AKTA FPLC Mixer 925 Problem and Solution

[Han]

Chalmers <chalmers from nottingham.ac.uk> wrote in
news:mailman.308.1258476303.1133.methods from net.bio.net: 

> This is not exactly a method but could save you money.
> 
> We have an AKTA FPLC with the Mixer 925 unit.  We don't have a service
>  contract so when the mixer unit stopped working and the system  
> provided a short-circuit warning message, we asked the price of a new 
> one.  We were quoted £10,000, which is half the price of the whole  
> system.  Presumably this is a joke, designed to force you to call in  
> the engineer and then get a service contract, perhaps.
> 
> The mixer is basically a magnetic stirrer.  I opened the unit and  
> found a little 12 V DC motor that turns the magnet.  I was confused at
>  first because it worked when I attached a 9V battery.  The final  
> explanation was that the motor had difficultly getting started,  
> particularly at 4 C, but not so bad at room temperature.  It worked  
> intermittently for a while then failed.  It had only 2 ohms resistance
>  between the terminals (I suspect it should be 12 ohms).
> 
> The ID numbers on the motor specify a custom motor supplied to the  
> AKTA manufacturers, so you can not buy one.  However, it looked  
> suspiciously like a Premotec 990412018105.  You can buy one for £47  
> from RS components (the name on the motor is different but the  
> manufacturers product code is identical).
> 
> The Premotec motor is rated to run at 3600 rpm at 12 V.  However, it  
> receives only 1.89 V from the Mixer 925 unit.  It therefore runs close
>  to the specified 600 rpm when drawing power from the Mixer 925.
> 
> It takes about 5 minutes to change the motor using simple tools, and  
> we saved a significant amount of money.
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Thanks.  This is from home, and I don't know by heart whether we have 
that system, or another.  Neither do I know whether that motor would be 
available in the US.

I do know that I could replace the power supply on the Compaq computer 
that runs our HPLC after it quit.  About US$38 on Ebay.

-- 
Best regards
Han 
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