Okay so i got given a *really* old oscilloscope (like seriously, from 1940-something) and at first i thought it was working perfectly. But then every so often the line on the screen gets really shaky and jumps around a lot, as if there's a dodgy connection somewhere (and persists for a good few minutes before returning to normal again). I bought another probe because I thought that there was just a bad connection in it, but that didn't solve the problem. I have yet to open the scope up and look inside, but I would imagine this is a fairly common problem and was wondering what the most likely causes of this would be that i can look for?