27S MEMORY LOST - what's the cause?

[rprosperi]

It might be improper contact of the battery terminals. Though this is not a common problem in Pioneer machines, it does tend to happen in those that have had some kind of battery leakage in the past.

The simplest and best (and as a bonus, cheap) to clean contacts, for any calculator or other kind of device, is with a glass brush. Here is one from Amazon:

https://www.amazon.com/gp/product/B0019V18D2