Hello / B. Braun Thermomix

Hello all,

I just formally joined the ranks of sous-vide enthusiasts this week by picking up a used Thermomix 1420 on eBay. I have seen this bad boy on laboratory surplus sites for $500, but somehow I managed to snag it for $65 including shipping.

My challenge now is that this unit is long out of production (it was manufactured in West Germany if that tells you anything) and there seem to be no manuals anywhere. There aren't all that many Thermomixes in use at all, let alone this exact model (at least for culinary applications), and so it's been tough to learn any tips/tricks particular to this unit.

(Btw: this is NOT the unit incidentally of the same model name manufactured by Vorwerk; this is from B. Braun, a manufacturer of medical/laboratory equipment. It looks like this: http://www.biosurplus.com/store/products/5012455-b-braun-thermomix-1420/)

I've tested the temperature sensor calibration and it is dead on, even after 23+ years in a lab somewhere, so I was pretty pumped about that. Beyond that, though, I'm just wondering if anyone has experience with a Thermomix and can contribute any wisdom. More specifically, what is the left knob?? It has four positions: V, 25, 30, and 37. Weird, right? As far as I can tell, it doesn't seem to affect thermal output, and it doesn't change the sound the pump makes. I'm stumped.