LI-840 CO
2
/H
2
O Analyzer
The LI-840 source and detector housings are located on opposite ends of the optical bench, and can be easily replaced should the need
arise. Follow these steps to replace the source and/or detector in the LI-840:
1.
Turn the LI-840 off. Loosen the six screws on the LI-840 top panel and remove the cover.
2.
Unscrew the tube retaining nuts on the inner air port fittings. Remove the tubing from the air port(s). Leave the tubing connected
to the source and/or detector housings; the old housing and tubing will be discarded.
3.
There are ribbon cables (below) connected to the circuit boards on the source and detector housings. Pull straight out on the
connector that is attached to each ribbon cable. The other end of the ribbon cable can remain attached to the main circuit board.
The optical bench can now be lifted away from the foam casing.
Source
Detector
Air In
Air Out
PCB
PCB
Optical Bench
Hose Barb
Bev-a-line Tubing
Ribbon Cable
Connector
4.
There are four screws on the source and detector circuit boards that must be removed. Remove the four screws in the corners of
the board, as shown below (they are slightly larger than the other four screws). Do not remove the remaining four screws.
Remove these
4 screws
5.
The source and/or detector housing (with attached circuit board and tubing) can now be removed and discarded. The bench will
appear as shown below. Be careful not to lose the O-ring on either end of the bench.
O-ring
Top View
End View
LI-840 CO
2
/H
2
O Analyzer
Source/Detector Replacement Instructions
(over)
