Model 990 dCLD II Component Leak Detector
6-3
6.2.2 HIGH VAC LED does not Light
To check the HIGH VAC LED:
1. Verify that the backing pump is powered, running, and producing a forepressure less
than 1 Torr.
NOTE
The 990 dCLD II will not start any turbo pump until the
forepressure is less than 1 Torr.
If the forepressure is less than 1 Torr and the turbo pump has not started:
a. Determine and correct the cause of high forepressure.
b. Turn the control unit off for a period of at least 10 seconds.
c. Turn the control unit back on.
If the turbo still does not start:
2. Check for a disconnected or damaged turbo pump cable.
3. Check for a disconnected or damaged main spec tube block connector cable.
4. Was a new pump installed? Allow up to 45 minutes for a newly-installed pump to reach
full speed (the HIGH VAC LED is lit).
5. If the LED fails to light, replace the 990 dCLD II control unit to determine if it is at fault.
6. Replace the pump if a new control unit doesn't solve the problem.
If HIGH VAC LED still won’t light, call Varian Customer Service at 1-800-8VARIAN
(1-800-882-7426).
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