calibrating gilsons

Peter M. Muriana muriana at
Mon Sep 26 08:49:56 EST 1994

In article <94268.001509U58563 at>, <U58563 at> writes:
>This isn't too sophisticated.  The main problem is turning the calibration
>control, which is the INNER ring as seen from the top of the instrument.  Some
>commercial person tried to convince me that you needed this special $600 steel
>gizmo (a rod with two prongs, in other words) from Gilson to do it (he was NOT
>use your analytic balance and your gizmo, and away you go.

	I just serviced our own Gilson/Rainin Pipetmen - I bought a (don't 
know the correct name for the pliers) set of pliers at an auto parts store 
($12.00; pliers come with several pairs of tips that get screwed into the
working end of the pliers) that fits the set holes in the pipetter.

If you are just a little off in volume from the numbered settings, you can 
fine tune by adjusting the small, inner black ring (with holes) at the base 
of the thumb button & rod with the special pliers (check as above using an 
analytical balance).  If you are way out of alignment, you may have to 
remove the inner black ring & thumb button, then remove the larger black 
ring (keep winding the number adjustment ring above its maximum volume and 
until it comes out.  You will then have to put it back into the chamber, 
but **loosely** and turn it so that the number settings change "without 
getting the assembly locked in" (we had to set the number settings on our 
1-ml pipetman to about 1.35 ml, then place the main number adjustment wheel 
back in place - by the time we screwed it in and the numbers were back 
around 1 ml, the pipettor was measuring out about 1.1 mls - we then used 
the inner set ring (with thumb button/rod attached) with the special pliers 
to fine tune it to 0.9985 mls (closest we could come without over/under 
shooting by more).  I know this description is hard to visualize, but it 
amazes me how all the "repair" places could charge about $50 for something 
which took me about 10 minutes to repair.

	The other most repairable problem is when the teflon/O-ring combo 
around the plunger (in the barrel) gets grit/dirt on them.  Since it's the 
rubber O-ring that provides the vacuum seal when the plunger is released, 
if it's dirty, you won't get a tight seal and may notice liquid dripping 
from your tips while you are trying to pipet.

Regards, Peter

>   Cleaning out your pipettemen from the inside is something you can try out
>for yourself also; it doesn't take any special care except NOT to lose the
>little rubber ring and white plastic disk (try a P1000 first, with p20's they
>are tiny!) I like to do it before starting pA+ RNA isolations, for instance,
>to be sure no RNase gets in that way.  The ring and disk are subject to wear
>and can/should be reordered/replaced eventually (like, when you start noticing
>that glycerol doesn't come in -- it means there's an air leak!)
*  Peter M. Muriana, Ph.D.		Phone	= (317)-494-8284	*
*  Dept. of Food Science		FAX	= (317)-494-7953	*
*  Purdue University		E-mail	= muriana at	*
*  W. Lafayette, IN  47907                                        	*
*	Disclaimer:  The opinions stated above are mine alone		* 
*	and do not represent endorsement by my employer			*

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