looking for help with my PicoScope 2006. Channels A,B do not respond to input. I tried connecting the signal generator to channel A with no response. Channels A, B are "active" i.e. the signal line is moving, with a very small amplitude ~1-2mV. I use the scope to check the output of a current source, max load voltage ~2V. It was working last week but seems to have stopped. Any suggestions appreciated.