I believe mine has the A Revision because of the way the keypad looks and the serial number also starts with a 3. I've tried everything I could think of, but someone here might have a better suggestion. The calculator let me boot to the download mode (V16 for mine), and even let me flash both old and new firmwares. I have tried literally all the firmwares I could find on https://www.educalc.net/2336439.page, and latest one as well. I did the flashing without the battery installed (Samsung S3 battery), and with the battery installed. Every time the flash is a success. It goes through 3 blue bars, but it just will not boot pass x^2+y^2 = 1 screen after the flash is complete. Depending on the firmware version, it sometimes sits on x^2+y^2 = 1 screen, and sometimes just keep restarting in loop. I did format the disk every time before flashing a new firmware by going to the CFO menu, but nothing seems to work. I came to the conclusion that something must be wrong with the hardware, as that is the only explanation that would make sense to me at this point. I really wish parts for this calculator, such as the motherboard were available to buy. Any suggestion is certainly welcome, and thank you for taking the time to read this post!