I am getting this alarm on several machines. I have checked the brushes, they are OK. Does anyone know of a way to troubleshoot them instead of just ordering board after board.
Thanks in advance.

Have you checked to see if the bp is actually stopping. I have seen in the past where the alarm appears than the bp stops (in reaction to the alarm). If that is the case there are two things to check the magnetic on the back of the rollers and the reed sensors that detects when the rollers are going past it. Good luck.

Ive had the same problem in the past with blood pumps on and off on some of the units. I usually check for alarms that would cause it to go off. But other than that I still replace the brushes, it solved my problems. Or try the famous Fresenius swapping technique.