Power but not spining

First, before I tell you about the brushes, I need to inform you that you using a piece of instrumentation that is to say the very least, DANGEROUS to continue to use.  That model of centrifuge was discontinued over 20 years ago because of safety concerns.  The latch on the centrifuge is the biggest short coming as it has no secondary latch to prevent the chamber door from opening in the event of a rotor mishap, which depending on how old the rotor that you are using is and HOW you are using it is the other maor concern.  In the event of a rotor mishap, the chamber doors have been known to blow open and fragments of the rotor have escaped the chamber because of this failure.  That is why I do not recommend you continue to use that centrifuge.

However, if you are still inclined to replace the brushes, unplug the centrifuge and then after removing the rotor assembly you will see that there is a rubber boot around the bottom of the chamber that must be removed by peeling it up.  Once the boot is removed, you will see see 6 locking nuts that must be removed and then the 6 rubber gromments must also be removed.  It is recommended that you get a brush replacement kit because those grommets frequently get squashed down over time and no longer provide the same performance and the kit includes new nuts and grommets.  At this point, you can try to lift up the drive from its mounting screws but you probably find that it appears to be stuck in place.  This is because the material tends to get very sticky over time so you have to pry the blue shock mount material and the drive assembly free.  It takes time and patience to do this and you will have to work your way around the entire circumference of the drive assembly to get it free.  Eventually, you can raise the drive up just enough on the right hand side to get to the brush there.  You won't be able to remove the drive completely because the drive power and disc brake cables are still attached.  To get to the other brush, try to pull the drive up and over to expose the other brush.  You MUST follow the instructions that come with the brush kit as to the correct way to install the brushes because there is a correct way to install them.  If you can't get the drive motor free enough to get to the brushes, then you will have to open up the front cover of the centrifuge and disconnect the two cables that are attached to the drive.  This will allow you to remove the drive enough to get to the brushes.  After you have successfully replaced the brushes, you need to break them in by running the centrifuge at 2000 RPM for around 2 hours.  After that, you can continue to use the centrifuge but again, I strongly caution you that you are dealing with an extremely dangerous centrifuge.  Before I retired from Beckman Coulter, we were absolutely forbidden from even working on a GP/R centrifuge because of the safety issues relative to them.  Proceed at your own risk and caution but you have been warned as t o the inherent dangers with this centrifuge.

Thanks for your help. I did not know about the safety issues of the model, tho I knew it was old. I will try to convince my administrators to replace this instrument as soon as posible to avert an accident. Again, Thank you