Repairing HP-41CY TURBO from W&W

[cellfun]

Hello all,

Finally, I got the HP-41CY TURBO ... Unfortunately, it doesn't work...

After putting new batteries I see a "MEMORY LOST"-message only. Nothing happens while pressing the buttons.
Any ideas what can be the cause?

Some additional questions:
- what kind of batterie is used for the W&W-Board - a 3V or 5V?
- I found another micro-switch on the W&W-Board - but what for?

Any help or a hint is highly appreciated.

Kind regards,
cellfun