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.
"

 

[MBFX]

Trimpot shouldn't matter. This is from another thread on the subject, though, courtesy of @mkstewartesq :

Which JFETs are you using - 2N5952 or 2N5457s? Both will work but I believe the pinouts are opposite.

OK, probably two stupid questions but, just to be safe:

1. Did you move very slowly through the trim pot sweep? The area in which there is phasing is actually a very tiny amount of the sweep. You get no phasing, then in a very tiny area, phasing, then no phasing again. The 200 K pot should be fine(in fact, I believe that’s what I and others used as well.)

 

[squirrelboy]

Thank you for the reply!

I am using 4x 2N5952.

I have gone very very slowly through the trimpot. It is a 1 turn trimpot with about 180 degrees of available turn. So, even the tiniest amount of turn is probably having a huge difference. Would it potentially be worth it to find a trimpot that has a lot more turns so I can be even finer with my adjustment?

 

[jimilee]

When you say you got them online, from where and was it a reputable place? Also, when you turn the trim part manually back and forth quicker, can you hear the phase happen.

 

[VanWhy]

Coming from someone who just experienced a similar issue, the trimpot didn't make a ton of difference. I have a 200K in mine and when you hit that sweet spot, you know it. The window is small but big enough that its hard to miss if you are going slow.

The only thing that I found fixed was replacing the transistors. I had a nice matched set from Lectrix FX that did the same thing. Only when I replaced them it started to phase.

 

[squirrelboy]

When you say you got them online, from where and was it a reputable place? Also, when you turn the trim part manually back and forth quicker, can you hear the phase happen.

I got them from Pedal Parts and Kits online. It seemed reputable but Idk.

Yes, when I turn the pot back and forth quickly I can hear it phase.

 

[jimilee]

I got them from Pedal Parts and Kits online. It seemed reputable but Idk.

Yes, when I turn the pot back and forth quickly I can hear it phase.

That’s a good sign. Try turning the trim pot even slower, like insanely slow. If that doesn’t work, you may have to replace the trimmer.

 

[mkstewartesq]

Try turning the trim pot even slower, like insanely slow.

This ^^^.

My advice is to try turning the pot while you count to 1 million. If you hit 1 million before you have turned the pot the full rotation, you have turned it too fast and must start over.

Mike

 

[MBFX]

I do like multiturn trimpots. Much easier to dial stuff in.

Have you tried removing and reseating your ICs? You might even try sanding the legs a little.

 

[music6000]

A 3362 300 degree trimpot is way better than 180 degree.
Im curious about the resistors in series being the correct values also???

 

[jimilee]

I’m curious, what are the voltages on your fets?

 

[squirrelboy]

I’m curious, what are the voltages on your fets?

With where I have the pot set now, the voltages are as follows:

Drain: 4.2
Source: 4.2
Gate: fluctuates between 2.13 and 2.17

 

[squirrelboy]

A 3362 300 degree trimpot is way better than 180 degree.
Im curious about the resistors in series being the correct values also???

I didn’t have 24k resistors so I soldered a 22k and 2k resistor together for those. I also didn’t have a 3.9m resistor so I soldered together two 2M resistors to equal 4M (my thought is that this is close enough?).

 

[squirrelboy]

The latest thing I did was replace my 200k trimpot with a regular B250k pot. Now, something very strange is happening. When I hold the 250k pot in my hand, the slightest movement of my hand makes the pedal phase a bit. I’m not even turning the knob. I realize this sounds crazy.

 

[chris.knudson]

It's impossible to tell without seeing the other side of the board, but you might want to check for cold solder joints on your ICs. Pins 2 and 4 on all three of your ICs don't have a good solder flow through the hole like the rest of the pins do. I always like to see a little solder peeking through to the top side of the board.

 

[chris.knudson]

Oh, and by the way, thanks for this post. I have an XC Phase on my bench right now, and I compared yours to mine to see if I could spot anything that looked off. and I noticed that I had a TL072 where the TL022 is supposed to go. Fortunately I have them socketed, so it was an easy fix to swap them out.

 

[jimilee]

The latest thing I did was replace my 200k trimpot with a regular B250k pot. Now, something very strange is happening. When I hold the 250k pot in my hand, the slightest movement of my hand makes the pedal phase a bit. I’m not even turning the knob. I realize this sounds crazy.

Don’t worry about the resistors, or the trim pot. You should probably put the trim pot back. That fact that your readings are fluctuating means your LFO is working.

No need to randomly remove and replace things. You run the chance of doing more harm than good. You’re going to want to go through and reheat all your solder joints to ensure there are no cold joints. Don’t worry about if the look like they need it or not. Hang with us, you’ll get there.

 

[chris.knudson]

The latest thing I did was replace my 200k trimpot with a regular B250k pot. Now, something very strange is happening. When I hold the 250k pot in my hand, the slightest movement of my hand makes the pedal phase a bit. I’m not even turning the knob. I realize this sounds crazy.

Holding the pot in your hand (depending on how you're holding it) can change its resistance due to the resistance of your skin.

 

[squirrelboy]

Don’t worry about the resistors, or the trim pot. You should probably put the trim pot back. That fact that your readings are fluctuating means your LFO is working.

No need to randomly remove and replace things. You run the chance of doing more harm than good. You’re going to want to go through and reheat all your solder joints to ensure there are no cold joints. Don’t worry about if the look like they need it or not. Hang with us, you’ll get there.

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.

 

[Giorfida]

That’s a good sign. Try turning the trim pot even slower, like insanely slow. If that doesn’t work, you may have to replace the trimmer.

I just picked up a 15 turn 250k trimmer I’m going to try to fit in mine. Mine sweeps but I think I can get more. And with the sensitivity, if hate for a John Bonham wannabe making it vibrate out