Could be a simple problem like a fuse blown. Look for the general illumination or GI fuse

+1
also check the connectors on the interconnector board to see if they are burnt out
the interconnector board is the long skinny board at the bottom center in the back box

check fuses F1 to F4
check connectors J6 and J9
if the lights behind the translight (back glass) are lit ok then bridge rectifier should be ok.

if the G.I behind the translight are also out the check the connections on the bridge rectifier and fuse in the right bottom corner of the back box next to the interconnector board (the fuse sits on the side panel of wood in the back box)
also check the fuse in the right bottom corner of the back box (only if all the G.I. are out including the ones behind the translight)
if this fuse is blow and you replace it and it blows again then it is safe to say that the bridge rectifier has failed