Numitron clock project
The Russian IV-9 Numitron-like displays appear to require 3.5V at around 18mA per segment. That means that to mux 6 of them you'd need \$3.5 \times \sqrt 6\$ = 8.6V at about 350mA per common (17% duty cycle), ignoring drop in the drivers. 

That is more than the 7447 can handle, and much, much more than a 74HC238 can handle. 

I didn't look at the rest of the circuit. Suggest static drive using a power shift register or 74HC595 + ULN2803 buffers.