Hello, and Happy New Year !
There are4 a couple of issues whcih need to be got around to enable the 16F690 driver IC drive IV-4/IV-17's
The VFD tubes have two segments more than the B7971, and you might notice that there is a lack of outputs on the pic16F690 used on the Smartsockets.
Also, the VFD's require a voltage source for each segment, where the B7971 needs a voltage sink. Yoiu could lose all of the transistors and inste3ad connect the 16F690 to the VFD IV-4/IV-17 via one of the many vfd driver IC's. This might be a bit expensive because the VFD drivers aren't cheap, but it would work for sure.
I can't remember the exact IC which could drive the VFD, but they have voltage source outputs, arranged one-for-one with the inputs. Perhaps the most common VFD drivers I have come across have been shift register based, but the 16F690 driver has no facility to drive shift regs at the moment.
Having said that, I was working on a 4 x IV-4 display using two VFD drivers controlled by a pic at the middle of last year whilst trying to make a 4 tube display which worked as if it were 4 Smartsockets connected together. I seem to remember there being issues regarding the refresh rate. Maybe I should look at that again only this time try controlling only two tubes from one controller. The minimum requirements for a 2 tube display would then be a PIC, a VFD control chip and a PCB (plus power supplies). I suppose it could end up being very small and neat.
Seasonal Wishes to Everyone !