This page may help technicians and repairers solve common problems with some laboratory centrifuges. (Warning: untrained personnel should not attempt to repair this equipment due to the risk of electric shock from high voltages inside. Also, be cautious of biological and chemical contamination: the rotors and the inside of the centrifuges may be contaminated with bacteria, viruses, human fluids, DNA, RNA, and toxic substances.)
The Beckman Allegra 21R centrifuge was not reaching an adequate speed: the rotor started spinning, but did not exceed 100-200 RPM. No errors were displayed, making it difficult to diagnose the problem. This type of defect is related to a motor speed sensor that does not send correct data to the circuit board, preventing the rotor speed from being controlled.
The cause of this malfunction is the magnetic cylinder (similar to a ball bearing) at the bottom of the motor shaft, which communicates the motor speed to the control board via a magnetic field sensor. This magnet can detach from the motor shaft or remain attached but rotate freely, preventing the sensor from properly detecting the speed. Here are the steps to fix the problem:
In another Beckman Allegra 21R centrifuge, error 28 appeared on startup, and sometimes the "notA1" error also appeared on the display. Despite attempts to reset using the control panel (pressing the following key combinations: press the up arrow once, press Enter twice, press Enter a third time and hold until the menu appears on the display, scroll through the menu with the arrows to select the reset option), the error kept reappearing. However, the problem turned out to be the same as the magnet issue we just described.
The Eppendorf 5415D centrifuge was displaying error 17. After consulting online resources such as https://staff.washington.edu/wbeaty/chem-eppndrf.html and https://www.labwrench.com/thread/219547/resolving-error-17, it was determined that the problem was with the electrolytic capacitor near the UC2844 IC. In some cases, the capacitance of the capacitor may decrease under voltage, even though the capacitance meter does not detect any apparent defect.
Here are the steps to follow to resolve error 17:
Later, I noticed that the encoder knobs were slightly stiff, and sometimes the time and speed values on the display would change by two steps at a time with each click of the encoder. Sometimes the clicks of the encoder would not cause any change in the digits on the display. I replaced the encoders and the problem was solved. When I took the broken encoders apart to see what the internal problem was, I found that the rubber parts inside the encoders had degraded, like rotted and fragmented. A word of warning: do not use any spray or deoxidizer for encoders because the solvent that gets inside can swell or deform the rubber parts.