Madbean Moodring Woes

[cnspedalbuilder]

Hello, I built a Madbean Moodring circuit and can't get any sound out in my tests.
-Haven't boxed it yet.
-Schematic and ideal voltages at http://www.madbeanpedals.com/projects/_folders/Delay/pdf/Moodring2017.pdf
-There may be a transistor issue, but I doubt that's the entire problem. I put a socket for Q1. I bought an SMD J201 and adapter from Smallbear and that didnt work. Also tried out an MPF102, and that didn't work. I've tried to be careful about pinouts but admit I'm not 100% sure.
-Because it is not boxed yet, I did tentative solder jobs on the pots, but all should work.
-I did not install dry kill switch yet. But when I short the pads, I get only dry sound and nothing else. Open it's just nothing. I think this means that the dry signal path is ok andreverb path is messed up.

Here are voltages, and as you can see they are pretty weird:
IC1: (TL072)
4.14
4.14
3.8
0
4.1
4.1
4.1
8.2

IC2: (Brick)
5
.8mV
--ignore
.8mV
.8mV
.8mV

IC3: PT2399
4.2
2.46
.87 mV
.75 mV
4.2
2.46
3.96
5
4
.7
.7
.52
4
1.82
.56

IC4:
3.8
3.8
3.48
.8mV
3.4
3.8
3.8
7.5

Q1:
.6 mV
.6 mV
0mV

Any advice on where to start? Thanks and happy thanksgiving!

[patrick398]

Not familiar circuit but you should have VC on Q1 drain. How are you listing you pins?

D
S
G?

[samhay]

I'm a little confused as to why you have different voltages on pin 8 of each TL072, but nothing is glaring other than Q1, which won't have any affect on dry signal.

I would suggest you put together an audio probe and trace the signal from the input.

[patrick398]

Pins 9 through 16 on the 2399 should sit at half regulator voltage, 2.5ivsh. They're all over the place on yours. Pin 8 is somehow at 5v? even though you're regulator is only supplying 4.2v at pin 1.
I'd still start with getting juice to Q1 though.

And +1 on the audio probe!

[cnspedalbuilder]

Sorry yes I listed as DSG. Could the Q1 voltages have something to do with the transistor itself or would they be the same regardless?

I will double check all my voltage readings to make sure that I didn't mess up some of my transcriptions.

And yes, I was hoping there was an obvious mistake, but ugh, I'll try the audio probe.

[patrick398]

Some pics of both side of your board might help spot something obvious

[cnspedalbuilder]

[cnspedalbuilder]

Sorry its not ansel adams or anything. Couldn't quite getlighting and focus right. Obviously I'm in a technical slump lately!

[cnspedalbuilder]

[Slowpoke101]

You have the 2399 delay chip installed backwards.

[patrick398]

Good spot. On the pt2399 the 'top' is indicated by the half circle indent not the full circle at the other end. Half circle should be facing into the board not out of it.

What are the voltage readings on that transistor socket with nothing inserted?

[cnspedalbuilder]

It's a thanksgiving miracle! I can't believe I didn't catch that. Thank you!!! So, good news is it sounds like reverb when the MPF102 is not in there. With the MPF102, I get howling feedback. So something is off there. But we are close!

I will inspect, but in meantime:

[cnspedalbuilder]

So it looks like there is a mismatch between the SMD adapter pinouts for the J201 and the order of pads on the PCB. But I tested it by popping the J201+adapter in a breadboard and jumpers to the corresponding points in the transistor socket. The reverb circuit definitely works (good) but I don't think it sounds much different than if I did not have it in there at all. Here are the voltages:

Gate: .4 mV
Drain: 7.46 V
Source: 350 mV

test rig Battery voltage=8.01

Should I be satisfied and box it? It seems weird that the reverb apparently works w/o the transistor at all, so I am not 100% sure that it is working properly now with the j201. (As an aside, my tester did not recognize the smd JFET, though I take that with a big grain of salt.)

[Slowpoke101]

If you are satisfied that everything is working then box away. The FET is part of the circuit that applies a small amount of delayed audio back to the start of the delay circuits themselves. This increases the reverb duration depending upon the setting of the dwell control. If the duration changes with adjustment of the dwell pot then all is good. If it doesn't change then you have to check more components (including the FET).
The circuit will work without the FET but reverb duration cannot be adjusted without it.

[cnspedalbuilder]

Thank you so much for your advice! The SMD j201 looks like it works! I had to rig wires to go from the adapter PCB to the transistor sockets but I think that worked out fine.