Engineers Thumb Non-Madbean Help Please

[murdog47]

I built this Engineers Thumb and am not getting an output signal.  When tracing the signal it appears to end at the 3rd pin on both TL072's.  I tried different chips to rule out a bad chip and get the same results.
Voltages are as follows:

IC1: 1: 8.49 2: 8.49 3: 8.48 4: 8.87 5: 8.70 6: 8.50 7: 8.50 8: 9.37

IC2: 1: 8.19 2: 8.46 3: 8.48 4: 8.87 5: 8.47 6: 8.49 7: 8.15 8: 9.38

IC3: 1-8: 8.42,8.43,8.5,8.5,8.49,8.87,1.34,8.4
     9-16: 8.39,1.338,8.47,8.42,7.93,7.93,8.44,8.41

Q1: C:8.42 B:8.16 E:8.49

[midwayfair]

IC1: 1: 8.49 2: 8.49 3: 8.48 4: 8.87 5: 8.70 6: 8.50 7: 8.50 8: 9.37

IC2: 1: 8.19 2: 8.46 3: 8.48 4: 8.87 5: 8.47 6: 8.49 7: 8.15 8: 9.38

IC3: 1-8: 8.42,8.43,8.5,8.5,8.49,8.87,1.34,8.4
     9-16: 8.39,1.338,8.47,8.42,7.93,7.93,8.44,8.41

Q1: C:8.42 B:8.16 E:8.49

Most immediate issue: none of your ICs are grounded. (Pin 4 should be 0.) That's the first place to check ...  time to get out the multimeter. Somehow they're connected to the 9V instead of ground. if you didn't complete the cut under IC1, R13 will be passing the voltage on to your ground throughout the entire circuit. Kaboom!

[murdog47]

All of my cuts were good, found two of the jumpers that didn't get soldered.  Puling 0V at pin 4 on ic1 and 2 now. And a new set of problems....

Ratio Pot has to be set right around 12 o'clock or no signal
Threshold, Attack, and Release pots do nothing

Volume pot is working correctly

[midwayfair]

All of my cuts were good, found two of the jumpers that didn't get soldered.  Puling 0V at pin 4 on ic1 and 2 now. And a new set of problems....

Ratio Pot has to be set right around 12 o'clock or no signal
Threshold, Attack, and Release pots do nothing

Volume pot is working correctly

Theshold does nothing? Are you sure? Try setting it at max for now. It sets the Vb on IC1, I'm really not sure what running it too low does. If the threshold is too high, it would also make the attack and release sound like they aren't working, because you won't be getting any actual compression to change the characteristics of.

The ratio pot is a gain control of sorts, because it's only working when you turn up the gain (quite a bit), it sounds like you're getting gating somewhere in the feedback loop of IC1a. Again, new voltage readings on all pins might help. Are you getting 4.5v or thereabouts on any of your pins now that the chips are grounded? Is IC3 grounded now too? I know Harald verified his build, but IC3 pins 6--10 and 16 are grounded in the original schematic. Here I only see Pin6 being grounded.

[murdog47]

So here are my new voltages

IC1 1-4: 4.96, 4.68, 4.26, 00.1
     5-8: 4.45, 4.68, 4.68, 9.36

IC2 1-4: 4.68, 4.68, 4.26, 00.1
     5-8: 4.39, 4.67, 5.01, 9.36

Here's where it gets silly

IC3: 1-8:    1.102, no reading on 2, 4.66, 4.68, 4.64, 00.1, no reading on 7 and 8
       8-16:  No volatge readings on 8-16

[midwayfair]

So here are my new voltages

IC1 1-4: 4.96, 4.68, 4.26, 00.1
    5-8: 4.45, 4.68, 4.68, 9.36

IC2 1-4: 4.68, 4.68, 4.26, 00.1
    5-8: 4.39, 4.67, 5.01, 9.36

Here's where it gets silly

IC3: 1-8:    1.102, no reading on 2, 4.66, 4.68, 4.64, 00.1, no reading on 7 and 8
      8-16:  No volatge readings on 8-16

Pin 10 is the voltage supply to IC3, so if you've got no reading there, that's the first place I'd start. Sure enough, I don't see a solder blob on that part of your vero, though I think I see a little piece of jumper peeking out. Probably just a missed solder connection since the chip was in the way on top and it's hard to see that jumper.

If you still have problems after that point, it might help to find the other schematic, the one that shows all the connections on IC3. Sabro's layout is different from the etched verion (personally, I'd ground the Unused half of IC3 like in Merlin's etched version to help control noise even more), and the simplified schematic doesn't show some stuff that I think Merlin took as read. Here's my perf layout, it might be useful for some comparison since it's a little easier to see the connections than with vero.

https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20mini%20layouts/Nonmini%20builds/Engineer%27s%20Thumb.pdf

If your multimeter tells you everything connected as it should be, you might need to start a thread on DIYSB, or just post in Merlin's thread.

[murdog47]

Brilliant! Needed to solder the jumper in at IC3 pin 11! Working like a charm now! Funny how those little things sneak past and drive you crazy! Thanks for all of your help! 

[midwayfair]

Brilliant! Needed to solder the jumper in at IC3 pin 11! Working like a charm now! Funny how those little things sneak past and drive you crazy! Thanks for all of your help! 

Yay! It's one of my favorite pedals, so I'm glad to see other people picking it up.