I took the parts out in the pathway and cleaned them so it is less likely that there is some blockage than leakage. Any good way to check the leakage? And I confirmed that the external vacuum pump and the vacuum sensor on the spin coater are all right. Thank you. Jia On Thu, Dec 9, 2010 at 2:31 PM, Gary Hillmanwrote: > Gentlemen, there are two factors possibly at work here. One is that the > vacuum passageway is blocked, the other is that it is leaking. > > Gary Hillman