STP-301/451 Series Instruction Manual 
 
11-8
Troubleshooting 
11.2.5 Other Abnormalities 
Table 11.4  Troubleshooting While the STP Pump is Rotating
 
Symptom  Probable causes  Countermeasures  Refer to 
The STP pump stops.    Check the past errors 
referring to Section 
11.2.2, "Displaying Past 
Abnormalities/Errors and 
Accumulated Running 
Time". 
11.2.2 
Insufficient ultimate 
pressure 
Failure of the backing 
pump 
 
Check the backing pump 
for its capacity and start 
state. (use a pump with 
the recommended 
capacity or more) 
4.3.4 
13.1 
  Leakage of the piping 
system 
Check the piping system 
for leakage. 
4.3.4 
  Residual molecules  If the main composition is 
H
2 
or H
2
O, perform 
baking; if it is other than 
H
2
 or H
2
O, clean the 
inside of the vacuum 
equipment. 
5.1 
    (If gases remain inside 
the STP pump, contact 
Service office when it is 
needed to be cleaned.) 
11.3.5