Discussion Category:  Centrifuge

TLX temperature drops slowly

 Our TLX-120 recently showed hesitance in dropping temperature below 8'C or so.  It'd bring temp down from 22-10'C in the first 15-20 min then another 20 min to 8', and another ~50 min to 4'C.  When it started to run with a 4'C pre-cooled TLA100.4, the temp will go up 2-3 degrees more then drop slowly.  I think it is stable at 7'C with rotor running.  Did not try lower temperature as it took over 1 hour already.  Just a few months ago it was fine running at 2’C.  Anything I could try to improve this situation? 

 

I tried temp calibration 'enter 1 0 0 enter' but it did not do anything (no beeps, nothing).  Don’t know if I did anything incorrectly.

 

Thanks.

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LanceH
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LanceH

Don,

The story continues.

We called another service company who seemed to know a lot about the TLX. He replaced the 4 chamber ties, and secure the chamber just like what you said. He then turn on the power and the TEM did not seem to work. We tried reseting the power breaker on the board, same thing. He then measured the voltages on the power board underneath the display and said something wrong with the power. The 15V outlet read 26V. He happen to bring another power board and switched with the existing one. Same thing. I don't think he fully secured the tachometer etc before trying these (maybe hooked up) but be did not thing that's a problem.

Now he went back to check what could be wrong there. Have you seem this before?

When the first guy came the firs time, he also measured all the voltages on that board and said all were fine, maybe a little noisy for the 24V but was within the range. It's sad that all was working reasonably ok before I called for a pm.

LanceH

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dpkleessr

Lance,

   Sorry to hear that the saga continues.  You mentioned that the technician did not bother to secure the tachometer.  Did he at least make sure that the white ring with the four hex screws at the bottom of the chamber that is actually the temperature thermister was connected?  If it is not connected then you will not get the thermoelectric modules to work at all.  That white ring also MUST have thermal paste smeared underneath it to make a good thermal connection to the refrigeration can.  I also have to ask whether or not everything is properly reconnected as to all of the cabling that runs from the chamber, drive, and all of the control boards?  An unloaded power supply may read higher than usual but usually NOT by the difference that you saw.  Get back to me when you can.

Don

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LanceH

Don,

When the technician started the machine yesterday, the temperature display dropped from 23.1 to 22.9 in the first minute or two and stayed unchanged for a couple more minutes until the machine is turned off.  The drop was probably caused by vacuum but presumably the thermister was connected.  The tachometer (the last half-ring) was loosely placed at it's position.  I asked about it.  The tech said that he was just going to test if the TEM works. He is coming back on Monday.  I'll make sure that he has everything connected.

On the way out of the door, the tech said that he did not think the TEMs are bad, maybe there was a bad transformer.  I did not feel too comfortable about the latter part.  A bad transformer would affect a lot of things, I think.

LanceH

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dpkleessr

Lance,

    The slight drop in temperature that you observed was of no significance at all and was more than likely just as you supposed to the actuation of the vacuum system.  The fact that you had a temperature readout at all indicates that the thermistor was connected and the tach ring being loosely attached really has no impact upon the cooling system.  Again, without a hands on situation for me, I would say that there is at least one TEM's probably burned out.  That or there is a connection issue somewhere in the circuit for the TEM's.  I'm not sure what transformer the tech was referring to but if it was the main one then that would have greater implications than just the temperature control.  Did he check all of the voltages while he was on site?  There are test points on the power board that are readily accessible with the cover off for the TEM's not to mention other voltages.

Don 

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LanceH

Don,

Yes, he checked the 24V and 5V ports on the power board.  Both were fine.  Only the 15V ports read incorrectly.  I'd agree with you that transformer is less likely to be the issue based on this fact.  The reason he did not think that TEM was the problem was that he never saw one fail before. He did say that he had TEMS in his bag.  Maybe I should suggest him to focus on checking the TEMs when he returns on Monday. 

I recall that the first tech also checked all voltage ports on the power board and all were fine at the time when TEMs were working.  Perhaps something indeed happened to the TEM(s) when the first tech tried to adjust and tie the chamber with one hook.

LanceH

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dpkleessr

Lance,

    The other voltage that I was primarily concerned with was the drive voltage for the TEM's.  There is a test point on the board that allows you to monitor the voltage going to them.  You should also be aware that the uneven pressure placed upon one or more of the TEM's when the can was installed with only one tie down may have actually cracked one of them.  They have a ceramic coating on both sides of them upon which the thermal paste is placed and that ceramic can be cracked.  If one did get cracked then you are pretty much screwed until it is replaced and hopefully no other damage has been done.  I still believe that the other service company is responsible for the current condition of your centrifuge.

Don

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LanceH

Don,

I've complaint to the first company but their manager went by what the tech wrote which was what I told him (i.e.  the temp  dropped slowly between 8 and 4'C. ).   At  that time the tech even told me that the slowness was normal . Of course he did not write this part.  The manager insisted that it was a sign that the TEM was failing ...etc. The only thing I could do to deal with such a company is not to do business with them. 

I am guessing that the 15V the second tech measured was for the TEM.  I asked if that voltage would read differently if one of the TEM fail.  He said no.  Hope he will come up with a solution on Monday.

 

LanceH

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LanceH

Don,

Problem solved!

The technician from the second company replaced one of the TEMs with spare parts he had and everything worked just fine.  The machine cooled down to 2'C in 15-20 min, just like what it used to be.  He said he'd only charge a hundred bucks for this work.  It's like doing us a favor, I think.  I am going to recommend him to my colleagues whenever they have centrifuge issues.

The failed TEM was the one near the sole anchor of the chamber before all 4 were replaced last time.  It appeared to be cracked also.  Clearly, it was the result from  the work of first tech. 

I had a chance to take a look at the service sheet inside the machine.  The machine was mainly serviced by Rod Glenn from mid-90s to early 2000.  Do you know Rod by any chance?

LanceH

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dpkleessr

Lance, Pleased that your problem is finally resolved based upon what I told you that it most likely was. I believe that I would be in touch with that other service company and ask for a refund of their charges or at the very least, the costs for the repairs of the other company. If they have any integrity at all then they will work with you. Otherwise I would make sure that you tell your colleagues of the poor service that you received.

I know Rod Glenn as were in training classes many years ago. If he was taking care of it then the centrifuge was getting good service.

Please don't hesitate in getting in touch with me if you have any other issues with any Beckman centrifuges, spectrophotometers, or LS counters.

Don

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