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how exactly should these look when turned on?

when i turn it on, it starts off with a yellow light, like a regular bulb, then eventually its just white like a fluorescent. its still provides some heat i guess, but is that right?

i have it facing down vertically and it's an 100w bulb in a lamp that can handle up to 200w.

I don't use mine everyday, so I don't recall the color, but it does take a few minutes to warm up and cool down.

I've been using a MVB for a little under a year now. Mine does the same thing (starts out dimmer/more yellow and brightens/gets whiter up after a few minutes) I have not had any problems with it, I assume it's normal!

yellowish turning to white sounds right to me. the color change is the change from cooler filament light to the brighter mercury vapor. no worries.

Mine starts out yellow, then goes to a more greenish white tint. MVBs that don't make that change either aren't working correctly or are too old (I have one that's 5 years old that does this).