U13.2: use a multimeter make sure pins 6 and 7 have no resistance between them on U13 TL074.
U13.3: use a multimeter make sure pins 8 and 9 have no resistance between them on U13 TL074.
Note: I am making some assumptions about which of the op-amps in the TL074 are “B” and “C” - without reverse engineering the PCB layout I can’t be absolutely sure that U13.2 = pins 5,6,7 and U13.3 = pins 8,9,10. @creatorlars?
Your problem could be caused by a faulty trimpot R3, yes. With a multimeter set to measure resistance and the module completely disconnected from power (very important!) measure the resistance between the wiper (middle pin) and each of the outer legs, as you adjust the trimpot. If adjusting it doesn’t change the resistance your meter reads then it might be faulty. Note that the resistance between the two outer legs (excluding the wiper) will always be the same (approx. 10K) and doesn’t change as you adjust the trimpot, though.
The other thing you could do (which I think I implied but didn’t explain fully) is to check each connected ‘net’ - for example, the output of U13.2 should be connected to one of R3’s outer legs, and so on. There are a lot of connections you can check like this, with a multimeter. If there are two pins that should be connected (0 ohms resistance) but they aren’t then either there’s a bad solder point somewhere, or a broken track (less likely).
Once you’ve tried replacing components and checking all the connections, really the next stage in debugging will need a scope…
Thanks again.
Ok, I checked resistance on 13.2 and 13.3 and got 0, so those appear to be functioning correctly. I checked the trim pot and it appears to be functioning normally as well. My plan now is to check every resistor and every connection on that part of the circuit.
One thing I noticed is that voltage on the vertical output jacks, all three is very high compared to the out put of the horizontal jacks. Not above +5 or anything. Is that because the vertical levels require a higher voltage or is that an indicator of my issue?
I think I may have stumbled across the culprit. I was checking my resistor value around the board and I am finding several of my 10k resistors are reading 6.8k-7.6k on my multimeter. The ones at R28, R29, and R22. I’ll replace those and see what happens.
Are you checking the resistance while they’re in the circuit? You’d likely be reading incorrect values if they’re still on the PCB since they’re interacting with other components.
Damn. Got excited there for a second.
Sometimes it can take a lot of work to get these things going 
Sorry you’re having difficulties… we’ve all been where you are! If you have the finances, it might be worth considering building a second ramps module. Your soldering skills will get better with each module you make up and it’ll be a completely independent set of components so a second chance to see how it goes.
Other than that, I think you need to obtain a scope now. You’ll get a lot of use out of it when building other modules so it’s worthwhile. Even a $50 cheapo second-hand low bandwidth (e.g. 10MHz) analog one would be enough for the debugging you need to do now.
I would second this approach if your situation allows it. I’ve had non-working builds that were a snap to fix once I had built up a second one to compare it with, especially with an oscilloscope. Going part by part and comparing signals between both modules will invariably show you where something went wrong. You could probably sell the spare Ramps once you fix your first one, as well.
Keep at it and hope you figure it out!
Thanks, that is probably what I will do. I built 8 of these guys and this is the first one where I couldn’t figure out where it went wrong. I did screw up on building the VCO and ordered a new one, and it is always easier the second time around. Which is where I am probably going with this one. I did order a cheap oscilloscope, since that is clearly something I need.