SOLVED XC Phase not phasing

[squirrelboy]

Hi Everyone,

I have looked through the previous posts about this issue and I don't think my issue has been resolved. I am using 4 matched 2N5952s that I ordered online. I am using a 200k trimpot instead of the 250k that the documentation calls for. I am using 2 TL072s and 1 TL022.

The pedal is turning on and sound is getting through. When I slowly turn the trimpot, I can kinda manually make the pedal phase, but it doesn't do it on its own. As in, I can hear a bit of the sweep of the phase, but only when I turn the trimpot around the "sweet spot."

As you can tell from the picture below, I had to wire some resistors in series to get the correct values. I also had to do some weird wiring to use the 3PDT breakout board that I have. The LED works fine.
"

 

[chris.knudson]

I originally installed a TL072 before realizing it should be a TL022

I did the same thing...until I saw this thread, so thank you for that!

 

[music6000]

Ok I just reflowed the joints on the ICs. Here are a couple of pics of the back of the board. The roughest area is where the TL022 is seated. I originally installed a TL072 before realizing it should be a TL022. It looks rough, but I confirmed that each pin has continuity with the component to which it is traced.

Still having the same problem. I can make it phase manually, but not on its own.

As you had to remove the TL072 & replace it with the TL022, with Power unplugged, Test for Continuity on matching colours:

 

[squirrelboy]

As you had to remove the TL072 & replace it with the TL022, with Power unplugged, Test for Continuity on matching colours:

View attachment 62810

I just checked all of these points and there is continuity between all of them except for IC3.1 to the adjacent lead of R10. However, there IS continuity between IC3.1 and the OTHER lead of R10.

 

[chris.knudson]

I just checked all of these points and there is continuity between all of them except for IC3.1 to the adjacent lead of R10. However, there IS continuity between IC3.1 and the OTHER lead of R10.

That is correct. Pin 1 on the TL022 connects to Pin 3 of the Stages switch and the far side of R10 (i.e. not the pin next to the IC).

 

[chris.knudson]

Just out of curiosity, have you tried tweaking the trim pot with the stages switch in the other position and likewise with the Block|Script switch? Throwing those switches routes the signal through different parts of the circuit, and understanding what (if any effect) that has could help narrow the problem?

There doesn't appear to be anything physically wrong with your circuit. I am curious about the two big electrolytic caps - I can't read the values and I can't tell if they're touching the leg of either of your switches. I used tantalums in my build.

 

[squirrelboy]

Just out of curiosity, have you tried tweaking the trim pot with the stages switch in the other position and likewise with the Block|Script switch? Throwing those switches routes the signal through different parts of the circuit, and understanding what (if any effect) that has could help narrow the problem?

There doesn't appear to be anything physically wrong with your circuit. I am curious about the two big electrolytic caps - I can't read the values and I can't tell if they're touching the leg of either of your switches. I used tantalums in my build.

Those are both big 15uf electrolytics. I think what I’m going to do at this point is order another PCB and some tantalum 15 uF caps and give it another go!

 

[music6000]

Chris is correct, this is the old mask & has changed on your version.

 

[chris.knudson]

Those are both big 15uf electrolytics. I think what I’m going to do at this point is order another PCB and some tantalum 15 uF caps and give it another go!

Don't give up -- I think were close to solving this.

 

[music6000]

My concern here is the tl072 opamps could be be bogus, it has happened to other Members here???
It has the texas instruments logo but they do not have the indent at the top.
Texas Instruments have the dot at pin 1.
It is the norm to put sockets in these positions to be able to change out opamps & not damage them soldering directly to the PCB

 

[chris.knudson]

Don't give up -- I think were close to solving this.

The electrolytic caps should be fine so long as they aren't touching the legs of the switches.

This phasing issue seems to be a common problem based on the threads I've been reading, and there seems to be some issues with the different stages. Some people report that that they can get the block to work and not the script. I'm just curious to see if we can narrow the problem down to one specific part of the circuit. In my mind, it has to be one of a few things...

1 one of the ICs is bad (always a possibility -- and a good argument for socketing your ICs)
2 one of the FETs is bad - your source seems reliable, and in order to match them, they had to test them
3 The transistor is bad
4 you're not getting the right resistance on the trim pot

Since you tried a 250K pot, let's just assume that isn't the problem.

I really want to get this pedal working for you. I have one on my bench that isn't finished, and I'm hoping to learn as much as I can so I can have a successful build too.

 

[chris.knudson]

My concern here is the tl072 opamps could be be bogus, it has happened to other Members here???
It has the texas instruments logo but they do not have the indent at the top.
Texas Instruments have the dot at pin 1.
It is the norm to put sockets in these positions to be able to change out opamps & not damage them soldering directly to the PCB

I've found that the TI logo means nothing -- the counterfeiters have found a way to copy that too. I buy my ICs in batches of 10, and I source them from different suppliers -- when one doesn't work, I swap it out with another. The only issues I have ever had with a build so far (knock on wood) have been with bad IC chips.

 

[music6000]

The electrolytic caps should be fine so long as they aren't touching the legs of the switches.

This phasing issue seems to be a common problem based on the threads I've been reading, and there seems to be some issues with the different stages. Some people report that that they can get the block to work and not the script. I'm just curious to see if we can narrow the problem down to one specific part of the circuit. In my mind, it has to be one of a few things...

1 one of the ICs is bad (always a possibility -- and a good argument for socketing your ICs)
2 one of the FETs is bad - your source seems reliable, and in order to match them, they had to test them
3 The transistor is bad
4 you're not getting the right resistance on the trim pot

Since you tried a 250K pot, let's just assume that isn't the problem.

I really want to get this pedal working for you. I have one on my bench that isn't finished, and I'm hoping to learn as much as I can so I can have a successful build too.

I always blow these up to a bigger size!
it appears that the lower tl072 is a different brand to the one above it, I have my suspicions!!!

 

[chris.knudson]

I always blow these up to a bigger size!
it appears that the lower tl072 is a different brand to the one above it, I have my suspicions!!!

It's possible that could be the problem -- we just need to figure out what part of the circuit is causing the problem. Desoldering and replacing an IC isn't fun, but it's not impossible either.

 

[music6000]

I have just made it easier if a problem arises
This would work if room is not an issue:

Build A Pot Removal Tool

I found a piece of 1'' x 1/4 Copper Flat bar in my shed, Clamped it facing up in the Vice & attacked it with a 5'' Cut Off Disc in my grinder, Got the shape real close & lopped it off. Got a pair of Plies (Highly Recommended) & put it in the Vice & put a 60 degree chamfer across the Flat to form...

forum.pedalpcb.com

 

[chris.knudson]

I have just made it easier if a problem arises
This would work if room is not an issue:

Build A Pot Removal Tool

I found a piece of 1'' x 1/4 Copper Flat bar in my shed, Clamped it facing up in the Vice & attacked it with a 5'' Cut Off Disc in my grinder, Got the shape real close & lopped it off. Got a pair of Plies (Highly Recommended) & put it in the Vice & put a 60 degree chamfer across the Flat to form...

forum.pedalpcb.com

While that is cool. I have tricks up my sleeve to remove and replace an IC that may not be pretty, but they don't cost a dime, and everybody has them on their bench already.

 

[chris.knudson]

I have just made it easier if a problem arises
This would work if room is not an issue:

Build A Pot Removal Tool

I found a piece of 1'' x 1/4 Copper Flat bar in my shed, Clamped it facing up in the Vice & attacked it with a 5'' Cut Off Disc in my grinder, Got the shape real close & lopped it off. Got a pair of Plies (Highly Recommended) & put it in the Vice & put a 60 degree chamfer across the Flat to form...

forum.pedalpcb.com

BTW, I want one of these...

 

[music6000]

BTW, I want one of these...

I knocked it out and had it working in about 40 minutes including the 10 minute warm up!

 

[chris.knudson]

I knocked it out and had it working in about 40 minutes including the 10 minute warm up!

View attachment 62853

I'm not anywhere near as handy as you are.

 

[squirrelboy]

This is the only time I have ever not used sockets. I ran out of sockets and didn’t want to wait for new ones to arrive. Lesson learned!

I definitely bought some of the TL072s that I have from Amazon. I pretty much expect them to be bogus but they’ve worked in other builds.

Ok, when I get home from work tomorrow I am going to desolder at least the TL072s and put sockets in there and then try some different TL072s.

Thanks so much to everyone for the help!

 

[chris.knudson]

This is the only time I have ever not used sockets. I ran out of sockets and didn’t want to wait for new ones to arrive. Lesson learned!

I definitely bought some of the TL072s that I have from Amazon. I pretty much expect them to be bogus but they’ve worked in other builds.

Ok, when I get home from work tomorrow I am going to desolder at least the TL072s and put sockets in there and then try some different TL072s.

Thanks so much to everyone for the help!

Nothing wrong with buying ICs from Amazon -- I do it all the time (as a Prime member, you can't beat the free shipping). You just have to expect that a certain percentage of what you buy is going to end up being garbage.