APF MARK 31
The APF MARK 31 is an arithmetic calculator with 8 digits precision and algebraic logic. It has 9 functions, 27 keys, and a VFD (vacuum fluorescent) display. The power source is PP3 9V.
Facts at a glance:
|Power Source||PP3 9V|
If you have an APF MARK 31 that is no longer working, you can first try replacing the PP3 9V battery. If that doesn't solve the problem, then you can consider replacing the calculator with a modern equivalent. We suggest the following current models as possible replacements: