I have a Geller SX-690 cash register which has started to error.

It allows the user to sign in but displays "Memory Over" when I try to key in a product. It will let me perform a "No Sale" to open the drawer. The Till was working fine last night but has developed this problem this morning on the first operation, has anyone got any idea how to solve the problem - If you have I will be eternally grateful!

Colin Stroud