SPEED ERRORS

Speed diagnostics were not uncommon in the J2-MI series centrifuges and the cause of the diagnostic can be caused by several things. The first has to do with the tachometer signal. On the connector that attaches to the pickoff located on the base of the spindle assembly, reading between pin 2 and ground you should see the voltage alternate between 0 and +5 volts. If not then you probably have a bad sensor although I did see a few cases where the magnet attached to the bottom of the spindle actually cracked and fell away but that is rare. Then, check on pin 2 to ground on the 3-pin connector attached to the drive motor which is where the tach signal is generated. Again, you should see 6 pulses for each revolution of the spindle but the voltage here will be 0 to +12 volts. No signal or poor signal will mean a bad tach sensor on the drive.

The next item could be with the inverter chassis itself. Take a look at the three switch boards. You should see the LED's flashing off and on. Also, on the switchboard control board, there is a push button switch that when pushed should generate a reading of 220 RPM on the speed display and the LED's should stop flashing off and on.

You can also have a bad SCR pack on the chassis as well as fuse F101 being blown. There were also incidents where the soldered leads on R106 actually broke loose causing the problem. Another old one was the drip pan chafing on top of the large filter cap on the chassis.

I have given you a lot of information so check some of this stuff out and get back to me.

Don

when turning the rotor by hand the tacho signal is present and rpm display is seen on the top panel.

the 3 inverter pcbs have leds flashing but dont go solid when the m/c starts up, when pressing the switch on the control board you get 220 on the display, and the lights go out, inverters OK?

the fuse on the chassis is ok.

can the control board be bad? is there any way to check the SCR which i presume is on the mother board which the 3 inverters fit into?

all the cable connections looked ok on the chassis. i noticed that the solid state relay on the back had 240v on the output but not 32v dc on the input, is that relevant?

are you ex beckman engineer as i sometimes come across other issues on beckman m/cs

thanks for help so far

is R106 on the chassis at the back behind the 3 inverters? can the SCR be replaced separately or do you need to replace the complete bottom board?

jams

I will get back to you with some more info shortly but the quick answer is that yes, you could have a bad control board but I can't say that I ever replaced one in my 32+ years wprking for Beckman. Like I said, more to follow later today.

having read other posts i wonder whether the door lock is an issue, when manually activating the lid switch under the cover and pressing start i get a door lock error i havent checked the other lid switch where the actuator is, maybe thats an issue but would that not come up with a door fault first?

on the control board the red led is lit when the inverter pcbs leds are flickering.

could it be a bad fuse even though it meters ok?

cheers

jams

Thanks for the input Jeff and I guess that I assumed that everyone knows that you only check fuses out of circuit. Yes, the SCR pack can be replaced separately and R106 is on the chassis. It rarely failed but when it got real hot, for some reason the solder conncetions crack.

Don

Again, do not trust ANY reading you get with the fuse still in the circuit. Yes, door latch issues can cause problems BUT you would probably receive a door diagnostic if that was the case.

Hi i will be visiting next week so was wondering whether there is anything else to check, i will replace the fuse anyway. i was wondering whether you have any manuals that we could get as we often get issues with beckman centrifuges and stuggle to to help. we would happily pay for them if rquired

thanks

I am away from my home right now and won't be back for a few days so I will check my manual again at that time. As to my manual, it is somewhat old and does not have all of the latest electronic service memos which I have had no access to since I retired. They are helpful but far from complete and if I sold them I would be without the means to help others.

Don

Hi

Thanks for the reply. I understand about the manuals, didn't know if you had them on disc or not. Do you know of anyone in the US that would be able to offer training courses on the Beckman centrifuges?

Thanks

jams