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

Did you forget to water it?

DeKay (sorry Roxy)

The pre won't have died from sitting unused for a few months. It died because of something else as per carlsbad2's post. Or it could have been going to expire anyway before it was put away. If it had been put away from years and died from some caps drying out, that would be a different thing - though even that is rare enough.

Coincidence...something was on the verge.

I had an ARC SP 15 that I bought from a guy who had it in storage for years. It popped a fuse the second I turned it on. After replacement it burned up a cap that was swollen and died again. I had to re-cap the thing! Soon thereafter the switched 120v recep. on the back began heating up and failed- broken solder.

For sure the long time unused and maybe bumpity bumps in storage took it’s toll on the unit. After all that the preamp was fantastic and served me well until I bought a Ref 6 SE.

It was fun soldering and tinkering with it. That brought back fine memories of tinkering with old tube radios as a kid. Man I miss the 70s!

Depends on the storage. Anywhere unheated, or under-heated can be a problem. Things can draw moisture, which leads to corrosion.