How does a preamp die from sitting unused for a few months?

If the rectifier tube is burned out would the rest of the tubes and power indicator light light up, or would all electricity be stopped at the first tube (here I'm assuming the rectifier is the first tube)?

@audiodwebe In a word, no.

The tubes are not lighting up because there's no power. So the fuse (which can blow due to current inrush of the filter caps in the power supply, which can be quite a lot higher if the unit has been stored for a while). The second most likely reason is its not plugged in properly.

Old caps and moisture.  Bringing the gear in from the cold, and starting it up immediately without a chance to dehumidify would do it.

Another possibility, related to moisture is salt air. 

+1 @builder3 

invest in a variac and wake up slumbering gear correctly

Thanks, all.

The pre is only a few years old (not sure exact date as I’m currently at work) and it was just kept in my spare bedroom which I use for storage.

I’m the only one who handles the gear so no drops, bumps, etc.  And no dramatic change in temp.

Plan to look at the pre again this evening.