# Difference between NE555P and 555CN?

I'm working on a circuit that uses two 555 timers. At the electronics store, they gave me a handful of 555 chips, I only noticed the difference when I finished my circuit: the R1 value is shorted out, my R2 value is 150 Ohms, and the electrolytic cap is 10 uF. (see the schematic with R3, D1 and D2 replaced with a single piezo speaker).

The thing is, if I put in the 555 chip marked LM555CN, it appears to be 'always on'. But, if I use the Texas Instruments chip marked NE555P, the circuit works as expected, that is, it generates an annoying screech on a piezo speaker. What is the difference between these two seemingly identical chips? Is it a quirk in the TI chip that it works when R1 is just shorted out? And lastly, is there a way around this problem other than me sitting at the electronics store picking out the TI chips?

Also note - the piezo speaker doesn't have any oscillator in it, that is, when you apply raw power to it, it just clicks once and sits there, that's why I have the second 555 timer, and it's not an option to change out the speakers at this point.

$$f\approx\dfrac{1.44}{(R_1+2R_2)C}$$ Note also that, during the time (even short) while that BJT is short circuiting the battery voltage, your whole circuit sees no battery voltage, so it is no wonder that you don't hear anything, or that it does strange things. In fact, the IC losing its supply probably makes it stop keeping that BJT on, so the short circuit won't last long.