Date: Thu, 10 Sep 2015 18:36:10 +0000
Hi all,
As always thanks to the AMMRLers who responded - it all seems to be working now!
Steve Bai at Delaware said that he had this problem for a long time and in the end just ended up upgrading (replacing?) his unit entirely since they were on a Bruker full service contract.
Martha Morton at Nebraska-Lincoln, Andy at PPG, Tim Claridge at Oxford, Lorna Murray at Edinburgh and Ralph Adams at Manchester all reported the following fix...so thank you!
The errors were to do with a dirty sensor on the top of the BST (terrible picture attached of the approximate locations). This is not in the BST manual (Z31123) or the SampleXpress user (Z13900) or technical manuals (Z13901). We'd had the unit installed for about 2 years before the problem surfaced.
On the left about 4 cm down is a small (~2 mm?) hole that you can barely fit a cotton bud soaked in isopropanol into. If you use a (plastic) dentists mirror and a torch it does look like there is some sort of lens at the end. I had to cut a cotton-bud short to get it down the bore to reach it. There is a second sensor on the left that is a little higher, larger and nearer the surface of the BST so is far easier to access for cleaning. The air hose that normally feeds the BST lift air is also convenient for thoroughly drying the sensors when you're done.
To give enough clearance for the drop-off plate we have the 50 mm extension column installed, which in my case meant I couldn't satisfactorily get at the sensors to clean them. To remove this you have to disconnect all the connections and remove the SampleXpress unit almost entirely from the top. It may be that cleaning the small sensor was irrelevant and I wasted my time, since you might be able to get at the larger sensor without disassembling the SampleXpress.
Ralph Adams at Manchester now routinely cleans the cassettes with compressed air (away from the magnets) in an effort to control the ingress of dust. Martha Morton also suggested the enforced use of Kimwipes by users for similar reasons.
Thanks again!
Geoff
(image/jpeg attachment: BST_sensors.jpg)