Discussion Category: Centrifuge
Beckman Coulter J6-MC Deceleration not functioning
We have Beckman Coulter J6-MC. About four months ago, the speed indicator stopped showing the speed of the rotor in RPM´s. Instead the "frequency" of the revolutions of the rotor appears in the display. (We discovered this after measuring the the real speed of the rotor with an external calibrated instrument. We found out that the value of "1100" displayed in the RPM indicator of the corresponds to 4000 RPM).
Last week we fould that once the timed cycle was completed, the rotor coasted to a stop instead of using the "maximum brake" we had programmed.
We tried programing the three options available for the braking system but it appears that none of the options (except "coast to 0 rpm") works.
The acceleration is ok, and the speed is maintained for the programed time...it's the braking circuit that doesn't appear to be functioning correcly..
We have checked fuses (the ones we could find). We have looked at the resistor at the back of the centrifuge but we are not sure what we should be looking for.
Can anyone help us?
Thank you in advance.
Reply byFirst, it sounds as if you have the centrifuge set up to dispaly the omega square t (angular acceleration) in the speed display field. You should be able to toggle that back to speed from the control panel. I, personally, have never encountered a no brake mode unless the customer has set it up that way on your model of centrifuge because usually if there is a problem with the drive circuitry it will impact both the acceleration and deceleration rates and you stated that it getsup to speed quite fine. Also, "coast to zero" would be the same as none of the other brake modes working properly because you would be coasting to zero if none of the other modes are working. Get out your DVM and check the resistance across the brake resistor with one of the resistor leads disconnected from the centrifuge wiring and tell me what your reading is. Again, in over 32 years of working for Beckman, I NEVER saw a single brake resistor fail so I will be very surprised if your's has now. What kind of rotor are you spinning? I will have to think about this one a little bit more because of never having seen this problem before..
Reply byFirstly, thank you for your prompt reply.
With respect to the angular acceleration appearing in the speed display field - we cannot find a way to toggle back to RPM. This, however, is a relatively minor inconvenience as we have a table to convert the angular acceleration values into RPM so we have no problems programing the real speed of the rotor.
I will try to read the resistence across the brake resistor with one of the leads desconnected from the centrifuge as you have described.
I don't have circuit diagrams for the centrifuge so I don't know if the brake circuit has some type of solid state relay or other component which would cause the inactivation of the brake circuit without affecting the acceleration.
Our rotor is a JS-4.2A
The centrifuge is not used intensely (in a week, we would do about 15 cycles, 4000 rpm, 20 minutes) and we carry out the usually maintenence operations regularly.
Reply byI have checked the resistance across the brake resistor with one of the resistor leads disconnected from the centrifuge wiring.
3.5 - 4.0 ohm
Reply byObviously your brake resistor is OK so that's not the problem. It looks like you're down to an electronic malfunction of some kind since this behavior is new to your operations. Correct?
Don
Reply byI agree, the most logical conclusion is an electronic component has failed. In the last week we have run over 20 cycles, all showed normal acceleration and speed during timed cycle but "coasted to zero" at the end.
The only options left are replacing the circuit board which controls the brake (if they can be found) or replacing the the entire centrifuge.
Thank you again for your time and help with this problem.
Reply byThe other issue with your centrifuge is that it is one of a series of centrifuges that Beckman Coulter put under obsolescence many years ago. This means that service became pretty much non-existent as was parts availability. Sorry to not be able to offer you any other options but I have not seen one of these centrifuges in a long time and I don't have access to my paper manuals where I'm living at right now. If I can actually get access to my manuals the next time I'm back at my old stomping grounds, I will get back to you if I can come with any other options if you still want to try to make repairs.
Don
Reply byi need service manual of beckman j6b
my email shanahmad010191@gmail.com
Reply byAs to the brake problem, K103 is the relay that energizes in order to switch the drive system in to the brake mode by running the drive power through the brake resistor along with reversing the field in the motor so that is where to look first for that problem. K101 nad K102 also have to function properly as well as other components on the DRIVE CONTROL BOARD ASSEMBLY. Understand that there is a control signal that causes that relay to energize so a bad control board could cause this issue. The collector of Q602 on the backplane board should go low in order to energize the Brake relay function via other components on the DRIVE control board.
As to the speed readout, there is no known way to switch the speed display from reading anything other than the speed and I was erroneous in my first post on this issue. As you discovered, the number you see with your measurement equipement has nothing to do with the speed readout. The fact that the measured speed equals your set speed says that the speed control is working fine but the display function is not. Also, is the keylock in the RUN position as opposed to the LOCKED position? The pulses from the TACH sensor are counted on the backplane board which is the board with the displays on it. A problem there could be the source of your erroneous readout.
Don