Seems that most modelers have heard rumors about the JR Lithium battery and the need to replace it. Most "Know" that you have to send the transmitter back to JR to get this done. Some have had transmitters for years and report that there is no need to replace it. SO, what's the real story? Well, there is a lithium battery in the traditional JR radios. I had purchased a 347 some 7 years ago and recently, it lost the model settings and had an error indication on the front panel display. Seems that lithium batteries have a shelf life of 7 years and last just as long in the JR transmitter. We decided to have a go at replacing the battery ourselves. Note that this repair will void your warrantee and FCC might not like the fact the we modelers are doing work on our equipment. However, I was a licensed HAM radio operator for years (WB2SXC) and allowed my license to expire. I have built, modified and operated lots of transmitters, most at 100 watts and more. The battery replacement only requires simple soldering and does not effect the transmitter in any way... Well, with that said (this was the small print they talk about) lets see the details... Removing the six screws from the transmitter back will allow you to access the interior of the transmitter. You will need to carefully pull the front and back assemblies away from each other. Notice the wires that join the front and back. These can be unplugged by gently rocking the connector from side to side while pulling on the connector. Do not just tug on the wires or you may end up having to repair the wiring. For making adjustments of the stick tensions, you need to disassemble your transmitter to this point anyway, so no problem with the warrantee (yet). This shows the front and back separated. We are interested in the circuit board mounted on the lower front case of the transmitter. Before getting carried away with this repair, we can test the battery from here without removing anything else. The points indicated by the arrows are the locations where the lithium battery is soldered. The positive solder trace is labeled L1 on the 347 transmitter. The point toward the bottom of the transmitter circuit board is the negative terminal. The voltage measured across these points should read 3.0 volts DC. Mine read 0.517 on one transmitter and 2.519 on the other. The one reading a half volt was the trouble one (the other one probably has many months left). Now that we have determined that the lithium battery needs to be replaced, we will need to get access to the bottom of the circuit board. There is only one screw holding the circuit board on the front case. The four nylon ties that are used to keep the wiring neat were cut and removed. Be careful as you pry the circuit board up in the next step, the six push buttons have six springs on them and may come loose. Keep track of these, you will need them. Gently prying the circuit board up will allow you to gain access to the component side of the circuit board. Now we will heat up our soldering pencil and remove the old battery. We used a solder sucker to assist in the unsoldering operation. You will need to gently pry the battery from the circuit board as you heat the solder. As shown above, you will need to unsolder the battery from these two locations. Once the battery has been removed, you can replace the circuit board. We will solder the new battery on top of the circuit board, since there is plenty of room. The hardest part of the repair is getting the push buttons and springs lined up with the switches as you press the circuit board back into its location. It took us two tries to get this one back together. Test all six switches to make sure they work properly before proceeding. This can be the most difficult part of the battery replacement. Once they are OK, reinstall the screw to hold the circuit board. We went to Radio Shack and purchased a CR2032 Lithium battery for $2.99. The package said "Best if used by Apr 2009", so we should be OK until 2009. (Check back and I'll update this web page.) SO, we used a high heat soldering pencil, some flux and solder to solder wires to the new Lithium battery (this voids the Radio Shack warrantee, I'm sure). Using a high power soldering iron and applying the heat in as short a time as possible to tin the battery and solder the wires is the best method. This is less likely to damage the battery. A small soldering pencil may actually do more damage, since you have to apply the heat longer. Once the two wires are soldered to the battery, test the battery to make sure it still reads 3 volts DC or more. Whew! We added some heat shrink tubing over the battery and solder connections. Next we soldered the battery to the circuit board, being careful to only solder the red positive wire to the location marked L1 and the black negative wire to the solder pad nearer to the bottom of the circuit board (the points the the original battery was desoldered). Once the solder has cooled, check the voltage between the two solder locations. It should read around 3 volts. Congratulationss! You have successfully replaced your battery! We added some double tape Velcro to the battery and pressed it into place. We also used nylon cable ties to dress the wiring back neatly over the circuit board in their original locations. Well, the replacement is completed. We tested the transmitter before replacing all of the screws. Don't operate the transmitter for very long with the case separated. Anyway, our transmitter worked just fine... NO errors and the transmitter kept our modulation and plane names just like it did for years. Now, if the notes can be located for the four planes' original settings that got lost, we'll be all set again. Repair time: 18 minutes. Cost $3.00 plus tax. Not bad.  Builder's Corner  Barnyard Buzzards Home Page