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Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 302
12.7.13. PMT PREAMPLIFIER BOARD
To check the correct operation of the preamplifier board, perform an the optics test (OTEST) and an
electrical test (ETEST) described in Sections 12.7.12.1 and 12.7.12.2 above.
If the instrument passes the OTEST but fails the ETEST, the preamplifier board may be faulty or
need a hardware calibration.
12.7.13.1. High Voltage Power Supply
The HVPS is located in the interior of the sensor module and is plugged into the PMT tube. It requires 2
voltage inputs.
The first is +15 V, which powers the supply.
The second is the programming voltage which is generated on the preamplifier board.
Adjustment of the HVPS is covered in the factory calibration procedure in Section 12.8.4.
This power supply has 10 independent power supply steps, one to each pin of the PMT. The following
test procedure below allows you to test each step.
1. Turn off the instrument.
2. Remove the cover and disconnect the 2 connectors at the front of the NOX sensor
module.
3. Remove the end cap from the sensor (4 screws).
4. Remove the HVPS/PMT assembly from the cold block inside the sensor (2 plastic
screws).
5. Disconnect the PMT from the HVPS.
6. Re-connect the 7 pin connector to the sensor end cap, and power-up the
instrument.
7. Scroll the front panel display to the HVPS test parameter.
8. Divide the displayed HVPS voltage by 10 and test the pairs of connector points as
shown in the figure below.
9. Check the overall voltage (should be equal to the HVPS value displayed on the front
panel and the voltages between each pair of pins of the supply
EXAMPLE
If the HVPS signal is 700 V the pin-to-pin voltages should be 70 V.