I want to use a Differential Scanning Calorimeter (DSC) to determine when my protein unfolds as you increase the temperature in a DSC machine. The machine is pressurised (to 3A) during the run, so samples won't boil when you scan from e.g. 10 to 100$^\circ$C. Lately the machine fails to hold the pressure after running one scan from 10-100$^\circ$C and back from 100-10$^\circ$C, when starting on the third round (10-100$^\circ$C again). Furthermore, the instrument claims to have both the sample/reference cells at 140$^\circ$C, in addition to the heating jack also claiming to be at 140 $^\circ$C after failing to maintain the pressure. I have lubricated the o-ring and changed the filters under the machine (did not help). Furthermore I plan to purge the machine over a weekend and refill it with nitrogen gas, but I'm not sure this will solve the problem as it seems to be related to cooling (?).
Our model is: TA Instruments Nano DSC III (model 6300)
Its an older unit, probably from around 2008 (Im not sure).
Here is an image from our lab:
Any ideas are appreciated.