RC 30/51 no messages on start up

Hello,
we have IR 761 with RC 30/51. After switching power ON there is no any message on the display.
Any help highly appreciated.

Thanks.

Hello Panic Mode,
thanks for attention.
there is no image - blank screen. May be for a less then a second something appears, but so fast i can not see it.

thanks.

Hello Panic Mode,
i took out motherboard and communication board.
there was some dust, i cleaned them and now control works again.
unfortunately all machine data were lost.
now will try to enter them again.

thanks for helping.