6400-91 Peltier Kit - LI-COR Biosciences91 Peltier Cooler Installation Kit includes one Peltier...

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6400-91 Peltier Cooler Kit Continued on next page Installation Instructions for the LI-6400/LI-6400XT Portable Photosynthesis System Introduction There are two Peltier thermoelectric block coolers located on either side of the LI-6400/XT sensor head, beneath the two fans and heat sinks. The block coolers regulate the tempera- ture of the air that is circulated through the leaf chamber. The coolers can fail in one of two ways; they can fail completely, whereby there is no change in the block temperature, or they can become inefficient, and fail to modify the block tempera- ture over their specified range. In the case of total failure, one or both of the coolers are physically broken, and exhibit an open circuit condition. If the coolers function, but will not change the temperature sufficiently, the resistance of the cooler(s) is likely too high, rendering it inefficient. This document describes how to test the Peltier coolers (this requires an ohmmeter), and replace, if necessary. The 6400- 91 Peltier Cooler Installation Kit includes one Peltier cooler, and additional parts required for the repair, including: Q t y . D es cri p t i o n P a r t N o . 1 Peltier Cooler 435-04171 2 Black thermal conductor pads 108-03376 2 Shrink wrap 220-00291 Troubleshooting 1. See if the fans spin freely The LI-6400XT has circuitry that senses if the fans for the coolers are running. If the fans do not turn, power will not be applied to the coolers. Blow on the fan blades and see if they turn. If they do not spin freely, they may be jammed; dislodge the impediment, and the problem may be solved. 2. Check the fuses There are two fuses inside the LI-6400XT console, along the edge of the lowermost circuit board, labeled TEC- and TEC+ (Figure 1). Check these two fuses before proceeding. Center the fuse(s) in the clip holder to make sure it has good contact; if the sides of the clip holder are flared outward, remove the fuse and pinch the clip until it makes tight contact with the fuse. PPS-274 Figure 1. Check the fuses at TEC- and TEC+, highlighted above. 3. Test the resistance of the cooler(s) a. Turn the LI-6400XT off and let it sit, untouched, for at least one hour so that both sides of the Peltier coolers are at the same temperature. b. Remove the three screws that secure the bottom cover of the sensor head IRGA (Figure 2). You may have to pry the back end of the cover, and lift it enough to clear the log button and light sensor connectors on the side. c. Follow the red and black wires from the coolers, and locate the two 4-pin white connectors on the edge of Note, too, that in addition to these instructions, a video showing how to replace the coolers is available at: http://www.licor.com/6400cooler-replacement T o o ls r e q uir e d: Ohmmeter 5/64” hex key (allen wrench) Wire cutter/stripper Soldering iron and solder Philips head screwdriver Tweezers Heat gun or butane lighter 435-04171 Peltier Cooler

Transcript of 6400-91 Peltier Kit - LI-COR Biosciences91 Peltier Cooler Installation Kit includes one Peltier...

  • 6400-91 Peltier Cooler Kit

    Continued on next page

    Installation Instructions for the LI-6400/LI-6400XTPortable Photosynthesis System

    IntroductionThere are two Peltier thermoelectric block coolers located oneither side of the LI-6400/XT sensor head, beneath the twofans and heat sinks. The block coolers regulate the tempera-ture of the air that is circulated through the leaf chamber. Thecoolers can fail in one of two ways; they can fail completely,whereby there is no change in the block temperature, or theycan become inefficient, and fail to modify the block tempera-ture over their specified range. In the case of total failure, oneor both of the coolers are physically broken, and exhibit anopen circuit condition. If the coolers function, but will notchange the temperature sufficiently, the resistance of thecooler(s) is likely too high, rendering it inefficient.

    This document describes how to test the Peltier coolers (thisrequires an ohmmeter), and replace, if necessary. The 6400-91 Peltier Cooler Installation Kit includes one Peltier cooler,and additional parts required for the repair, including:

    Qty. Description Part No.1 Peltier Cooler 435-041712 Black thermal conductor pads 108-033762 Shrink wrap 220-00291

    Troubleshooting1. See if the fans spin freelyThe LI-6400XT has circuitry that senses if the fans for thecoolers are running. If the fans do not turn, power will not beapplied to the coolers. Blow on the fan blades and see if theyturn. If they do not spin freely, they may be jammed; dislodgethe impediment, and the problem may be solved.

    2. Check the fusesThere are two fuses inside the LI-6400XT console, along theedge of the lowermost circuit board, labeled TEC- and TEC+(Figure 1). Check these two fuses before proceeding. Centerthe fuse(s) in the clip holder to make sure it has good contact;if the sides of the clip holder are flared outward, remove thefuse and pinch the clip until it makes tight contact with thefuse.

    PPS-274

    Figure 1. Check the fuses at TEC- and TEC+, highlighted above.

    3. Test the resistance of the cooler(s)a. Turn the LI-6400XT off and let it sit, untouched, for at

    least one hour so that both sides of the Peltier coolersare at the same temperature.

    b. Remove the three screws that secure the bottom coverof the sensor head IRGA (Figure 2). You may have topry the back end of the cover, and lift it enough to clearthe log button and light sensor connectors on the side.

    c. Follow the red and black wires from the coolers, andlocate the two 4-pin white connectors on the edge of

    Note, too, that in addition to these instructions, a videoshowing how to replace the coolers is available at:

    http://www.licor.com/6400cooler-replacement

    Tools required:Ohmmeter5/64” hex key (allen wrench)Wire cutter/stripperSoldering iron and solderPhilips head screwdriverTweezersHeat gun or butane lighter

    435-04171 Peltier Cooler

  • the circuit board (Figure 4). The red and blue wires arethe fan wires, and the other two are the cooler wires.Note that newer LI-6400XTs have red and black fanwires, so be sure to follow the correct wires back to theconnector if your fan wires are red and black.

    d. You will need to take a resistance reading for the twocooler wires at the white connector. Since an ohmme-ter sends a small current through the device under test,it will cause a good cooler’s resistance reading to changeas soon as you touch the leads to the pins on theconnectors. Make sure you have the ohmmeter in aposition to read the display, touch the leads to thecooler wires (polarity does not matter), and immedi-ately observe the reading (Figure 4). A cooler that is‘good’ will read under 5 ohms. If the reading is between5 and 15 ohms, the cooler will operate, but at a lowerefficiency. If the reading is over 20 ohms, open (infin-ity), or in the k ohms range, the cooler has failed andshould be replaced.

    Installing the Replacement Cooler(s)1. Don’t remove the four screws in the corners of the fan

    assembly; it’s much easier to remove the entire fan/heatsink assembly by inserting the 5/64” hex key downthrough the fan housing and loosening the two hex headscrews (Figure 5). Try not to let the screws fall completelyout of the fan assembly; it’ll be easier to re-install later ifthey’re still inserted into the holes in the fan assembly.This will remove the fan/heat sink assembly, and exposethe block cooler.

    2. Note that there is a thermal conductor pad on theunderside of the heat sink (Figure 6). Replacement padscan be found in the kit; the pads do not need to bereplaced unless they are damaged.

    3. Note that the red wire is located on the top of the cooleron the right side of the sensor head, and on the bottom ofthe cooler on the left side of the sensor head (Figure 6).This is important, as the coolers are in series with eachother, and work together; if one of the coolers in installedbackwards, the coolers will work against each other.

    4. Use a pair of tweezers or a small screwdriver to pryaround the edges of the cooler; it may be stuck to asecond thermal conductor pad underneath, and may needto be pried off. Loosen the cooler, but leave it in positionfor now.

    5. Use a pair of wire clippers and clip both of the coolerwires about 1/2” past the black heat shrink, just pastwhere the wires make a 90 degree bend, as shown inFigure 7.

    Figure 2. Remove the three screws that secure the bottom cover.

    Figure 3. Pry the bottom cover off, taking care not to damage thelog switch and light sensor connectors (highlighted).

    Figure 4. Follow the wires from the fan to the connector, and takea resistance reading at the connector. Polarity does not matter.

    Figure 5. Insert the hex key through the fan housing and removethe two hex screws that hold the fan/heat sink assembly.

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  • 6. Lay the new replacement cooler over top of the old one,and bend the wires on the new cooler to match those ofthe old cooler. Again, make sure the black and red wiresare oriented correctly. Clip the wires on the new cooler toa length slightly longer than those that were clipped onthe old cooler. Remove the old cooler and discard.

    7. Strip about 1/16” of the insulation off the two coolerwires. Unwrap the wires from the fan/heat sink assemblyfor a short distance, and strip the insulation from them aswell, about 1/16”. Tin all four exposed wire ends withyour soldering iron.

    8. Place the new cooler in position on the sensor head, ontop of the thermal conductor pad (replace the pad if itwas damaged while removing the old cooler). Beforesoldering the wires together, it may be useful to place apiece of masking tape over the cooler to hold it in placewhile you solder the wires (Figure 8).

    9. Place a piece of heat shrink over one of the black and redwires; they’ll be used later to seal the soldered joints.

    10. Use a pair of tweezers to hold one wire steady against theother as you solder the ends (Figure 9). Place the exposedends side by side to create a lap joint. Use a freshly tinnedsoldering iron and solder the ends together. Use thetweezers to slide the heat shrink over the newly solderedjoint (Figure 10). Repeat for the other wire joint. Use aheat gun or a butane lighter to seal the shrink wrap; passthe flame over the heat shrink until it contracts over thejoint.

    11. Note that there are two milled grooves on one side of theheat sink, as shown in Figure 11. These grooves face theback of the sensor head, at the 3 o’clock position. Thewires from the cooler must lay in these grooves wheninstalling the fan/heat sink assembly, so that the wiresdon’t get pinched.

    12. When the cooler wires are routed through the heat sinkgrooves, put the fan/heat sink assembly into position andstart, but don’t tighten, the two hex head screws. Alter-nate tightening between the two screws. Tighten onlyuntil you feel the screws stop; do not overtighten, as theceramic cooler underneath can be damaged.

    13. Reassemble the lower cover. Make sure the cooler andfan wires on both sides are not pinched between the coverand the IRGA block; use the tweezers, if necessary, toposition the wires in the two grooves on the front edge ofthe lower cover (Figure 12). Make sure that none of theother wires are pinched, and snap the lower cover intoplace. You can slide the lower cover back and forth at theleading edge, nearest the coolers, to see if the wires arepinched; you should feel metal on metal when the cover ispositioned properly (Figure 13).

    Figure 6. Note the thermal conductor pad on the bottom of theheat sink. Note, too, that the red wire is on the bottom of thecooler on the left side of the sensor head.

    Figure 7. Clip both wires about 1/2” below the heat shrink.

    Figure 8. Place a piece of tape over the cooler to hold it in placewhile soldering the wires, if necessary.

    Figure 9. Use a pair of tweezers to hold the ends together whileyou solder the exposed wire ends.

    Note position of redand black wires

    Thermalconductorpad

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    PPS-274, 7/14

    14. Replace the three screws on the lower cover. This finishesthe cooler installation. Turn the instrument on andchange the block temperature to verify that the cooler(s)is functioning properly.

    Figure 10. Slide the heat shrink over the soldered joints.

    Figure 11. Note the two grooves in one side of the heat sink;these grooves face toward the back of the sensor head, at the 3o’clock position.

    Figure 12. Make sure the wires aren’t pinched underneath theheat sink before tightening the screws on the fan/heat sinkassembly.

    Figure 13. Position the wires in the grooves at the front edge ofthe bottom cover. Snap the cover into place, rock the cover atthe leading edge to make sure the wires aren’t pinched, andreattach with the three screws.

    Grooves

    Groove

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