I've made a 32kHz crystal oscillator using the CD4060B IC. The IC is powered by a 7805 voltage regulator which in turn is connected to a 12V SMPS.
I've probed the Q5 output (~1024Hz) using an optocoupled MSP432 and had the following waveform:
The large "off" period grows larger and eventually the oscillations stop.
I've noticed that when I placed my finger at the body of the 7805, I had stable 1024Hz oscillations for some seconds, then the "off" period started growing again until the wave collapsed. I thought it could be an overheating problem, so I added a heatsink to the 7805 and probed the current using a multimeter - still had the same result (the current drawn was at most 1.1mA).
Then I've placed much larger decoupling capacitors (220uF and 470uF) - still had the same results.
Then I connected the IC directly to the 12V SMPS and had the same result...
I also tried the original circuit, but with different feedback capacitors and resistor at the crystal filter (15pF, 33pF, 56pF, and 3.3Mohm) - still no improvement...
Finally I've powered the IC directly using the 5V pin from MSP432 and probed using the same optocoupled circuit. Then I had a stable and perfect ~1024Hz square wave.
Could this be a problem with my SMPS or is it a problem with the circuit? What could possibly indicate the fact that my finger at the body of 7805 created a "temporary stable" square wave? Why does it work with the MSP432 as the power source?
Thanks in advance.