Beckman J-6M taking too long to reach speed set point

What rotor are you using in your centrifuge?  Even the heaviest rotors should not take that long to get up to speed so you are probably looking at an electronics problem.  If you drop the lower front panel, you will see a slide out chassis that may be held in place by two screws.  On that chassis are 3 switch boards that should have alternating LED's showing the boards drive transistor circuit switching off and on.  If one of the sections on one or more of the boards is NOT switching off and on then that will be the problem.  The board can be repaired or replaced if you can find the components and you will usually find that the corresponding fuse has blown for that section of the board.  Start there and get back to me.

Don

Hi Don, thanks to the prompt reply. I'm spinning a JS-4.2 rotor but it now takes 10 minutes to reach 4k and the 3 pcb led's stay solid. Is the time to get to set point normal?

Thanks

What are the LED's doing when the centrifuge is not running?  Once you tell it to start a run they will be switching off and on so fast that you will not be able to see the changes.  10 minutes does seem a little long even for a JS4.2 rotor but how much of a load do you have in the rotor?  How fast did it get up to speed before you noticed this problem?  Have there been any other changes with the centrifuge like has it been moved?

Don

This unit was only getting up to 400 rpm and after leveling and greasing rotor pins were at the present state. With the speed at 4k, a JS-4.2 rotor and accel at 9 the spin is as follows,

500 rpm in 30sec and led's go from flashing to steady- up to 700 @ 1:15 mins and drops to 550 before returning to 700 @ 3.15 mins- drops down to 600 rpm (1 led solid and 2 off)- up to 760 @4.10 min and the led's seem to stay solid till reaching 4000- it takes 10mins to reach 1200 then 2500 @ 12 mins and surges to 4000 rpm @ 12.4 mins

The led's are flashing when the unit is not spinning.

I must say that it has been a long time since I even saw a J6M series centrifuge but I believe that I know what your problem is.  You have programmed a slow acceleration into the centrifuge by putting the value of 9 for the acceleration rate.  Clear that value out so that it is blank and then tell me how it performs.  Since you did not tell me what kind of samples you are spinning I have to say that with all due caution as if you are spinning blood samples then that acceleration rate might be too fast such that it would cause your blood cells to break apart prematurely.  Give what I said a try and get back to me.

Don

I cleared the accel display and ran at the same speed ( the rotor has only been run w/ buckets w/ inserts and no product through this whole time) and the time improved to 9 mins.I removed the inserts and was down to 7.5 mins. Seems to take a long time between 700 rpm to 1100 rpm. There is more shaking during that time, I know that it's level and the spindle looks straight- how long should it take to reach 4k under these conditions?

Thanks Don

Nice to know that your acceleration times have improved at least a little bit but the times are not out of line for the centrifuge/rotor combination you are using.  The JS4.2 rotor is one of the heaviest rotors that can be run in that centrifuge so you will probably see the time to 4K go up when you add samples to the rotor.  I really have no idea as to what you can expect as to the time to 4K with a fully loaded rotor but there appears to be nothing wrong with your centrifuge.  What you are seeing between around 700 to 1100 RPM is perfectly normal although you can minimize this by leveling your centrifuge with the lid off of the rotor and and the tie down removed, too.  Place a level on the center of the rotor and get the best level you can realizing that you only have 2 leveling feet whether it is front to back or more likely left to right.  Unless you have a perfectly level floor you just have to make the best of it.  The reason for the vibration is a physical property of a spinning rotor known as precession.  It is more pronounced in your centrifuge because of the time it takes to get through the critical speed zone but again, this is normal.  If you are going to be spinning blood samples in that rotor then you may have to make adjustments to the Accel and Decel settings to minimize issues with the separation of the products.  There is NO absolute cookbook on this although there are references available hopefully still on the Beckman Coulter website.  Hope this helps with your concerns.

Don

Hi Don,

The time to reach 4k rpm went down to about 3 to 4 minutes after finding 1/2 inch of water in the bottom of the bowl. We celebrated till we started getting a speed error around 2.5k rpm and unit is not consistant, ex. Sometimes it reaches set point at 4mins or 9mins or a speed error. While shimming one back wheel because the floor is not level from side to side, found that the spindle has a barely noticeable bend- could this be the cause for the inconsistency?

Removing your rotor and drying out the chamber should be a regular part of your maintenance of your centrifuge to prevent the kind of problem you saw. The surface effect drag on the rotor by the rotor is a real thing and I have actually encountered J6 series centrifuges with over an inch of water in them. The fact that your floor was so un-level may be the reason why your spindle has a slight bend in it and yes, that "could" be the cause of your issue. The spindle probably got the way it did by the centrifuge previously not being leveled properly and bent slightly to compensate for the fact that the rotor wanted to spin on the level. I suspect that you may indeed have a spindle issue in that the magnet secured to the bottom of the spindle could be loose. You should check to see that the allen head screw is positively securing the magnet so that the hall effect sensor that is mounted on the small arm under the spindle where the drive belt is located can read it properly. There are other things that can cause speed diagnostics but I am on vacation until March 12th so I have no reference materials available to me. Quite frankly, you are probably going to need service in to positively identify your problem if you can't wait until I get home. Sorry to not be a greater help right now.

Don