I am an undergraduate student in search of help troubleshooting a Varian HPLC system. I am finishing my last semester for a Chemistry B.S. Our University has a Varian HPLC system with PDA (UV/Vis) and MS detection that was set up in 2006 and last serviced in 2008. The system is comprised of two Varian 212 -LC chromatography pumps, a Varian ProStar autosampler model 430, a Varian ProStar model 335 UV/VIS detector equipped with a photodiode array, and a Varian 500 MS. Unfortunately the university has not been consistent with running and maintaining the above instruments. When we began working with the system much of it was apart and non operational, we have achieved a working condition on the two Varian 212 -LC chromatography pumps, a Varian ProStar autosampler model 430, a Varian ProStar model 335 UV/VIS detector equipped with a photodiode array. We have been running samples of Caffeine to test the system and construct a calibration curve. Due to our believed success with those instruments, we are now shifting our attention to troubleshooting and restoring the Varian 500 MS to a working condition. I would be very grateful for any tips or help you can share on any of the instruments in the system. The main problem we have currently reached is the forward turbo pump inside the Varian 500 MS is not turning on. The associated fan is not running either. The rear turbo pump is running and the computer provides its statistics in the diagnostic tab. We are running Varian WorkStation software 6.9.2. Have you experienced this issue before, or anything similar? We are also in hope of tips for the use of the rotary vane HS625 pumps.