I've just rebuilt my pump after 2 1/2 years use, just recently couldn't maintain pressure
above 250 Psi.
Found it very easy to do. There are 37 parts in total in the kits, various washers and seals,
new plunger piston and guides. Eccentric cam is another kit.
Get yourself a clean surface to work on, dismantle one side of the pump first, paying attention to
where everything comes from, rebuild in reverse order. It's not difficult.
When i switched on after the rebuild i couldn't believe how quite the pump was, it's barely audible
above the vac' motors.
Amtech recommend rebuilding at 500 hours, but mine must have done in excess of 2000 hours.
Found the problem was the poppet valves scaled up, normal descaling only works with the pump running all the time
as when not running the valves are shut.
http://www.pumptec.com/PDFs/schematics/205V-FINAL.pdf