Beckman J2-21m issue
I know I have an old unit but I service equipment for several labs and I get quite an array in type and age. I have serviced several J2-21 units but this is one I have an issue that has me perplexed. The motor does not run. The unit has another problem with the dorr latch. The latch has what looks to be a safety catch solenoid operated. It does not release the door because it doesn't seem to engage. Could this be the issue with the motor as well? Can some one tell me the quickest way to get to the solenoid so I can test it? Is this something that can still be purchased? I would like to replace it with something identical or approved by Beckman. Thanks Jeremy
The door latch is actually two interlocks in one assembly and if both switches do not actuate properly then the motor will never even start to turn. There is also an approximately 10 second time frame in which the rotor must start spinning or the start up sequence times out. There is the microswitch that you can actually see that is actuated by the eyebolt closing down on it when the door is closed and frequently it is just a matter of adjusting the position of the switch itself or replacing this switch because of damage from the constant banging of the eyebolt onto the switch arm. Try adjusting the switch first. There is also a microswitch that rests underneath the top cover that you can't see even if you remove the cover plate over the door latch itself. By the way, be very careful with the hardware as some of the small phillips screws are made from very soft metal and can strip very easily.
First, there is an updated door latch assembly and obviously I don't know which style you have installed on your centrifuge. One possible visual clue is the presence of two emergency access holes on the right side of the top cover along where the door latch is installed. Two holes indicates a new style latch because when the updated latch kit was installed it required a new accees hole be drilled.
So, to get at the latch itself you need to release the top cover and this is impossible unless you know that there is a bolt that comes up from underneath the right front cover of the centrifuge. Drop the lower front panel and you will see a triangular access hole at the right front ofthe centrifuge. At the top of the hole, a tight fit for almost anyone, is a single hex head bolt. Remove the bolt and you can then release the corner of the top cover AFTER you have loosened and removed all of the latch hardware that you can see. Once everything is loose, the cover can be pried up and you can get access to the latch. The latch pulls up and out and you must be VERY careful with the reinstallation of the latch because the wiring has to fit just right. Otherwise it will get pinched when you tighten the top cover down and may actually short out. Had it happen once in my career and never made that mistake again. Good luck with this and let me know if you have any more questions.
Don, Thanks for the quick reply. I hope I have the opportunity to help someone else on this site. I checked the door latch and found out it was recently replaced. It does not have a second hole drilled into the side so I think it was replaced with the same or original part. The solenoid still does not activate and of course the motor does not run. I would like to ry and approach this as if there was no issue with the latch. What would I look for if the motor simply did not run? The unit seems to go through the routines fine but I get the SPEED error when the motor fails to start. If I turn the shaft by hand I can simulate the motor and the tach reads fine but of course it still fails because I cannot maintain the speed accurately. By the way, I can do this because I hold down the micro switch in the door latch system. If possible can I get some type of schematic? Is there something simple I should be checking before digging into all the electronics? Thanks again Jeremy
Jeremy, there are no old latches available anymore. More than likely the engineer forgot to drill the access hole which will only be a problem if the door latch locks up. Then that hole becomes significant to release the latch manually.
The micro switch that you can easily see when thd latch cover is removed is typically the problem with what your are describing. There's not a lot of adjustment for the switch and usually raising the switches vertical position fixes the problem. Sometimes you also can move the switch closer to the eyebolt contact area by moving the entire switch mount towards the front of the centrifuge. Bottom line is that if the switches are activated properly, the 10second spin start up sequence starts and the rotor should start spinning. Try adjusting the switch and get back to me.
jeremy, in such case, you need motor oil to smoot it for keep running.
I am working on a J2-21 and I was replacing the power switch/breaker. The older one has an extra post labled Auxiliary coil this is absent on the new one. I checked continuity from each post to the extra and I get nothing no matter what position of the switch. I have a few questions:
Can you tell me the wiring scheme and why there is a difference?
Do I need to replace it with another similar one and if not what do I do with the extra wire?
If there is no continuity, is the the issue?
Thanks again for all your help.
It sounds as if you had the incorrect circuit breaker for a different model centrifuge already installed and it apparently worked OK. The correct breaker for the J2 series centrifuges should not have the extra contact which is meant for centrifuges with a cover interlock switch and the J2-21 series did not have this switch. Beckman started using the breakers with the extra contact on the circuit breakers on centrifuges after it was discovered, (like it took over 50 years of manufacturing to figure this out), that customers were removing covers and exposing themselves to potentially lethal voltages if they touched someplace accidentally. Therefore, with the interlock installed, when the front cover was removed the AC lines were kicked off.
The breaker you have should work just fine. Just hook up the line in and out wires correctly and you should restore normal operation to the centrifuge.
What I did was just as you said. I taped off the extra wire that the new switch would not be using and installed the switch with the 4 primary posts. This brought me back to my original issue.
First I want to thank you for your patients and help with this unit. In a normal situation I would consider this unit not worth repairing due to its age but the situation makes it difficult to walk away from. When I originally contacted you about this problem I do not know if I was clear on the symptoms. The unit acts and programs normally. The two symptoms I can tell you are:
The solenoid on the lid lock does not activate allowing me to open it. And the motor does not engage so the program fails on a speed error. The reason I tell you both of these is because I am looking for a common issue tied to both characteristics. If I can narrow it down to one problem source I think I can run down the issue.
As far as the door latch micro switches, both have been tested and they work great. I just get no juice to the solenoid.
Thanks again for the help.
Jeremy, I guess that you confused me a little with your post that said it was a J2-21 when in reality it is a J2-21M. You really should have the breaker with the extra contact.
The fact that the door latch allows you to open the door with the power on means the solenoid is actually engaged so there is power to the latch. When you hit the start button, the latch power is released and the the springs that are part of the latch should force the latch closed thereby activating the rear switch under the top cover. The eyebolt attached to the door activates the other micro switch attached to the frame under the latch cover. If either one of those is not activated properly then the centrifuge will never start. Does the door latch actually lock when the power is turned off? If not, then you still have a problem with the latch assembly itself. If the latch is removed and not reinstalled properly, you can actually get some binding of the latch assembly thatwill not allow it to function properly. Otherwise, it just sounds as if the command to start the run is not getting the job done to release the latch and allow the drive to spin.
To me, it sounds as if the common issue is the fact that the door latch is not locking after the start button is pushed. That will NOT allow the drive to start spinning which will then give you the speed diagnostic.
Get back to me when you can.
The solenoid does NOT energize. The only way I can open or close the unit is if I manually push the bolt lock out of the way.
This is why I believe the two issues are related. When I manually close the door and press START, the unit fails with a speed error because the motor does not start.
As far as the breaker switch is concerned I will seek out a replacement switch that has the auxiliary coil post.
Jeremy, When you say that you manually push the bolt out of the way, how are you doing this action? Again, if the latch is not functioning correctly then the drive motor will never start. The electronics was designed in such a way that if the status of the two door latches is not detected correctly, the drive motor will NEVER engage. We need to get the latch issue solved first.
In my very firstresponseto this issue, I described how to release the top cover assembly after loosening all of the door latch hardware. I forgot, howeverr, to specifically mention removing the two screws that hold the latch release handle to the latch assembly. You need to remove them before you try to raise the top cover. So, you need to make sure that the latch cable has not become disconnected from the cable that runs up to it. There were also a few centrifuges that went out the door with an extra cable inside of the right corner chassis because the original cable was made too short. Check that too and make sure that if it's there that it is connected properly. It has been awhile since I worked on one of these centrifuges but I seem to recall that the relay that actually controls the door solenoid operation is on the low voltage power supply assembly. You will have to trace back to that point to make sure that the relay is working properly too because that could very well be the source of the overall problem .
Again, get back to me when you can and we'll go from there.
Starting with the latch assembly. I have already removed it before when I tested it. The latch assembly has two micro switches wired in series. I tested the integrity of both switches and they operate fine. In order to open and close the unit, I had to drill the hole in the side of the unit near the solenoid to push the rocker arm out of the way, so the bolt could spring back.
The fact that I have to push the rocker arm out of the way is because the solenoid does not activate, therefore the rocker arm does not swing clear of the bolt.
I am not doubting the problem may be in the latch assembly. One of the biggest problems I face is I have no schematics so I base most of my theory of operation on what I see and logical interpretation from that.
So if the door latch solenoid does not activate, then it isn't getting voltage. Then the door remains locked. However both microswitches would remain compressed putting the unit operational state. The only feedback the solenoid can give is the microswitch position.
Perhaps there is a way to by-pass the whole latch assembly to determine if it is the cause of my motor failure. I have 4 wires coming off the latch assembly, two for the microswitch series, and 2 that energize the solenoid. The only 2 I would have to alter would be the switches. Is this a correct assumption.
Didn't have time to look at the entire thread and read Don's excellent inputs, as always!
Just a quick suggestion. - have you checked the fuse on the main board, which is often a culprit when the door latch doesn't trigger?!
All the best. R
I realize that troubleshooting without having ever seen a schematic is at the very least problematic. That's why I tried to give you as much detail as I could from my own failing memory. Your logic is sound, however, the bigger issue is determining WHY you have no power to the solenoid. Fix that and everything else should fall into place and restore normal operation. Raj had a very good suggestion so before you do anything else, trace back to where the cable for the latch goes to and figure out why there's no power getting to the cable. You did actually verify that there's no pwer going to the latch didn't you? I have seen latch solenoids fail but if there's no power then that should be the very first thing to work on because normal centrifuge operation depends on correct latch operation.
My name is Varghese. I would appreciate if you could share with me the part number for the lid microswitch (Beckman J2-21) and where can I buy it?
I seem to be having a smiliar problem with my J2-21M centrifuge.
- Motor does not rotate after pushing start - gives a speed error after 10 seconds
What I have checked (I am fortunate enough to have 2 of the same model; 1 which works 1 which does not. Most of my testing has been done by replacing parts):
- Motor is operational, checked against working centrifuge
- Motor recieves power
- Latch assembly works fine (both the one hit by the eye bolt and the solenoid that acctuates when the centrifuge is started)
Is there anything else that I should check?
Check the obvious first; unplug, open the front panel and check the belt to see if it has slipped off of the pulleys or has broken. If the belt is ok, check that the motor's tension spring is intact and still doing its job.
Belt is in good shape.
The motor tension spring is in good shape as well.
I have found that the micro-switch contact arm, at the base of the motor, sometimes needs a slight adjustment in order to attain proper motor startup. If the contact arm is in a position where it is on the hairy edge of open/close when in contact with the motor frame, the slightest movement of the motor housing will open or close the switch and shut the run down immediately and give a speed error. Have you tried very slightly bending the contact arm in or out to find the proper position?
I have not tried bending the contact arm but I will try.
It is the J2-21M.
I thought that you had a J2-21, not a J2-21M. I've been giving advice based on the J2-21. The M series has a much different motor configuration. If I remember correctly, it has the induction motor, not the brushed, spring tensioned motor/housing.
That is correct, it has the induction motor. I had first thought to replace the brush but noticed it did not have one.
To clarify a few points for all, even the J2M series have a spring loaded motor albeit an induction drive motor. Also, in almost 33 years working for Beckman, I never had a drive spring cause any problems with motors not turning.
Now, to the speed diagnostic, when you have the lower front panel off, look at the pull out chassis and tell me whether or not you see the LED's on the the three switch boards turning off and on. They are controlled by the the other circuit board found within the chassis. There is a push button switch on that circuit board. Push it down and the LED's should all turn off except one that will be on steady and the speed display will show 220 RPM. So let's start from there. If you don't see them cycling then that will be the focal point of figuring out what is going on.
all the LEDs are cycling on and off. When I press the button all but the lower left light turns off while the lower left light is solid. The RPM shows between 220-230
To clarify; all of the LEDs turn off except for the lower left light which remains on.
It sounds as if all of the switch boards and control board are working properly. There is a fuse on the slide out chassis so make sure that it has not blown. There were also problems where the the soldering on the large vertical resistor got so hot that the solder melted and opened up the joint which also caused problems. I am on the road until at least tomorrow so I will try to get back to you either later tomorrow or Saturday after you get back to me.
I believe it is something wrong with the control board. Like I mentioned I have 2 of the same model units to work with, so I replaced the whole slide out chasis with the working unit and it ran.
However, I was not able to determine what is actually wrong with the other one. I inspeced the unit and did not see any solder melted. There was however some black undernearth the slide out chasis where 6 of the connections were.
Not sure if that is my problem or how I would be able to troubleshoot further.
If you believe that it is the switch board control board then swap it out from the known working chassis. That is the quickest way but the fact that you are seeing some charring on the chassis has me more concerned. You may also have a defective SCR pak which would definitely cause your no run situation and I would lean towards that before there being a problem with the control board. Can you be more specific as to where the blackened connections are at on the slide out chassis? A picture would help.