Models 947, 948 and 960 Leak Detectors Operations and Service Manual
4-4
On-demand maintenance functions are listed in Table 4-2.
Table 4-2
As-Required Maintenance
Most Common Symptom
Refer to
Trap almost empty, nearly 14 hours without a refill.
“Liquid Nitrogen Cold Trap (Models 948/960 only)” on
page 4-10
Preamplifier failure.
“Spectrometer Tube Exchange” on page 4-21
Loss of sensitivity, increase in background, high ion
voltage (> 300 VDC), required to tune the leak
detector.
“Spectrometer Tube Overhaul” on page 4-11
Filament failure (as soon as convenient after second
filament is in use).
“Replacing the Ion Source” on page B-6
Pump running rough, vacuum not attainable.
“Rough Pump and Forepump Oil Level Check
(Oil-sealed Mechanical Pumps)” on page 4-31
TC1 gauge needs replacement as indicated by the
fact that:
❑
Test port pressure does not come down
(atmosphere indication) when start button is
pushed (test mode) assuming no leaks.
❑
Test port pressure comes down slightly
(1/4 to 1/2 scale) when test port plug is installed,
once again assuming no leaks can be heard or
seen (gross leak).
TC2 gauge needs replacement as indicated by the
fact that:
❑
Spectrometer tube pressure shows high pressure
(full scale indication). System will not activate the
ion source filament due to a false high pressure
indication, a failed turbo pump, or a leak in the
spectrometer tube.
❑
Spectrometer tube pressure comes down slightly
(1/4 to 1/2 scale) after the leak detector has been
warmed up for 30 minutes.
“TC1 and TC2 Gauge Replacement and Calibration”
on page 4-23
Unsatisfactory condition on visual inspection.
The frequency of port cleaning depends on the
application.
Summary of Contents for 948
Page 175: ......
