990 CLD Autoline™ Leak Detector
4-20
DRAFT 2/2/04
Station Fails to Pump Down While Displaying Gross Vacuum Failures
1. Verify that the fixture is completely closed.
2. Verify that the O-ring on the fixture is not damaged.
3. Verify that the fixture vacuum gauge is working.
❑
Verify that the vacuum gauge cable connected.
❑
Check for continuity between all four pins of this tube.
❑
If any pin is open-circuited, replace the thermocouple gauge tube.
❑
If the vacuum gauge controller is new, make sure that shorting bars and other
preparation-related items have been performed.
4. Verify that the fixture manifold is not plugged with a product or component.
5. Verify that no filters are plugged.
6. Check for leaks:
❑
A partial pumpdown indicates a large leak in the system.
❑
Continued gurgling indicates a very large leak in the system, such as a partially-open
fixture, or a disconnected or broken valve.
There is an unusually High Number of Rejects
These types of problems are the most typical found in any helium leak detection system.
While high levels of rejects can be traced to problems in the test equipment, they are also
often real leaks in the product. Before tearing down the test station, take steps to ensure that
the problem is not a real production problem. The first step in this process is to use a
challenge leak
. This is a standard leak shaped like the production part that can be inserted
into the production line to function like a
bad
part. If the station reads the leak within its
stated tolerances and within the actual production cycle, then the problem is not in the
station but probably in the parts. If the standard leak is read substantially out of tolerance,
then the problem is most likely in the station.
See “Helium Background Management” on page 6-5.
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