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SGD-O User Guide
Caution The C13 capacitor is located under the metal shield on the FSU
pre-amp board. Everything under this shield is high impedance circuitry.
Do not touch anything under the shield with bare hands! If any of these
components are contaminated, the detector signal will fluctuate, making
the detector ineffective. Use only clean metal tools to touch these
components. Do not apply any kind of cleaner to them.
1. Check the FSU detector power supply voltages.
There are + 15 and - 15 volt supplies on the pre-amp board coming
from the power supply in the panel. Test points are provided for both
supplies near J2. The ground test point is near J1. R10 and R11 on the
pre-amp are 10-ohm resistors that are in series with the -15 and +15
volt supplies.
The voltage drops across these two resistors are listed below. There is
also a +12 volt regulator on the pre-amp board. This voltage can be
checked on the positive side of C21.
Measure + 15V and - 15V supply current tap voltages:
+15V: Voltage drop across R11 should be between 80 mV and 220 mV.
-15V: Voltage drop across R10 should be between 40 mV and 150 mV.
Measure +12V at positive (+) side of C21:
+12V voltage: Should be between 11.0 V and 13.0 V.
2. Check the high voltage on the power supply board. It should be
between 1300 Vdc and 1600 Vdc. This voltage can be measured on the
ion chamber.
There are +15 and - 15 volt supplies on the high voltage power supply
board coming from the power supply in the panel. R1 and R3 on the
high voltage power supply board are 10-ohm resistors that are in series
with the -15 and +15 volt supplies.
The voltage drops across these two resistors are listed below. There is a
-12 volt regulator on the power supply board. This voltage can be
checked on the negative side of C3. The ground point is on the
bottom end of CR3 nearest U3.
Measure +15V and -15V supply current tap voltages:
+15V current: Voltage drop across R1 should be between 130 mV
and 280 mV.
-15V current: Voltage drop across R3 should be between 130 mV
and 280 mV.
Thermo Fisher Scientific
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