[ElectricDruid]

No luck with reflowing 

Shame! That would have been a nice easy fix.

Ok, so now get your multimeter and check for shorts around the charge pump IC. Most likely is something is connecting to something that it shouldn't be!

[jdix123@gmail.com]

No luck with reflowing 

Shame! That would have been a nice easy fix.

Ok, so now get your multimeter and check for shorts around the charge pump IC. Most likely is something is connecting to something that it shouldn't be!

I can't find anything. I've verified the circuit path around the charge pump is correct, but I can't find a short. I'm not even really sure how to go about it, other than just putting a lead on a point and randomly probing around.

[Slowpoke101]

At the moment I would suggest replacing IC3 with a new device, preferably from a different supplier. You may simply have been supplied a faulty IC. However before replacing IC3, remove IC1 and 2 then check if the voltages on IC3 have changed when you apply power. You don't need to do this, it's just for curiosity's sake.

One other thing: I couldn't really see from the photos but it looks as if the TONE control metal back cover may be able to touch the circuit board. If you haven't done so already, I suggest that you insulate the back of that control with a piece of card or thin sheet plastic. The last thing you want is a short circuit.

[jdix123@gmail.com]

I was leaning that way as well. I thought it unlikely that two separate chips where both bad in the same way, but I've been over and over and over the circuit. I'll order a new charge pump (like five of them) from a diff place and see if that changes anything.

[jdix123@gmail.com]

Unfortunately it is not the charge pump chip that is bad.

I still don't know why it isn't working here, but I built a Mu-Tron clone which has a charge pump in that circuit, so I pulled what I know is a working chip and plugged it in, but nothing. Similar readings on the multimeter.

[antonis]

I'd scrutinize charge pump's surrounding circuitry..

[ElectricDruid]

I'd scrutinize charge pump's surrounding circuitry..

It's a good idea. It'd be easy to put one of those diodes or caps in back-to-front and that could be enough to stop it working.
First check VA on pin 1. If you've got 9V there, check you've got 4.5V at VR. Those two voltages are independent of the charge pump, so they should be ok.
After that, you've got to check thhose 1N4001 diodes and the 10uF caps and see if you can't get those last two voltages up and running.

[jdix123@gmail.com]

Is C19 backwards on the schematic? I don't want to flip it blind but it looks wrong to me...

[Matthew Sanford]

It's good like that, ground is higher than -9 volts

[jdix123@gmail.com]

I can't find anything that isn't doing what it should (or I just don't know how to recognize it). I checked polarity of diodes and electrolytic caps. VA and VR seem correct, but I can't find where and why VA and VB are not.

I guess I can try pulling and replacing, one part at a time - I've never run into any issues like this before on any of my dozen or so builds, and it's got me 

[tootsMcgee]

For short finding it might be a good idea to try to clean up the board again. What solder are you using? That flux stuff is nasty especially if you use something "no-clean" but even "no-clean" falls to some isopropyl and a toothbrush.

Remove the ICs and test on a corner of the board to make sure it comes off. I usually apply the alcohol to the back of the board, wait a bit, scrub with the toothbrush in circles, then add more and alternate between scrubbing and then tilting the board and using the toothbrush to brush the alcohol off the edge of the board. You have to get rid of the flux once it is softened or else it hangs around and looks ugly. Lots of little scrub/rinse cycles and eventually it'll clear. You could also dab off the alcohol+flux mixture with a paper towel and then add more for the next scrub/rinse cycle.

Another thought: do you have those potentiometer dust covers available, or even some card stock or plastic sheet that you can slip between the PCB and the potentiometer? I'm wondering if the center pot is shorting something. When you test, is it in the enclosure or out?

I'm comparing components to my photos of my build but the colors are off on my camera and I no longer have the original pedal as it was a gift. I don't see anything obvious wrong but I'll keep looking.