Hi, Thanks for quick reply ! I have tried the changes you suggest but still no signs of life. I should perhaps have mentioned that I am using a Pickit 2 to proram the 16f628a and have it directly connected to pins 12,13,14 and 4. Having prorammed it ( and there is a hex file in there if I read it) I remove the Pic Kit and connect and external supply as the coil would draw more current than the pic Kit would be happy with. Can't help thinking I am doing something seriously dumb here (not for the first time !