Repair HP16C

[Manel]

Hi,

I bought one non working HP16C, some time ago I fixed one HP15C and the only problem was that a track was corroded.
The 16C had a lot of corrosion, but after clean and repair the tracks, it does not turn on...
After shortcut the battery contacts now it shows this screen when I put the batteries:

- |-,|-,|-,|-,|-,|-,|-,|-,|-,|-
USER f g BEGIN GRAD D.MY C PRGM

(see attached picture)
The keyboard does nothing...

What can I do ?

Thanks in advance

Manel