Hello, I'm new to electronics and eevblog forum (although I already watched a lot of Dave's video

). I am trying to figure out how the astable circuit works. I created a circuit in TINA v11 and simulate it using Transient Analysis but the result has problem.
When I set the end time to 2s, the result looks somewhat OK. VF1 and VF2 will oscillate. But when I set the end time to larger value like 10s, both VF1 and VF2 always at same level. Circuit and simulation results attached.
Is the problem of my circuit? Or I need to adjust some TINA parameters to make it right?
Sorry in advance if the post should not be here or anything inappropriate.
