As I mentioned in an earlier thread, I am trying to repair a DEC Professional 350 system board. I think I know the pinout of the F11 chips is the RESET signal? If that is correct then it is oscillating and resetting the machine constantly. I am trying to trace the source, but it seems to go through quite a few chips and I haven't yet traced its source. The chips where I believe the RESET is oscillating on pin 23 have been labelled E151 and E152 in the following photo: https://rjarratt.files.wordpress.com/2018/10/system-board-labelled.jpg But I am not really sure if I have identified them and the pin correctly. Thanks Rob