CVS-1458 cannot boot

[heel]

We have two CVS-1458 (P/N 158022A-DSL). They have been running an application 24/7 for at least 10 years without any issues. Recently there was a power-cut and both no longer boot up.

The 3.3V supply is fine. Nothing appear burnt. The backup battery was down to 2.7V and has been replaced.

Attempt to boot into bios holding the Delete key (as the bios update manual says) shows no activity on the VGA port nor the USB bus. The indicators are as shown in the figure below. Drive starts yellow for 30sec then blinks at 2Hz.

We suspect that it is the bios which has been corrupted from the many years in operation and only now, when the device has to reboot, the problem appears simultaneously on both modules.

Question: Any idea of what to try before we sign them off duty? 

Thanks