Duo Phase LFO B Constant LED

[chongmagic]

I am putting together my second Duo Phase, first one worked great, sold it and wanted another.

LFO A works fine and if I toggle to sweep switch both will work fine. I did sub the B25Ks for A25Ks, but I doubt that is the issue. Looking at the schematic it might be one of my TL072s is bad. I did replace the 4401 transistor just out of curiosity and it still stays constant with the LED if I toggle the sweep switch, the sync switch seems to just make the LED brighter on side B.

I am still not the greatest with reading schematics, but it looks like if one of the TL072s is bad it would be, IC6B or IC5B.

 

[chongmagic]

Yeah I know and this is the place where the copper was showing a slight trace before I populated the board. I didn't think much of it at the time, but it could be the cause.

 

[chongmagic]

New video by Jonathan Freeman (Chongmagic)

photos.app.goo.gl

 

[Chuck D. Bones]

The sound in the video is coming from where? The ch A output or the probe? Are the two channels separate or wired in series?

 

[chongmagic]

The sound is coming from a Boss looper that I have connected into the audio probe. The other end is a Boss Katana battery powered amp. Two channels are set that they can each be independently connected. Like the four plug wiring diagram in the build docs.

 

[Chuck D. Bones]

So you're using the probe to inject sound from the looper and listening to the output of the Duo-Phase with the Katana?

 

[chongmagic]

Correct

Substituting the looper for a guitar basically

 

[Chuck D. Bones]

I'm used to the idea of connecting the probe to an amp and using it to listen to points in the circuit. What you're doing is perfectly valid, as long as you inject into parts of the circuit that are relatively high impedance.
What happens if you connect the looper to the Duo-Phase input with a regular 1/4" cable? Does it work then?

 

[chongmagic]

It only works on the B signal path, no output passes through A.

 

[Chuck D. Bones]

In the video it looks like you installed a 3.9K for both R1A & R2A.

 

[Chuck D. Bones]

If that's not it, then check the wiring of the channel A input connector. With the stomp switch in the Engaged position, you should have continuity from the input connector to the left side (viewed from the top) of C1A and 3.9K from the right side of C1A to IC1A-5.

 

[chongmagic]

I will double check those and check continuity. I may take a break from this one for a day then come back.

 

[Chuck D. Bones]

I'm going out of town for a few days. I won't be checking in here much during that time.

 

[chongmagic]

The resistor values are correct and I am getting continuity from C1A to input. Will check the resistance to IC5a pin 5.