When a turbo molecular pump will not reach speed, trips out, runs hot or starts to sound wrong, the first clue is usually on the controller. It watches rotor speed, temperature and supply voltage while the pump runs, and it warns or stops the pump when one drifts out of bounds. The steps below start with what the controller reports, then check what feeds the pump.
Safety first
A turbo rotor can spin at tens of thousands of rpm, and the controller runs on mains voltage. Stop the pump, wait for the rotor to stop, then cut the mains power before you touch a cable or a flange. A pump can run up again by itself when power returns or a fault is cleared. Follow the manufacturer's manual for your model.
1. Read the code
Write down the error or warning code and what the pump was doing when it appeared. Look it up in the controller's manual: its error table names the likely causes and what to check. Our example here is Pfeiffer's TC 400 manual: an error stops the pump, a warning does not. So act on a warning early. Reset a fault only after the rotor has stopped.
2. Check the power
Confirm the mains voltage matches the controller's rating and that the right power supply feeds it. In the TC 400 error table, the wrong power supply or the wrong mains voltage causes an excess-voltage error, and a mains failure or an undersized supply causes an undervoltage warning. If the building had a voltage dip or an outage, note it: it may explain the trip.
3. Check the cables
With the power off and the rotor stopped, check the cable between controller and pump at both ends, then any remote or interlock plug and the ground. Look for bent pins, a loose connector or a crushed cable. A faulty pump connection has its own code in the TC 400 manual.
4. Check the cooling
Turbo pumps are cooled by a fan or by water. Make sure the fan turns and its vents are clear, or that cooling water flows at the rate and temperature the manual asks for. In the TC 400 error table, several excess-temperature codes share one cause: insufficient cooling. A controller that runs hot may cut drive power and speed before it shuts the pump down.
5. Check the vacuum conditions
A turbo pump comes up to speed only once the backing pump has reached the fore-vacuum the turbo needs. If the turbo never reaches full speed, or trips on run-up time, check the backing pump first. Then look for a leak, an open valve or more gas than the turbo is rated for. Vent the way the manual describes: a pressure rise that is too fast, from venting or a sudden leak, can itself cause a fault.
6. Listen and feel
A new noise, a grinding sound, or vibration you can feel through the frame is a reason to stop, not to reset and try again. The TC 400 error table lists impacts, vibration and rotor imbalance among the causes of a fault. Shut the pump down, let it stop, and leave it off.
When the checks come up clean
If the fault comes back after these checks, or the manual's remedy is to call service, the problem is inside the pump or the controller. Write down the code, the model and what you already checked. Whoever takes the unit will ask for all three.