s type (1999) radio no sound

hi, had an intermittent sound problem , then I noticed if I placed gear selector in park sound on, in drive sound off ??,  wasnt like this earlier when sound lost,

I thought maybe an earth fault, also recent water ingress to interior around gear selector area... now resolved as blocked drain in sunroof tray cleared out..

I removed radio binnacle and sprayed wd40 type fluid into connectors / removed excess fluid , pins all ok clean, 

refitted radio now total loss of sound..

I think must be a dry joint inside radio, also plugs very tight in sockets being as careful as possible so as not to strain board inside etc but its 20 yrs old so 

maybe made problem worse ?

says premium on rear of radio, but not on front like some ive seen, I dont have a workshop manual for wiring and cant find info on internet which explains this fault..

any help would be great 

thanks