U-Boat (ValveWizard sub-octave) help

[nspacestd]

Hi all! I'm new to the forum, so please excuse me if I've posted in the wrong section.

Anyway, I've just finished building this stompbox http://www.valvewizard.co.uk/uboat.pdf (U-Boat sub octave, by the Valve Wizard), and I can't get it to work properly.
The only modification I've done is that I'm running the circuit off a 9V battery rather than a wall wart. The parts are exactly those specified in the BOM, I've omitted R19 as specified.

The problem is that with the effect active and mix control all the way CCW or with the effect bypassed, I can only hear a very faint sound (if I plug the guitar into the effect and the effect into my amp I only get a low volume clean sound with the amplifier gain set pretty high, while if I plug my guitar straight into the amp with the same settings I get a heavily overdriven sound). With the effect active and mix controll all the way CW (100% effected signal), I only get a short, very low volume buzz when I play a note. There is also quite some background hum, but I guess this is because the circuit is not into a metal enclosure yet.

Here are some voltage readings (all measurements are in volts and taken with effect bypassed and input shorted to ground):
Battery not connected to anything: 8.95
Circuit board end of red battery lead: 8.87
Circuit board end of black battery lead: 0.00

U1: p1: 4.44
p2: 4.44
p3: 1.79
p4: 0.00
p5: 4.16
p6: 4.44
p7: 4.45
p8: 8.86

U2: p1: 4.43
p2: 4.43
p3: 4.43
p4: 0.00
p5: 4.41
p6: 4.43
p7: 4.43
p8: 8.85

U3: p1: 4.41
p2: 4.43
p3: 4.41
p4: 0.00
p5: 4.41
p6: 4.41
p7: 4.26
p8: 8.84

U4: p1: 8.22
p2: 4.41
p3: 4.07
p4: 0.00
p5: 4.37
p6: 4.39
p7: 0.16
p8: 8.82

U5: p1: 0.00
p2: 8.82
p3: 0.00
p4: 8.13
p5: 0.00
p6: 0.16
p7: 0.00
p8: 0.00
p9: 8.81
p10: 0.00
p11: 0.00
p12: 8.81
p13: 0.07
p14: 8.81

Q1: D: 2.42
S: 4.37
G: 0.00

Q2: D: 4.37
S: 4.37
G: 4.33

D1: A: 0.00
K: 0.00

D2: A: 0.00
K: 8.80

D3: A: 4.02
K: 4.30

D4: A: 4.30
K: 4.39

D5: A: 4.37
K: 4.35

D6: A: 4.35
K: 4.37

D7: A: 4.38
K: 4.04

D8: A: 4.04
K: 4.38

D12: A: 0.64
K: 0.07

D13 (LED) A: 0.00
K: 0.00

I have already spotted a weird voltage at U1: isn't the first half (pins 1,2,3) supposed to be outputting the same voltage that appears at the input? If so, then why do I have two different voltages at input and at output? I've tried measuring the voltage at pin 3 even with no opamp in the socket, but it stays the same. The 4.5V supply seems to be fine though. I've tried swapping R3 with a 1M 1W resistor I had at hand, but there was no difference.

Any help is greatly appreciated!

[PRR]

> p3: 1.79

Lift one end of C1. Does voltage change?

Change R3 to 100K or 10K. Does voltage change?

If it is solidly 1.7_ Volts, it smells like it is shorted to an LED, but I don't see how that could happen.

[nspacestd]

With one end of C1 lifted the voltage stays the same, but when changing R3 to 100k (C1 still disconnected) the voltage at pin 3 of U1 becomes about 3 volts, and with no opamp in the socket it goes at 3.5. So it seems there is some current flowing through R3. I had already redone all the solder joints around U1 twice before posting here, so I think they are not the problem

[PRR]

Replace U1.

[merlinb]

I have already spotted a weird voltage at U1: isn't the first half (pins 1,2,3) supposed to be outputting the same voltage that appears at the input?

That's normal. Pin 3 is a high impedance node, so your multimeter drags the voltage down and gives a false reading.

Let's be systematic and try to get the dry signal to work correctly before anything else.

Remove all chis except U1 and U2, and report back what happens in both active and bypass modes. What JFET are you using for Q1, and is it wired correctly? Is D1 the right way round? Does the LED switch on and off the way you expect?

[nspacestd]

Hi, guys. Thanks for your help, much appreciated. Excuse me for the late reply, but I wasn't at home last week and didn't have the circuit at hand.

I've tried each of the 3 TL072s in the U1 position, but nothing changes. Then I followed PRR's suggestion and swapped R3 with a 100k (brown - black - yellow), and now the dry signal seems to work fine (the wet signal is still very low in volume, and the trimmer is maxed). However when changing R3 I lifted one of the solder pads, and looking at the PCB with a lens I noticed several imperfections in the traces, so I plan to restart from scratch and etch a new board.