Thermo Scientific SAM12, Manual

Page: 163 / 176

Issue: 1.0 Maintenance and Trouble Shooting
Thermo Fisher Scientific SAM12 User Manual 11-15
and should be replaced as defined in FHT681 cards -
Removal and Replacement (page 11-6) .
3. If the fault remains with the original HV/Amplifier
channel, the fault is in the HV & Amplifier PCB and
this should be replaced as defined in
FHT681 cards -
Removal and Replacement (page 11-6) .
This condition occurs when the Background activity prevents
the SAM12 from discriminating the pre-set alarm level with the
required confidence within the Maximum Monitoring Time
allowed (see
Params 1 (page 5-8) ). Enter a valid password and
proceed as follows:
1. Select Setup|Params 2 and check the Maximum
Monitoring Time is set to a reasonable value. Adjust it
upward if necessary.
2. Select Setup|Alarms and check the Normal Alarm level
is set to a reasonable value. Adjust it upward if
necessary.
3. Select Setup|Params 2 and check the Probability of
False Alarm is set to a reasonable value. Reduce it if
necessary.
4. Select Setup|Params 2 and check the Probability of
Detection is set to a reasonable value. Reduce it if
necessary.
5. Select Calibration|HV Scan and check the High Voltage
settings of ALL six detector channels are correct.
6. Select Setup|Params 2 and set a 10 second Minimum
Monitoring Time. Check the counts in all four detector
channels are reasonable for the expected ambient
background level using Diagnostics|Detector Bars.
7. If a single channel shows a background count
significantly greater than the other detectors, a noisy
channel or a light leak is likely. Proceed as follows:
•
Swap the faulty detector MHV connection from the
relevant HV/Amplifier to that of a working channel.
Perform a further 10 second count and note the
counts in each channel.
(N.B. Bear in mind the
different operating voltages).
•
If the fault moves with the detector into a previously
working channel, the fault is in the detector
assembly and should be replaced as defined in
Removal (page 11-9) .
8. If the fault remains with the original HV/Amplifier
channel, the fault is in the HV and Amplifier PCB and
this should be replaced as defined in
FHT681 cards -
Will Not Run & Displays
“Out Of Service – High
Background Conditions”