Thick Gasket Kit (6400-37)

The 6400-37 Thick Gasket Kit is designed to help measure photosynthesis on plants with thick, fleshy leaves, leaves with thick midribs, or cylindrical leaves. Sealing the leaf chamber around these leaves is challenging, as is preventing leaf damage. The Thick Gasket Kit doubles the thickness of the standard neoprene gasket on the bottom of the cuvette, which increases gasket flexibility. To use the Thick Gasket Kit, the hinge at the back of the chamber must be replaced, as well as replacing the gasket on the bottom leaf chamber and the addition of a thicker shim over the sensor head manifold. This kit is compatible with all versions of the LI-6400 or LI-6400XT and OPEN software.

The assembly requires a Phillips head screwdriver, and takes about 20 minutes to complete. The instrument should be powered off during this procedure.

Follow these steps to install the 6400-37 Thick Gasket Kit:

1. Disconnect the light (PAR) sensor and log switch connectors located under- neath the tripod mounting bracket. Disconnect the Light Source power cable (if installed).
2. 
2. Detach the chamber top from the handle by opening the chamber and turning the adjustment nut until it is free of the handle.
3. 
3. Remove the handle screws, which will release the handle, and set aside. The screws are located on the back side of the handle. Note that the middle screw (if there is one) is shorter than the other two.
4. 
4. Remove the two screws attaching the hinge to the sensor head manifold. Remove the upper half of the leaf chamber.
5. 
5. Remove the three screws attaching the hinge to the upper chamber manifold.
6. 
6. Remove the gasket from the lower leaf chamber and remove any gasket adhesive residue left on the sensor head with a citrus-based solvent such as Goo Gone™. Install the new thick gasket.
7. 
7. Install the new thick, three-hole shim on top of the thin shim (if installed) on the sensor head manifold. Other- wise install the new thin shim and then the thick shim on the sensor head manifold.
8. Fold the hinge completely open so that the two leaves of the hinge are 90° of each other and the spine of the hinge is inside the opening.
9. Install the new hinge with narrower tab attached to the upper chamber manifold using the screws from the original hinge.
10. Place the upper chamber manifold and hinge back on the lower sensor manifold. Install the two outer screws in the hinge, but do not tighten. This will allow for slight adjustments to ensure the other screws fit in Step 11. Be sure to install the correct screw through the bracket holding the round, black connector for the light source power (it’s slightly longer than the other one).
11. Position the fiberboard heat shield between the hinge and the handle. Install the chamber handle support bracket and reinstall the handle screws. Tighten all screws that hold the hinge in place.
12. 
12. Move the leaf temperature thermocouple upwards so it is just visible above the plane of the bottom gasket.
13. 
13. Reattach the adjustment nut and adjust it until the chamber gaskets are just touching each other when the chamber handle is closed, then open the handle and turn an additional one half to one full turn tighter.
14. 

NOTE: With the new gaskets, it is possible to overtighten the adjustment screw and damage the hinge. Do not attempt to compress the gaskets beyond the aforementioned adjustment.

Turn the instrument on and check for leaks by breathing gently around the sensor head. Perform the same leak test when a plant leaf is clamped into the chamber. If necessary, seal any leaks using a gas- impermeable removable substance such as poster tack.

Table 1‑1. 6400-37 Thick Gasket Kit.

Part Number	Description	Quantity
122-00003	4-40 1/4" screw	5
122-00009	4-40 1" screw	4
193-12469	Chamber Hinge	1
6564-029	Chamber air passage foam	2
6564-057	Handle catch rod	1
6564-156	Chamber leaf gasket (white)	3
6564-202	Fluorometer chamber gasket, round (white)	3
6564-252	Air passage spacer	1
6564-314	Thick air passage spacer	1
6564-315	Thick chamber gasket (black)	5
6564-316	Fluorometer chamber gasket, round (black)	5
9864-247	Chamber handle support clamp	1