Bacharach Gas Pup, Instruction, Page: 36 / 44

Gas Pup
30 Instruction 55-9002
Combustibles Sensor Replacement
If the instrument cannot be calibrated in either range, the combustibles
sensor must be replaced with a new unit.
To replace the sensor (see Figure 24):
1. Remove the instrument’s bottom plate by using a
5
/
64
" Allen wrench to
remove the plate’s four corner screws. Then remove the plate and
rubber bumper to expose the instrument’s interior.
2. Remove pump connector, pressure sensor connector, and multi-pin
connector from printed circuit board, noting orientation of connectors.
3. Remove three screws from printed circuit board; then carefully pry
the board straight up from flow block. The gas sensor is the silver
cylindrical piece in the center of the circuit board.
4. Gently pull sensor from circuit board and replace with a new unit.
Make sure that the sensor is firmly seated in receptacles and bot-
tomed on circuit board.
5. Reinstall printed circuit board into flow block; taking care to properly
position the board as shown in Figure 24.
6. Replace three screws and tighten to hold board. Reattach the pump,
pressure sensor, and multi-pin connectors to the circuit board.
7. Leak check the assembly per the following section Leak Check Basics .
8. Calibrate the instrument per the previous section Calibration . Note
that if a new sensor is installed without performing a calibration, the
word “CAL” will appear when the instrument is turned on, alerting
the operator that the instrument needs to be calibrated.
Leak Check Basics
The easiest method to perform a leak check is to close off the sample inlet,
and then observe that a pump failure occurs. For example, to close off the
standard 10" probe, either grip its end tightly with your hand, or cover
with masking tape. Note that attempting to close off the fitting ends may
be not be successful, as there are leak paths when the hose is not in place.
Maintenance