SI ran my 2% agarose gel on constant voltage (100 V). For a few times it worked at CV but, after a week or so the machine would automatically switch to constant current by itself. And this only happens when I try to increase the voltage to 100 V. It works fine between 50-80 V. Beyond 80 V it keeps fluctuating between CV and CC.

Is there a problem in my power supply (GENEI electrophoresis power supply) or is the TE buffer that I am using? Although I checked its pH and it's fine.

  • $\begingroup$ Can you provide a few more details (you can edit your post to do so): At what voltage do you run you gels? How big are they? Which powersupply are you using? $\endgroup$
    – Chris
    Commented Apr 12, 2014 at 8:56

1 Answer 1


I haven't found a manual for this machine, but my guess is that you exceed the maximum current which the power supply can provide. This is something I have experienced myself for electrophoresis.

Usually power supplies then switch into the constant current mode at the maximum current they can deliver, which I think is what happens here. If the voltage you choose is lower, you do not run into this limitation, thats why it is working without problems.

So you can either run your gels at constant current, which makes them run faster but also produces more heat, which can make your gel blurry. Or you live with a slightly smaller constant voltage, have your gels run a bit slower, but probably have a bit better resolution. I have to say that I have never had any problems with the resolution, even when I ran my gels really fast.

  • 1
    $\begingroup$ I tend to agree with this answer. Another cause for exceeding the max current could be a result of both high percentage gel in combination with old buffer, each contributing to greater electrical resistance. I prefer not running the voltage too fast otherwise you lose resolution due to the additional heat that causes the superficial gel surface to melt, appearing blurry. $\endgroup$
    – user560
    Commented Apr 12, 2014 at 14:18
  • $\begingroup$ alright great. these days i'm sticking to a lower voltage itself so i'm not facing any problems. but i just wanted to know the reason why. thanks guys it makes sense now :) $\endgroup$
    – Fatema
    Commented Apr 12, 2014 at 14:21
  • $\begingroup$ Gel melt can cause relly problems with low melting agarose. I have seen this at a colleagues gel once.... $\endgroup$
    – Chris
    Commented Apr 12, 2014 at 22:00

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