WTB - Raymarine #650 Autopilot Head

[Ray 40]

My #650 has decided not to work in the 'Auto' mode. 'Standby' works fine and I still get Rudder position indication. In 'Auto' mode I get blinking 'Low Battery' signal.
There is power available and Raymarine tech says "head is dead" - seems odd as I've switched Bridge and Salon heads and both give 'low battery' signal (dual death???)

Anyone have head/heads for sale? Will #6000 or #8000 series heads work with existing brain/set-up??

Thanks