In article <7Kv9s.17694$nu2.12...@newsfe16.iad>, d...@no.email.thankstospam.net says... > > In article <mailman.710.1348792053.3456.meth...@net.bio.net>, "Phelan, Paul > J." <paul.phe...@tufts.edu> wrote: > >I think this will be an unusual question. I use a Biologic Duoflow > > chromatography system (from Bio-Rad) for a lot of protein purification, and > > lately I have had a bizarre problem with the system. The pumps have been > > starting by themselves, even in front of my eyes as I watch, and every time > > they start running at 10 ml/min., all by themselves. This has happened > > whether the software that controls the system is open or closed, so I have > > had > > to power off the pump station whenever I am not running it, to keep it from > > running by itself without warning. It behaves just fine when I am running a > > protocol on it, so at least I can still use it, but a few times when I left > > it > > powered on, I have come in to find a whole liter of water or buffer emptied > > into the waste, and the lines are completely empty. Yes I have contacted > > Bio-Rad about it, and the rep. said over the phone that she never heard of > > anything like that, but I haven't had anyone come out to look at it, because > > that costs a small fortune. The rep suggested that it could be due to > > condensation inside the pump station shorting out some connections, so I > > took > > everything out of the refrigerated cabinet where we keep it, dried it out at > > room temp. and it ran just fine (no auto-starts), but a while after I put it > > back into the cold, it started to run by itself again. I don't expect > > anyone > > to have a magical answer, but I wonder if anyone else has ever seen anything > > like this? > > Definitely a spurious electrical connection. My bet would be termal > contraction/expansion of a solder point that is about to fail (had exactly > the same with intermittently working car clock). There shouldn't be many > triggers that start the pump, so checking and perhaps lightly resoldering > all the suspects should in theory do the job. Taking it all apart is not > going to be fun... > > DK
Yes, I agree, some sort of "creeping currents". This can be caused also by an unclean electrical supply (with spikes from elevators, air-con etc.), and by dirt or other conducting material inside the unit. So the rep might actually be right. Do you use the system in the cold room, in particular, does it get moved between cold room and normal temperature -> condensation? I once had a spurious problem with an instrument whose PCB had not been thoroughly cleaned from solder flux... What I would do (or have an in house electronic maintenance unit do, as it requires some experience and a lot of time), is to disassemble the unit and clean all the parts (PCBs, switches,...) with water-free i- propanol (a toothbrush is very good for that sort of job). Allow to dry completely o/n. Obviously, that requires a good fume cupboard and precautions against ignition. Then check for "cold" solder-points, using a magnifying glass and a strong light. Re-solder anything that looks suspicious. Re-assemble and put a line filter between the instrument and the AC socket. With a little luck, that should do the trick. -- Car (noun): erratically moving obstacle on the road _______________________________________________ Methods mailing list Methods@net.bio.net http://www.bio.net/biomail/listinfo/methods
