Hi, all of you. I've been working with this scope for a long time now, but lately I noticed that channel one was a bit unstable. Consequently the problem evolved into having ranges of 5V and larger not working at all. The scope internal relay is working as I can hear the click and compared to channel 2 it is switching at the right range change, however the display goes to a flat line at the 5V range. Anyone can help please?