I have recently acquired a Tektronix 454 off ebay and I'm having an issue with the trace flickering even if the intensity is turned up to full the flicker is noticeable and if the intensity is about half way the trace can completely disappear and come back. This seems to get worse as the unit warms up. I don't think this is an issue with triggering as the flickering happens even when I turn the tim/div down to 1sec/div the signal will flicker as the trace is going across the screen. There's also an issue with x,y mode where the trace will gradually climb the y axis to the point where the position knob cannot get it back.