Commenting further on this, we just had our red diode laser replaced (because the shape of the pulse was out of spec). We have had numerous problems in the past with Time Delay, at least in part due to fluidics (see prior threads). In any case, within only several days, we started to have problems again: loss of sensitivity, high compensation, and failure to calibrate. This was in fact caused by the laser drifting out of alignment. I wonder if we are seeing a new generation of unanticipated problems with the new lasers (cooled type) that are designed to fix the prior reliability problem. I'd appreciate it if others with the new laser would report their experiences here so we can keep track of the issue. Mark Shlomchik, MD, PhD Associate Professor of Laboratory Medicine and Immunobiology Yale University School of Medicine >James, > >Whereas the problems you see could certainly be due to bad luck with >the diode lasers, it is also possible that the mount for the red >laser is giving you problems. We have noticed that the extra weight >of the new TEC diode laser makes it more vulnerable to becoming >misaligned, resulting in loss of signal and in loss of ability to >compensate because the timing of FL4 pulse is out of the time delay >calibration window. To distinguish the new possibilities, you (or >your service rep) can measure the output of the laser (if lower than >specifications, obviously it needs replacement); if the power is OK, >then check time delay calibration. If time delay fails and the PMT >voltage required to meet the target channel is higher than normal, >the laser alignment may have drifted. Time delay calibration is a >sensitive measurement of how the instrument is functioning, and even >a small misalignment of the laser will prevent it from passing. > >Kevin > > > > > >Kevin L. Holmes, Ph.D. > >Chief, Flow Cytometry Section > >Research Technologies Branch > >Bldg. 7, Room 01 > >NIAID, NIH > > > > > >-----Original Message----- >From: James F. George, Ph.D. [mailto:jgeorge@uab.edu] >Sent: Monday, December 17, 2001 5:26 PM >To: Cytometry Mailing List >Subject: FACSCalibur Red Diode Laser Reliability > > > >Greetings fellow flow cytometrists > > > >We recently acquired a new dual laser facscalibur. We have had some >serious problems with the stability of the red diode laser. In two >months, the laser has been changed out three times and our fourth >service call for the same problem will commence tomorrow. >Typically, one will observe a decline in sensitivity in fluorescence >in channels that rely on the use of the diode laser, accompanied by >a large increase in the amount of compensation required for those >same fluorescence channels (I am being deliberately non-specific >here to accomodate those who do not have BD instruments, for those >facscalibur users, I am obviously talking about FL4, but this would >depend on the fluorochromes that were being used etc). I went with >BD because my previous long experience with the highly reliable >Facsscan and the fact that I really needed two lasers. >Unfortunately, the other laser is not useful if it is unreliable. > > > >Have others experienced this problem, particularly since BD switched >suppliers for the diode laser? > > > >This is making me crazy. Any info you have on this would be useful. >I am working with BD on this (upper management has been pretty >responsive), but currently I have not seen a permanent solution to >the problem. > > > >-James -- Mark Shlomchik, MD, PhD Associate Professor of Laboratory Medicine and Immunobiology Yale University School of Medicine 203-688-2089 203-688-2748 (fax) mark.shlomchik@yale.edu
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