I am to trying breadboard a square and triangle generator similar to this one.
While there were a couple of differences (such as a potentiometer) in my original schematic, this simplified one still simulates well. (Positioning of op-amps reversed.)
I've now built this circuit on a breadboard about 10 times. I've changed resistors and capacitor values, breadboard, jumpers, several TL072s & a TL074. I've checked there's 24V across the op-amp and that ground is in the centre.
At one point the circuit DID work as intended (a wonderful moment.) Unfortunately I'm unsure what circumstances changed (if any,) but it didn't last long. I was even able to change R10 and C1 to get the frequency down to 0.25 Hz which is about where I want it, but when I came back to it, no luck.
At the moment, I just get -10.7V (to ground) from the integrator and +11.3V from the square wave generator.
You might say there's just a bad connection somewhere but I've built this thing enough times to start doubting that. Is there anything that jumps out or might be less obvious? I noticed once when I switched power on, I got a split second triangle. Do I need to kick it into oscillation somehow?