LTSpice 555 Timer PWM LED Driver Output Not Switching at Threshold Voltage

I'm trying to design a PWM LED driver in LTSpice, but the 555 timer I'm using as the PWM doesn't seem to behaving as it should.

As far as I know, when the threshold pin reaches 2/3 of the supply voltage, the output should go low. However, that's not happening in my circuit. In the attached picture, node 8 is the voltage on the threshold pin, and node 10 is the output voltage before the resistor. As you can see, the threshold voltage gets to about 9.5 volts, but the output voltage remains high until the trigger voltage goes high.

The control pin is at 1.6 volts, and the trigger pin is at 0V.

Could anyone tell me if there's something else in the circuit that's keeping the output high? Or if the problem could be the spice model supplied by LT?

Have a look at this link,
http://www.instructables.com/id/Simple-and-dirty-Pulse-Width-Modulation-PWM-Wi/
LTSpice simulates this OK, and it works as advertised,
Cheers,
Richard

Trigger is active low. I know, they don't tell you that, but it is.
With Trigger low, the FF is set, allowing the capacitor to charge. When Trigger finally goes high, the Threshold input is already above the 8V nominal threshold (or 1.6V if you're forcing it that low), so the output immediately goes low. LTspice isn't lying.

Thank you so much. I changed the clock pulse to one which had a very large duty cycle, and it started working perfectly as long as the control voltage wasn't too low. And now I understand these timers a little better, which will help me in the future. I appreciate your help.