LI-COR LAI-2050 Guide

LAI-2050 Log Switch Assembly
Replacement Instructions for the LAI-2000 Plant Canopy Analyzer
1
4
Loosen the 4 hex
head screws; you
will need to pivot
the optical sensor
head to access all
of the screws.
The following document describes the procedure for
replacing the log switch assembly on the LAI-2000
optical sensor head (p/n 2000-906). Please note that
the replacement kit does not include some required
adhesives; you can search for local suppliers and/or
order adhesives at the web addresses shown below.
Note, too, that the optical sensor head is a static-
sensitive device, and precautions (e.g. a static wrist
strap) should be taken before beginning this proce-
dure.
Tools Required:
3/32” hex wrench
1/4” open end wrench
Needle nose and lock-joint pliers
Flat blade screwdriver
Adhesives, including Loctite 242 Threadlocker and
Loctite PRISM 401 (www.loctite.com), and Dow
Corning 732 Multi-purpose sealant
(www.dowcorning.com)
Time Required: Approximately 30 minutes
●Follow these steps to replace the log switch as-
sembly:
1. Use the 3/32” hex wrench to loosen the 4 hex
head screws at the connection between the
handle and the optical sensor (Figure 1). You will
need to pivot the sensor head to access the
screws.
2. Use a pair of needle nose pliers to gently pull out
the detector connector from the circuit board
(Figure 2).
3. Use the 3/32” hex wrench to remove the 4 hex
head screws at the opposite end of the handle,
where it attaches to the cable assembly (Figure 3).
Slide the circuit board out until you can unplug
the cable assembly by pulling the connector
straight out from the circuit board. Continue to
slide the circuit board out until you can access the
4-pin (white) log button/grounding connector
(Figure 4). Unplug the 4-pin connector, and slide
the circuit board back into the handle.
3
Remove the 4 hex
head screws at
the handle/cable
assembly.
2
Unplug the
detector connector
by pulling straight
out.
Slide the circuit
board out until you
can unplug the
white 4-pin
connector, and
then slide the
board back into the
handle.

5
4. Slide the circuit board out the end of the handle,
nearest the optical sensor end (Figure 5). Use the
flat blade screwdriver to pry up the log button cap
(Figure 6). Use your fingers, or a pair of pliers to
unscrew the log switch collar; wrap the collar
with tape or a tissue to prevent the collar from
getting scratched, if desired.
5. Use the flat blade screwdriver to remove the log
switch ground lug (Figure 6). You may need to
hold the nut inside the handle to remove the
screw. Remove the switch assembly (Figure 7).
Note: The log switch has a small o-ring that may
adhere to the inside of the handle; if it does,
simply use the screwdriver to pry it loose.
6. Clean any RTV residue from the ends of the
handle, and the caps that mate to the handle tube
(Figure 8).
Slide the circuit
board out of the
handle, at the end
opposite the log
switch.
6
Pry up the log
button cap...
and then remove
the log switch
collar.
Remove the log
switch ground lug.
Log Switch
Button
Grounding Lug
Connector
7
Remove the log
switch assembly.
8
Clean any residue
from each end of
the handle and the
caps that mate to
the handle.

Reassembly
1. Apply a small bead of Loctite 242 to the threads of
the new switch. Make sure the Loctite is only on
the threads of the switch; clean any excess from
the log button if present to prevent it from sticking.
2. Hold the handle so the log switch hole is facing
downward. Straighten the wires on the log switch
and grasp the wires near the connector. Insert the
log switch into the handle so that the switch
“falls” through the hole (Figure 1). Use a long
handled screwdriver to press on the bottom of the
switch to hold it in place while you tighten the
collar over the switch. Do not overtighten the
collar, as the switch body can be damaged; hand-
tighten only enough to compress the o-ring on the
switch.
3. Attach the ground lug. You may need to hold the
nut inside the handle with the pliers or 1/4” open
end wrench as you tighten the screw (Figure 2).
4. Insert the circuit board into the handle from the
end opposite the log switch (Figure 3); the leading
edge of the board has the 16-pin connector that
attaches to the cable assembly, and the board
components face the same direction as the log
switch. Slide the board through the handle so that
it extends through the opposite end, far enough so
that you can attach the 4-pin log button/grounding
connector.
5. Apply a bead of 732RTV to the end of the handle
at which the cable attaches. Attach the cable
assembly to the circuit board connector (Figure 4),
slide the circuit board into the handle, and attach
the 4 hex screws (Figure 5).
1
Hold the handle
upside down so the
log switch can fall
into place. Hand
tighten the collar
over the log switch
button.
2
Attach the ground
lug. Hold the nut
inside the handle
and tighten the
screw.
3
Slide the circuit
board back into the
handle.
4
Reattach the 4-pin
grounding connec-
tor and the cable
assembly connec-
tor to the circuit
board.

LI-COR, inc. ●Environmental ●4421 Superior Street ●P.O. Box 4425 ●Lincoln, Nebraska 68504 USA
Phone: [phone] ●FAX: [phone]
Toll-free 1-800-447-3576 (U.S. & Canada)
[e-mail] ●www.licor.com PCA-105
®
5
Attach the cable
assembly to the
handle with the 4
hex head screws.
6. Plug the sensor head detector connector into the
circuit board (Figure 6). Make sure all pins are
inserted into the connector. Apply a bead of
732RTV to the end of the handle (Figure 7). At-
tach the optical sensor to the handle using the 4
hex screws; note the orientation of the handle and
log switch in relation to the sensor head (Figure 9).
7. Apply a small drop of Loctite 401 to the top of the
switch and install the button cap (Figure 8); be
careful not to apply too much adhesive, as excess
adhesive will lock the switch in place.
6
Plug the sensor
head connector
into the circuit
board.
7
Apply a bead of
732RTV to the
end of the handle.
Attach the sensor
head to the handle
with the 4 hex
head screws.
8
Apply a small drop
of Loctite 401 to
the top of the
switch and install
the log button cap.
9
Note orientation of
sensor head and
handle.