Odd fault in Roberts R827!

[Old Sparky]

Not sure if this should be here, or in the 'Vintage valve & Transistor Radio' section.  Anyway the fault is that the radio is 'on' all the time, in what seems to be VHF/FM but the display is blank, and none of the controls, except the tone & volume ones, have any effect.  It doesn't matter whether the set is powered from batteries, or from it's external 'wall wart' mains PSU, with or without the batteries inserted, the problem is the same.  I don't have a circuit diagram or service manual for this  Sangean multi-band 'clone', and Roberts no longer supply any info. or spares for it.  I have yet toremove the covers for any internal checks, and haven't checked the memory back-up batteries, but don't see why failure of these could prevent the display & controls from working.
Does anyone have any idea as to the cause of these faults, please?

[Refugee]

It might have got wet at some time. This would leave deposits on the keys and display but it can often be cleaned up if the tracks have not rotted through before the deposits dried on.

[Old Sparky]

I have, at last, got around to dismantling and checking this radio. Everything seems to be working perfectly in as much as the radio can be powered both from internal batteries (4 x 'C' cells) or it's outboard 'wall-wart' PSU, and all wavebands & functions are working. It seems that the problem mentioned in my first post (display blank, but audio amp. on) is to do with the 'standby' circuit fitted to the R827 and isn't really a fault at all. If it's still available, I'll download the User Instruction manual, which should explain things!