Possible Solution for ERR & on 5424/5424R...

I had a persistent error 7 (or sometimes error 6) on a researcher's Eppendorf 5424R centrifuge. There are two possible culprits: the main control board/sequencer or the motor (actually the sensors built into the motor). It's pretty much a coin toss. A $1,200 replacement main control board/sequencer got it to a more consistent error 7. We could increase the rotor speed in small increments like 500 RPM without much problem, but if you tried a big number like 5000 RPM it would error out. Rather than gambling another $700 on a motor, I removed the Hall encoder that is built into the bottom of the motor. (Removing the motor is much easier than replacing the main board/sequencer card, BTW.) I retouched a few of the solder connections, removed some small magnetic chips and detritus clinging to the magnet, and tightened the card back in a little more snugly to reduce the Hall effect gap as much as possible. I am not certain which one of those things were causing the problem, but no more error 7. Good luck!