OVERLOAD problem in Multiclamp 700B

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sharmakaushikp
sharmakaushikp's picture
OVERLOAD problem in Multiclamp 700B

I am using Multiclamp 700B and pCLAMP10 for my extracellular recording experiments. In current clamp mode, but with I=0, I use a gain=1000, and Feedback resistor Rf=500 Megaohm. Under these conditions I get an OVERLOAD error in Multiclamp Commander window. with no traces a all in pCLAMP or traces with very extremely high noise levels. However the same conditions had been working well in another setup having the same instruments. I have verified this setup using the Model cell (Patch 1-U Model cell, Bath configuration). After a value of gain more than 100 in current clamp mode, it shows OVERLOAD. Also, in Voltage clamp mode, with Rf=500 Megaohm, it shows overload even with a gain value of 10. I am not able to identify the problem. Please give me some suggestions.

vilsy
vilsy's picture
I am using MultiClamp 700B

I am using MultiClamp 700B too along with pClamp 9.2 though for my recording experiments. I=0 mode in the command software is not the current clamp mode, its an automatic switch mode where you can define on what conditons the cell is to switch from VC to CC or vice versa. Overload basically signifies the saturation of the internal circuitry of the amplifier. Thw way to tackle this is to reduce the Output Gain to say 100 from a 1000. Ideally it should solve the problem. If it does not try reducing the feedback resstor value.
When u say u cannot see on the pClamp it means its beyond the scale that has been defined by the telegraphs from the 700B. The large noise is something i cannot think of. I would recommend checking the grouding of the headstage to the solution and making sure that there are no junction potentials. Hope this helps