From: Les Hicks <hicks@maildrop.srv.ualberta.ca>
  To  : RASMB@BBRI.HARVARD.EDU
  Date: Wed, 13 Nov 1996 16:08:47 -0700

Hello out there,

        I operate three Model E's in Cyril Kays' lab, and we are
experiencing problems keeping them running.  We are trying to locate a drive
for one of them, and haven't had any luck through Beckman.  We have pretty
well exhausted their stock of rebuilt drives trying to find one that
operates properly.  The last three that we tried either had precession or
major oil leakage problems.  Is there anyone out there with a functional
Model E that is not being used anymore?  We would be very interested in
obtaining the drive from such an instrument if there is one available somewhere.
        We have also recently had a problem obtaining a good CFE, synthetic
boundary (capillary) double-sector centerpiece from Beckman.  The first one
we received from them didn't have any filling holes machined in it.  The
next two that we received had the capillaries machined too large.   The
result is that when doing a fringe count to determine concentration,  the
solvent layers onto the protein solution almost instantaneously, producing
mixing in the boundary region.  I have compared the concentration determined
using these new centerpieces and the one remaining good one we have left,
and the concentration differed by 35-40%.   I assume that these centerpieces
are used in the new XLI instrument, so users of the XLI or Model E should
beware of this problem.  I have sent the centerpieces back to Beckman, and
they have confirmed that they are indeed being machined incorrectly,  but
aren't sure how long it will take to correct the problem.  It seems that a
lot of their expertise in analytical ultracentrifugation has been lost with
older service and technical people retiring, etc.
        The other frustrating problem we have had lately involves blurring
of the fringes in the interference optical system with new sapphire windows.
We purchased five new sapphire windows from Meller Optics (who produce the
windows for Beckman) earlier this year, and upon first trying them in sample
runs, all five windows in various combinations produced blurring of the
fringes at the cell bottom at any speeds over 18,000-20,000 rpm.  We have
seen this phenomenon in the past with old windows that over time, after many
runs, gradually start to blur. I assume this is due to some sort of
cumulative pressure effect over time.  But we have not seen this with brand
new windows before.   I have returned them to Meller, and they have examined
them to try to figure out what is causing this problem, but they can't find
any obvious defects in them.  They are going to send us replacements once
they have been made,  but I am wondering if we are going to see the same
thing again.  Has anyone else had similar problems with new sapphire
windows?  Any suggestions?


Regards,

Les Hicks
Dept. of Biochemistry
University of Alberta
Edmonton, Alberta
Canada