"A lot of these TI calculators are on auction on EBAY but it is surprisingly small knowledge on both sellers and byers side to recognize. First thing for all sellers to know: NEVER USE A TI 58,58c or 59 WITHOUT THE BATTERY PACK! The AC adaptor will supply AC current to the calculator and the internal circutry relies on the battery pack to generate the right voltage levels for the internal circuitry. For Sellers and Byuers: Every TI 58,58c,59 has a build in check routine to run a quite good check about the working conditions of the calculator press 2nd Pgm 01 and then SBR = After a couple of seconds a number should appear . If this number is flashing your TI is in some trouble. This does not mean that you can not calculate, TI58c will be an excellent calculators even if the cmos memory is fried! To know which steady number should appear , open the small bay at the bottom of the rear side (slides down ) the number on the module is the numer you will see if the checks runs OK.Most imes it will be the Master library module with the number 1. If there is no module, you can not run the check. TI59 Magnet card reader Run a magnet card by simply inserting it in the lower right hand slot (look carefully, there is one!) You will feel a little resistance until the card is in for ~1/3 if nothing happens then stop, do not force anymore. The card reader is not working. If the reader motor starts (shocking loud if you have never heard it before ) and the card is not sucked in, do not force it, turn the TI off. The rubber weel is done. This can be repaired but is tricky. If the card runs through and a steady number between 1-4 is shown....Great the reader works. If the number is blinking, try again. If it does not work then either the card had no program on it(try to find one with a program) or the reader is misaligned. This is no big deal as inside the battery bay you will see a adjustable resistor which controlls the reader speed. How to adjust the reader? Please download the TI 58/59 mantainance manual for details."