On many spin coaters you can manually turn on the vacuum and test how
well it holds down a substrate before a spin. As Roger said, the
vacuum line can easily be clogged and sometimes the o-ring in the
chuck can be damaged or mis-seated. You may need to replace it.

-- Jon
--
Dr. Jon R. Fox
email: drjonfox@gmail.com
website: http://www.drfox.com
linkedin:   http://www.linkedin.com/in/drjonfox

On Wed, Sep 2, 2009 at 5:52 PM, Roger Shile wrote:
> Shut off the gas by turning the regulator clockwise 'cause righty is
> tighty.
>
> But seriously folks,
> If the vacuum pumps works and there are no leaks in the line I'd check
> for a restriction in the vacuum line.  Vacuum lines on resist spinners
> often get clogged after sucking in resist, particularly in university
> labs.
>
> Roger Shile