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Thermo Fisher Scientific
Preamp Cover
Detector Assy
Optical Bench
Figure 7–10. Replacing the Detector/Preamplifier Assembly
3. Remove the two screws holding the preamplifier cover to the
preamplifier assembly and remove the cover.
4. Insert an Allen wrench through the access holes in the preamplifier
printed circuit board, and remove the screws holding the detector
assembly to the optical bench. Carefully remove the detector assembly
from the optical bench.
5. Install the new detector assembly by following the previous steps in
reverse.
6. Calibrate the preamp board, and then return to Step 7 to set S/R. Refer
to the "Preamp Board Calibration" procedure that follows.
7. Set S/R as follows:
a. From the Main Menu, press
The Initial S/R Ratio screen appears.
b. At the Initial S/R Ratio screen, press
Access Holes
Preamp Board
>
to Initial S/R Ratio > and press
S/R ratio to the value of the current ratio and press to store the
value. The initial S/R ratio should be between 1.14 and 1.18.
Detector/Preamplifier Assembly Replacement
To Motor Plate
To PREAMP on Measurement
Interface Board
to scroll to Service > press
to select set the initial
Model 48i Trace Level-Enhanced Instruction Manual
Servicing
.
7-19
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Troubleshooting
