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 S-Cubed PO Box 365 9 Mars Ct. Montville, NJ 07039 phone 973-263-0640 ex 35 fax 973-263-8888 -----Original Message----- From: mems-talk-bounces+garyh=s-cubed.com@memsnet.org [mailto:mems-talk-bounces+garyh=s-cubed.com@memsnet.org]On Behalf Of Brad Cantos Sent: Thursday, December 09, 2010 2:30 PM To: General MEMS discussion Subject: Re: [mems-talk] spin coater vacuum path Jia, I'm not familiar with this particular Laurel unit, but most spinners have a vacuum interlock switch that prevents spinning if there is insufficient vacuum at the chuck. This can often get stuck if photoresist gets down the shaft. If your switch is making partial contact, it could explain some of the symptoms that you are seeing. I would look for this interlock switch and clean it just as you did the solenoid. Brad Cantos brad.cantos@holage.com http://holage.com