A work colleague wanted me to test a pre-amp stage of a valve amp that he his currently working on.
I set my sigen up and wired it up to the oscilloscope for some benchmark readings. It all worked as expected, duty called and had to leave it until lunch before I could test the amp. I left the oscilloscope on connected to the signal generator. Throughout the morning the trace drifted vertically unit I couldn't adjust it down any further. it the continued to rise right off the screen. The trace now sits right at the top edge of the screen, just about catch the shadow of the trace if the intensity is turned up quite high.
My initial thought that something had over heated, so I turned it off for a couple of hours. This had no effect.
So the bottom line is the oscilloscope is broke. Has anyone had problems like this before or could anyone suggest any tests that I could perform to track down the problem?