GC-MS cannot pump down.

Open the analyzer door wide enough so that you can see the blades of the turbo pump. Turn on the power so that the rough pump starts. Do the blades spin at all? 

If they do not spin from the air motion of the rough pump, the turbo pump has failed and must be replaced.  There is not much to lose at this point so you could also use the tip of an autosampler syringe needle to try to move the blades. If the blades do not move at all, the pump has failed.

If the blades spin, at least the turbo pump is not stuck.  On a single quad system the turbo pump is turned on immediately.   If the blades spin but you can tell that they are not speeding up because of power, either the turbo pump motor has failed or the turbo pump power supply has failed.   

If the blades spin under power - close the analyzer door and open up the vent valve.  While holding the analyzer door shut the rough pump should evacuate the chamber in less than a minute and you should hear air sucking through the vent valve.  If that happens, close the vent valve.  Monitor the turbo speed.

The turbo pump motor is a stepper motor driving at 60,000 rpm.  The feedback loop of the tachometer must work or the turbo power will be turned off.  So a turbo pump failure can be shaft bearing, motor, tachometer, or power supply.

Sometimes the IDP-3 tip seals need to be replaced earlier than 12 months. Trying a different pump was good troubleshooting.

Hi Paul,

  Thank you for your quick reply.  

  We just got a chance to test following your advice. We do see turbo pump spins once MS is turned on and rough pump starts to work, it spins slowly before we close the side door, once the door is closed we can feel strong vacuum pulling and by that time we cannot see the turbo pump blade from the window (which I would say because it spins fast enough to not show the blade is still, but the speed is unknown). We still see the turbo pump speed as 0% the whole time, which tells us either the pump is not spinning fast enough to get a speed reading, or not enough power being supplied, or the speed reading device (tachometer) is not working so no matter what it only show 0%. This is what we have so far, let us know if we can do anything else to check.  Thank you!

  Best regards,

  Hill

zchen   If the turbo pumps only spins slowly from the air passing through to the rough pump but does not spin fast like it would with power, either the turbo pump motor has failed or the turbo pump power supply has failed. Please contact Agilent     Contact Us .

Thank you Paul, will do and we can update once it's checked by the Agilent. 

Have a nice one.

Best regards,

Hill

Hi Paul,

  Just a quick follow-up question:

  If we turn on the GC and MS and rough pump starts to run, when the EI side door/vent valve are still open, are we supposed to see the turbo pump blade starts to spin faster and faster or it only happens when the side door/vent valve are closed and MS is under vacuum? Our case is when the side door is open the blade seems to spin very slowly, once the door and valve are closed it spins much faster. Thank you.  

  Best regards,

  Hill

Hi Paul, 

  Just want to let you know that we identified the problem, it was the power supply unit. Since power supply is bad that's why turbo pump speed was 0% the whole time. We have replaced the power supply and MS is working now. Thank you for your patient help and tips!

  Best,

  Hill