Are you Going to change the 8038 frequency by changing the capacitors??
No Way!!
Timing Capacitor Only determine the frequency range!!
USE A POT TO CHANGE THE FREQUENCY!
take a look at this simple 8038 generator:
The Basic characteristics of the circuit with a few components. By have VR1-potentiometer, R1-resistors and C1-capacitors are determined frequency output. Which has formula to calculate the frequency output as follows.
The Frequency output (f)
= 0.15/(VR1+R1)C1
Changing Frequency by turning the VR1 pot!
Another 8038 Generator:
The frequency of the output wave form can be adjusted using R7 .It must be a 100K Log POT.
Another One:
The IC contains an internal square wave oscillator, the frequency of which is controlled by timing capacitors C1 - C4 and the
10k potentiometer!