The HP-15C Limited Edition have a problem with the blue function "g" key was not responsive at first pressing it. The other keys worked well, but not the "g" blue function key. I have e mail HP, but no replies and their supply of HP-15C Limited Edition is still wild by speculators. I am stuck with a defective "g" key that HP has not interest to repair. I taken it apart to try to try to access the contacts on the top side, but unable to. The circuit board is melted plastic tight. I can tear it down to be able to view the Atmel ARM RISC microprocessor. There are three small, tiny springs to ground the top and bottom metal covers of the case that matches with the circle holes in the bottom plastic chassis with metal plate. The two CR2032 Li batteries are wired parallel. The circuit board has two separate 3 V DC input as seen in the picture with separate two blacks (-) wires and two reds (+) wires in parallel. I am not please with the new HP after merging with Compaq, ARM, Digital, Tandem, and Kinpo. I liked the old HP more. Everything works on the HP-15C Limited Edition, except the "g" key, that needs a little wiggle or press in a tad more than the rest of the keys.
To open the HP-15C limited edition:
1. remove the battery cover
2. remove the 2 CR2032 batteries.
3. discharge yourself.
4. gently ply the four rubber feet and use a small Philips screwdriver and remove the larger lag screws.
5. remove the larger lag screw in the other inside of the battery compartment.
6. remove the small lag screw by the reset button by the battery holder inside the battery compartment.
7. There are six lag screws total, remember this. The single smallest lag screw is the one on the lower right side of the battery compartment with a recessed underneath the lower right side battery holder corner. Mixing the screws will break the case. The larger lag screws are around the sides of the calculator.
8. Use only fingers to ply the case free, be careful of the four battery wires battery. They are delicately point soldered onto the main circuit board on the top side of the case and the battery is on the bottom side of the case.
9. Be careful of the three spring grounding conductors on the two plastic sleeves at the corner of the case next to the lag screw holes and the plastic sleeve by the reset switch. There are three springs two shorter length and one longer length. Be careful to not pop, drop, or lose these springs. The shorter length ones go to the corners and the longer length one goes to the top middle by the back of the display. You will noticed the circular slots where these springs will make contact with the metal plate in the bottom of the case for grounding.
I cannot take it apart further than this to repair the less responsive "g" blue function key. I did reassembled it back to original and just use the calculator as is. HP keeps running out of the HP-15C Limited Edition, so replacement is not possible and HP has not replied back. There might be some contaminants on the contacts from the Kinpo manufacturer or defect in the contacts or it might be a capacitance keyboard like my Fluke 12 digital multimeter sometimes need disassembly to clean the key pad to work. I have no way to tear it down further to try to repair the "g" blue key. It works, but I have to press it more or wiggle it slightly. I do not know. I wished Kinpo would work on this problem. I have this exact same problem on my HP-49G+ with the Symbols key that allows me to chose a function or graph software. The Symbols key has to be wiggle to right side to get it to work. I like the TI CX CAS in color more, perfected machine.
Battery consumption is very good to excellent. I have not owned it for two years to be able to let you know how long it lasts in actual usage. It is less than a month old, about two weeks old. It can run on just one CR2032 battery with the second battery removed as it is a parallel circuit. The memory is retained even with just one CR2032 battery. Replacing the battery while retaining the memory is done by replacing one battery at a time, while leaving the second battery in place. Once the first battery is replaced with a new one, then the second old battery is removed and replaced with a new one.