Techne Gene E thermocyclers

Jim Owens jow at helix.nih.gov
Tue Nov 29 11:36:24 EST 1994


In article <shopkins.3.0011B9E4 at fs1.ho.man.ac.uk> Steve Hopkins,
shopkins at fs1.ho.man.ac.uk writes:
>the various options provided by different manufacturers. If there is
anyone 
>out there who has identified an optimum method I'd like to hear of it,
as well 
>as any difficulties arising from this issue (irreproducability, block 
>inhomogeneity etc).
>Are heated lids a real bonus, or do they provide another source of 
>inhomogeneity?

We have an MJ Research cycler with a heated lid and an in-sample
temperature probe.  Things worked well for three or four months before a
problem developed.  The cycler is designed to set the timing of each step
either from the block's temperature or the in-sample temperature probe. 
I always used the in-sample temperature because that is the way our old,
faithful cycler (Ericomp) had worked.

The problem that occured was that the cycler would slip from using the
sample probe to the block's temperature without notice.  Right now the
cycler is back at the manufacturer for repair, but I got an interesting
response from an MJ Research employee to an e-mail message about my
problems.

It stated that the in-sample probe would be less accurate with a heated
lid (changing the resistance of the wire attached to the temperature
sensing element).  The suggestion was to rely on the block temperature
rather than the in-sample probe when using the heated lid.  The switch
form in-sample control to block temperature control was due to another
problem that was not allowing the system to get the temperature of the
in-sample probe to the set point quickly enough to prevent the switch in
control which is a built-in fail-safe control.

All _I_ know for sure is that my PCRs were working fine with the heated
lid for several weeks before the problem cropped up.

Good luck,

Jim Owens



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