I constructed a 555 timer, LM555CN, on a breadboard to generate 1Hz, 50% duty cycle, 9VDC supply, R1 4.7K, R2 150K, C1 4.7uF, using a standard wiring diagram. Nothing unusual. It worked just great. Soldered a duplicate and tested it with 9V. Worked great. Applied 12VDC to each units as a test before continuing with the rest of the circuit and the resulting frequency went from 1Hz (with 9V) to 4KHz (with 12V). I have read that a few people have had this problem but have not found a definitive solution. Any help on this would be appreciated.