You can't make them brighter by cranking the voltage if anything that will damage the logic board. The VFD is equipped with a set brightness command which you can use to set the brightness of the unit, see the manual for the exact command.

Well yeah. I figured it would fry the regulator or ...

Well, I was trying to get back into doing car-puters. I bought a VFD2041 to use in my heads up display, but it's not bright enough to see when it's sunny out.

Is there any way I can physically modify it to crank the voltage? The original VFD was about 3 times brighter.