Plans to build a CRT brightener?

[Airedale]

I've seen a few people talk about creating their own brightener, but haven't seen any plans for how they actually work.

It's just about increasing the filament voltage by about half, right?

Another mentioned you had to also increase the voltage to Grid 1.

I was gifted a VERY tired '89 RCA XL100 20". Even after adjusting the settings it is still rather dim. I figured that since this is pretty much garbage that I could experiment with it. If it blows, burns out, who cares?

If you know where to find the circuit design I'd be very appreciative.