I have although instead of a battery I used a 12V regulated power supply. I must admit that it was a bit nerve wracking. I feared an immanent meltdown but in the end it worked fine. I believe the duration was in lower end of that listed.

The results were an improvement but not a complete recovery. Maybe a longer zap would improve things even more but I didn't want to push it.

Let us know how well it works for you.

I've rejuvenated dozens of displays using this technique. Works well. Some recommend using 6.3 VAC versus 9 to 12 VDC.
Have never tried 6.3 VAC but I have several displays that I will try it on.

This is NOT for LED displays.
This is for old style numeric displays made and used in the dark ages before LEDs were bright enough to use as displays.

L.E.D. = Light Emitting Diode
Gottlieb System 1 and 80 used florescent gas displays. The 9v battery heats up the filament wires inside the tube and burns off a layer of ash, corrosion and oxidation which makes it fire off the gas brighter again... for a while

any long term problems ?

You will have to re-brighten them about every year to 1 1/2yr on average.

Eventually the filaments become too thin and just blow open. Then you've got a dead display. Rejuventaing them does tend to shorten their life a wee bit.

Either will work fine. The trick is to watch the filaments. Leave the battery on till you see them glow red. If you see it glow orange, yellow, or white then you're leaving it connected way too long and getting to the burn out stage. Get 'er to red and then disconnect the battery immediately. Takes a few seconds only.

Some very nice info - thanks for sharing guys