Fruit Machine Chat

I have a just bought a barcrest hyper viper machine which wasnt working, i have managed to get the machine to power up but i have an alarm "alarm 17-38 pnd opto blocked tamper" i have checked the door switches,fuses,connections and everything seems fine.
Has anyone got any ideas what i could check?

Thanks
Dave

its the ir light sensor under the hopper which counts the coins out, its either dirty or blown, one of the techys on here will advise you how to get to it, all i know is its under the rotating drum in the hopper. or there abouts.