Yes, the Towers are 6.3V.....The only bulb that lights the entire cooling tower are Op-Max, from Comet.
(I made them for GI, and internal plastic lighting)

I also removed the black rubber grommet on top and replaced with clear to complete.

Art

(Werent the 12V flashers Dim in there?)

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Thats also a 6.3V Bulb, I think a #555 Wedge.....Same thing, an Op-max fills the whole head evenly.

Nothing wrong with a Standard 5050, although the light goes only a bit more than half way up the tower, Twin 2835, 3/4 of tower,
and 95%+ an Op-Max.

I did see and help on one Simpsons game where the cooling tower plastics themselves felt/looked like a thinner plastic from mold.
If so, Id imagine a less bright bulb would look better and support more of what PinballBJB has shared.

Hmmm. maybe its 12V, of which there is a 12V opmax.

Try your 12V tower in there...I was thinking 6.3V because it stays lit, as opposed to flashing, but they may have run a 12V line.
Too hard to take the glass off on mine, but maybe someone else knows/remembers......

Please share pics of the results!