Ian, If I understand your schematic which gives me the idea , inspite of many polarity errors,
the trigger, as I read is Vcc/3 on pin2 , yet C5/C6 are equal so the pulse starts at Vcc and gets divided in half and never reaches Vcc/3
So C5 must be much smaller than C6. Make C6 bigger or C5 smaller.
the trigger, as I read is Vcc/3 on pin2 , yet C5/C6 are equal so the pulse starts at Vcc and gets divided in half and never reaches Vcc/3
So C5 must be much smaller than C6. Make C6 bigger or C5 smaller.