Fonik VCO 555 Thomas Henry

BUILDING NOTES

1)
in the original schematic of the VCO frmo thomas henry we three times a resistor R26, whereas R25 is missing completely.
so here are the values corresponding to the PCB labeling that are not covered correctly by the schematic/parts list:
R25 - 300k
R26 - 39k
R55 - 5.6k

2)
when powering from 12V:

3)
when you have a hard time finding a precision trimmer wit 25k, just use 50k. does the job as well.

4)
C4 is the timing cap. use a nice C0G/NP0 or a mica for better stability.

Gallery