The projector is projecting to the screen and shows in colour the logo etc but when i try to connect to dvd or piped signal it just continues ' seraching'. Previously worked perfectly Infocus Realplay 5700 projector

The input is normally selected automatically as the logic switch tries to gates with the input sources scanning to find the signal present to latch ON.
Now if the scanning -searching-does not give a result it is due to the fact that the main processor is doing the job well to instruct the sub logic IC to gate which is not switching on to track the signal that is present at the input source.
The Projector is working well on the output side but the fault seems to be in the source selection. You can disconnect and check to see if the connecting cord of the DVD is working by trying it on the TV. Confirming the DVD signal cord , the fault must be looked in the Main board. The RCA input to the preamp, the switching IC logic must be checked for the possible fault.
You will need a good knowledge of logic gates to check , confirm and replace the faulty component or IC. If you are able trace the track from the RCA input with a signal to see where the signal is cut off. A loop over in this section with a coupling capacitor will give the picture while confirming the faulty device.