Thermo Scientific SGD-O, Руководство пользователя

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Troubleshooting & Service
The FSU Pre-Amp Board
Thermo Fisher Scientific SGD-O User Guide
9-7
Measure -12V supply voltage (negative lead to ground) at negative (-)
end of C3:
-12V voltage: Should be between -11.0 V and -13.0 V.
Check the high voltage drive on U3B. Measure U3, pin 7:
U3 voltage, pin 7: Should be between 0.0 V and 7.0 V.
3. Verify the pre-amp has been zeroed. To do this, connect a jumper from
the center conductor of the coaxial cable to test point 6, and measure
the voltage at test point 6. Using R28, set this voltage to -80 mV.
Measure the voltage on test point 1. Using R1, set this voltage to +5
mV.
4. Remove the jumper and verify that test point 1 stays near zero with no
radiation on the detector. Test point 6 will ramp down from
approxi7 volts to -10 volts and reset. The speed of the ramp is
proportional to the amount of radiation on the detector. With no
radiation, this voltage moves very slowly.
If no radiation is available, you can inject a current into the pre-amp
using a large resistor in series with the +15 volt supply.
●
For boards that have the gain chip U2 (LF13006N), install jumpers
W3 and W4.
●
For boards without the gain chip, install jumper W1.
Connect a 4.7 x 10
9
ohm resistor from the +15 volt supply to the pre-amp
input terminal.
Measure reset pulse widths with an oscilloscope:
T1 (at TP4): Should be between 25 ms and 65 ms.
T2 (at TP3): Should be between (T1+14 ms) and (T1+37 ms).
T3 (at TP2): Should be between (T1+14 ms) and (T1+37 ms) (this is a
negative pulse).
Remove the 4.7 x 10
9
ohm resistor.
Reset Pulse Width
Tests