Thanks for your replies.
That was going to be my next step. It would be good, but unlikely, to find a schematic for this unit, or even some programming info from Agilent.
I was told that Agilent said they could repair it, but would charge around $4000. So it is repairable but like most things, depends on getting the right info and of course even if I was able to flash the MCU and or other parts getting the firmware etc may be a big challenge, if not impossible. I am sure Agilent could help but I was told they were really unhelpful and only offered a repair at this price and also said that it was not a guaranteed fix, so $4K could be spent on just getting back another brick!
I will spend more time looking into this further before ripping it apart for spares.
Thanks
John