Sonos 5500 error DFD28-0001

I have a 5500 that won't boot up period. The upper screen is on but has no image period. The lower screens don't display anything.

The Back processor displays DFD28-0001

~~~~~~~~~~~~~~~~~~ From the manual ~~~~~~~~~~~~~~~~~~~~

xFD28-xxxx Indicates that the processor ROM failed core test. Four digits
of additional information indicates the ROM that failed.

Where the leading “x” can be either a K (Keyprocessor), D (Scan Converter), or
E (Scanner), representing the keyprocessor that has failed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The 3.6 V battery was completely dead, so we replaced it but it didn't help the problem.

Has there been a Rom failure? Or did it lose the BIOS (or some other memory) setup?

We're not sure where to proceed from here. ???



Any help would be appreciated.



Thanks

P M Ilyas