Morris,
If something had come loose inside the CRT wouldn¡¯t we expect that the symptoms might change with orientation? I haven¡¯t tried rotating the instrument (which is more difficult for you than for me), but I have tried tapping the case to see if the distortion moves (it doesn¡¯t, but I wasn¡¯t tapping very aggressively). I will try operating the scope horizontally as well as vertically and see if that makes a difference (which would, I think, confirm the hypothesis of CRT damage).
I¡¯d really like to see some pictures of what your 7904 is doing, just to verify that we are seeing similar faults.
¡ª Jeff Dutky
