mostly the power on delay circuits are based on the value of the polar
capacitor & resistors used in it use a variable instead any of the resistor
you think can work & try the circuit

 

These posts were also tacked onto a quite old thread - http://forum.allaboutcircuits.com/showthread.php?t=6106.

This is why we discourage hijacking existing threads. It is confusing, and many posters get no replies when they simply post onto an old thread.