Model 990 dCLD II Component Leak Detector
6-5
6.2.4 No Helium Response
6.2.4.1 Check the Helium Response Using Diagnostic Port Interface J12
To check the helium response:
1. Use ?SETUP<CR> to verify auto ranging is active. If necessary, issue the AUTO
command.
2. Check that the leak to be read is installed in the system with the valve open.
3. Is the calibrated leak broken? Has it been dropped? If it rattles when shaken, it is broken
and must be replaced.
4. Is the SPEC TUBE LED on? See Section 6.2.3 “SPEC TUBE LED does not Light or Stay
5. Is the HIGH VAC LED on? See Section 6.2.2 “HIGH VAC LED does not Light” on
6. Are the valves in the system operating correctly? Check that the valves are properly
oriented and actuating when commanded.
7. With the leak valved off, issue the ZERO command to ZERO the 990 dCLD II.
8. Enter 250 PUT-ION<CR>, 380 PUT-REPELLER, 200 PUT-FOCUS, 400 PUT EMISSION,
then ?ALL<CR>. The typical voltage readings should be as follows:
9. If all voltages are more than 20 percent
lower than the values above, or if any two
voltages are equal, disconnect the spec tube block connector and check the ion source
for shorts using an ohm meter. If the Ion Source is not shorted:
a. Replace the 990 dCLD II control unit to determine if the control unit is defective.
b. Finally, replace the turbo spec tube cable to determine if it failed.
10. If the OFFSET number is 10 or 100, the preamplifier in the spectrometer tube could be
defective. See Section 5.3.1 “Removing the Spectrometer Tube Assembly” on page 5-6,
and then Section 5.3.4 “Removing the Preamplifier” on page 5-13.
Parameter
Voltage
Parameter
Voltage
FILAMENTBIAS
099.0
FIXEDFOCUS
190.0
IONCHAMBER
242.9
SUPPRESSOR
147.0
VARIABLEFOCUS
202.4
EMISSIONCURRENT
1.110
REPELLER
388.1
OFFSET
64
GAIN
1.0
Summary of Contents for 990 dCLD II
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