Lower the freq it mines at and see if it comes back. These are old machines now so more than likely that chip wont come back but its worth lowering the mining freq just to try it out.
chip is on "o" every time i reboot the machine, let me try lower the freq to see if that work, thanks for fast reply.
It will show the "o" to start with usually but then after a little while it will drop out to an "x". Lowering the freq will draw less voltage so it might last longer before dropping out or stay good permenantly. One chip wont affect the overall hashrate though so don't panic