unit keep trying to speed up but won't goes pass 6000 rpm with 12 sample tubes loaded

update to the information above.  i ran 12 sample tubes of 7ml on 70.1Ti rotor, it works fine.  so i filled them to full tubes (10ml) in all 12, this time it cannot pass 25000rpm.

Anytime an L8M could not get up to speed it was typically the result of a bad section on one of the 3 switch boards that control the drive voltage.  That, or poor vaccum can cause a rotor to not get up to speed.  The vacuum should get down to less than 20u's in less than 20 minutes.  If it cannot get to that level of vacuum then that is where you need to start looking as to why that is not happening.  Old vacuum pump and/or diffusion pump oil can be an issue.  A bad diffusion pump heater can also cause poor vacuum performance.  Cracks in the vacuum hose also have to be checked for along with accumulated debris around the top of centrifuge vacuum cylinder.  As far as the switch boards are concerned, remove the front cover and slide out the electronics chassis.  Instruct the centrifuge to perform a run, so obviously a rotor needs to be in place.  Watch the LED's on the 3 switch boards and make sure that they are cycling off and on.  If they are not doing that then that is where your problem lies.  Get back to me when you can.

Don

thank you very much Don,  i replaced board #6 and that fixed the problem.

Trong Ha