It's been a few years since I inspected the inside of the seismometer enclosure. Recently, the seismometer output seemed to be stuck and not responding to large events, and the absolute value of the counts seemed to be too large negative. So eventually I removed the cover of the enclosure and peeked inside. Everything appeared to be corroded!

I removed all of the diet coke cans inside the enclosure that were used to increase thermal mass -- four of them were less than full. I assume that they leaked somehow and the moisture caused the corrosion. 

The rotor blade was sticking against the spacers used to separate the two stator blades. 

Most of the hardware seems unaffected, but the 4-40 bolts holding the stators are completely rusted, along with the two springs. I replaced the 4-40 bolts with brass versions that should perform better under moist circumstances. The springs were replaced after a trip to Lowes. Prices have gone up. When I first purchased the springs they were $3.50 per package of two -- now its $5.00.

I decided to replace the wooden plug that supported the stator blade with a 3D printed version. It should add more stability (in that it is not as susceptible to moisture) and could be fabricated with better tolerances. A few minutes designing with FreeCAD, coupled with an hour of printing yielded a near-perfect part.

The slot gives perfect alignment and the two screw holes will hold the stator in place better than the friction fit from the wooden piece. Here's what it looks like installed:

This is the entire seismometer, with PCB sensors, new springs and some new hardware. I wiped all of the non-stainless hardware with WD-40. It's ready to be re-installed into the enclosure and begin taking measurements again.