slow rpm

Basically, ignore the numbers on the speed knob of a TJ6 centrifuge. The maximum speed of any particular run is based upon how big the load is in the buckets. The TJ6 was one of the first benchtop cenrrifuges ever manufactured and as such it was also the most simplistic. The speed you see on the speed readout is all you get. There's no speed adjustment so that's why I say what you see is all you get. Unless the brushes are worn down to their wear marks, changing them buys you nothing. Burning smells are also not that uncommon because the rotor is just spinning against air resistance which causes a lot of motor heating.

Don

Speed of 7000 is achieved with the same load on four other identical machines. First machine motor turns hard by hand with brushes removed and belt removed also. Feels as if there is an internal obstruction. Second machine spins easily but seems to have no power. Am hoping a check up at a motor shop might solve a few problems with these machines. Can you recommend such a business where I could send two motors for a cleaning and possibly a load test?

While your at it could you recommend a more modern machine that would replace the TJ=6's in the lab? Hopefully something in a tabletop unit.

First and foremost, DO NOT run a TJ6 that fast.  You are dealing with a lot of very old metal in the form of your rotors.  If that rotor comes apart, and they do, you will have centrifuge and rotor parts spraying out around the room at that speed.  It is a serious safety hazard.  It has been probably close to 20 years since the TJ6's were even sold so again, be very careful with the speed you run any of them at. 

If the motor is that difficult to turn with or without brushes then you have a bearing problem.  It is possible that applying some penetrating oil of some kind may improve the situation but I would still be very guarded about a future motor bearing siezing.  I can only say check your local yellow pages for electric motor rebuilding.  Get an estimate for repairs and compare that to the cost of replacement of the motor if one is even still available.  Beckman stopped servicing the TJ6 series many years ago and went out of their way to purge old part stocks for obsolete products such as the TJ6.

As to a replacement centrifuge, that would all depend on what you are spinning, the types of tubes being spun, etc.  One of the better workhorse tabletop centrifuges are Allegra X22 series and the Allegra X12, 14, or 15 series centrifuges.  I only know about Beckman products because I worked for them for almost 33 years.  I'm sure that there's other good centrifuges out there.  I just don't know anything about them.

Don

My mistake,,,The machines target speed is 2700 rpms. Big difference huh? Anyway I'll rebuild the better motor of the two and see where it goes. The bigger Sorvals are the high speed machines in the lab. We now have three to five running Beckmans and two to three parts machines,,,maybe.

When it comes to replacement centrifuges I will only offer these words of wisdom; EVERY salesperson I have ever encountered will tell you that their companies products are the best and then offer a multitude of reasons why they say what they do.  If you really want to know who makes centrifugtes that will meet your needs now and probably into the future, get references  from your colleagues, NOT the salesperson.  Salespeople cherry pick THEIR references and provide incentives to customers that assist them in selling instrumentation.  Find out where competing centrifuges are and make some test runs for yourself if the owners allow it.  It's just like test driving a car and almost as expensive.  I may have retired from Beckman Coulter last year but I owe no allegiance to them.  Some of Beckman's products are great and others I wouldn't touch.  I have also had some of my former customers say the same thing about Sorvall, now Thermo Fisher.  Remeber, the people you will be dealing with are SALESPEOPLE and it's their job to tell you just about anything to get you to buy from them.  If I sound a little jaded about the entire sales process you would be correct.  In 33 years I heard things that mad me really disappointed that someone I worked with would say things that I knew the instrumentation could never do, and I'm talking about products other than centrifuges, too.

Don