Changeing the battery
With special thanks to Mikal Phillips for this article
First unplug your Juno and open it back up. Also touch the metal part of the case BEFORE you touch the board (in case you have any static built up on your body it will dissipate into the case and not the circuit board).
Look at the battery and how the terminals go into the circuit board. It is
on the top side of the circuit board and about the size of a quarter. The
battery should be, "standing" facing up and down (I.e. not laying flat on
the board with only one side showing).(At least that's how it was originally
on my Juno that I had bought second hand, so if it IS laying flat, GENTLY
bend it upwards to stand it up so you can access the leads.)
If it is an "original"/ "stock" battery the silver leads are permanently connected to the battery itself and cannot be removed. So you will need to remove the entire battery/lead assembly from the board by carefully desoldering the two leads that terminate into the board.
REMEMBER WHICH WAY THE BATTERY IS FACING ON THE BOARD (I.e. note which way the "+" side is facing) BEFORE YOU REMOVE IT FROM THE BOARD. I think the way the battery is hooked to the board polarity -wise may make a difference.
What you need to do is GENTLY de-solder the leads that come off of the battery and go into the board. (I recommend getting a de-soldering tool to use to suck out the excess solder when you heat it up). (I also recommend using smaller soldering irons for close-in work and STAY AWAY FROM LARGE "GUN-STYLE" SOLDERING TOOLS. The electonic field the heating coils genertate in those larger guns can harm sensitive microchips on a circuit board).
Carefully put the tip of the soldering iron on the lead where it goes into the board, siphion off the excess solder and while it is hot gently pull the lead out of the board. Repeat for the second lead on the other side of the battery. DONT'LET EXCESS SOLDER, "STRAY" INTO OTHER LEADS ON THE BOARD, THIS COULD CAUSE A SHORT.
Take the old battery to your local electronics store (that sells watch/specialty batteries) and ask them if they carry this type of battery. Odds are they will have it in stock or can order it for you.
NOW, I have done 2 battery replacements on my Juno 106 (the average memory battery life is about 2 years). The first replacement battery HAD the 2 silver connectors already attatched to it, so all I had to do was solder the battery assembly back into place on the board. (You may need to crimp/trim/fold the very ends of the leads so they will fit properly into the small holes on the board). The second time around the new battery did NOT have the leads on it, so I had to make my own "jumper" connections for it. (Which is pretty easy, here's how...)
Get some SOLID core, small guage wire. (about 22 guage, i think will do) Cut two 1/2 inch strips. (About 1/2 inch should do but you can cut longer and trim down if necessary once the ends are attatched to the two sides of the battery). Strip each end of the two wires. On the ends of the wire that are going to be attached to each side of the battery, melt a little extra solder on those ends so it will be easier to solder them to the battery (this is called, "tinning" the leads). Put one lead leading off of the "+" side and one off of the "-" side (I soldered the leads onto the middle of each side of the battery so I don't have to worry about any possibility of a short). Bend the leads so that the battery can "stand up" and then bend the tips of the leads that are going into the baord down so the can go back into their respective holes on the board. (So the 2 wires are like an,"L" coming off each side of the battery). Carefully heat up the hole on the board and gently push the new lead down into the hole. Put a little bit of solder over it to secure it to the board. Repeat for the other side. Check to make sure that any bare parts of the leads going into the board do not touch any of the other connections around it (It is ok if the leads rest on any green unused areas of where the new battery is sitting).
Reassemble your Juno, plug it in, turn it on (wait breathlessly for a few seconds to make sure it does not explode...just kidding). If it does not power up you may have caused a short somehow but chances of that happening are very low.
Create a patch and save it (or load the original factory patches if you have them). Play your new patch for a bit... then turn off your Juno. Count to 10, turn it back on and call up your patch. If it sounds the same as when you made it then YOU HAVE SUCCESSFULY REPLACED THE MEMORY BATTERY ON YOUR JUNO! CONGRAGULATIONS!
If it DIDN'T save your patch to memory then the battery is not connected properly, open the case back up and check the two battery connections again carefully.
ALSO, ALWAYS REMEMBER TO BACK UP ALL OF YOUR PATCHES ON A REGULAR BASIS (Save them to tape, so if your battery does die again, you won't permanently lose all your patches)
Aaron Simpson gave me the following hint: Useing a battery holder - e.g. from an old 486 PC board - you may change the battery in future without soldering.