It is not impossible for one Mac monitor to affect the display of another close-by monitor. For example, I have six Macs sharing a shelf, with only just over an inch between their bezels, and four of them are Compact AIOs. A IIci's active Portrait Display next to the Colour Classic causes sync. discrepancy bands to move up the CC's display. The CC's display affects the adjacent Classic II's display in the same way, and so on. It's not a large concern because I seldom have all of the Macs active at the same time, but it is as well to be aware of the potential for interference. The remedy is greater separation.
The screen burn-in has already been mentioned to you. The only remedy, if it bothers you enough, is to replace the affected CRT. If the burn-in is confined to the menu bar, it should not affect your convenience of use of the affected Mac.
Mac128 has also pointed out that 'image shows sometimes a little disturbance' is not descriptive or specific enough to be able to offer you any advice, other than the generality that electron beams (such as that which draws the display on your SE/30's screen) can be deflected also by interfering fields and faults in the driving circuitry. The symptoms may be diagnostic if you can describe them.
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The screen burn-in has already been mentioned to you. The only remedy, if it bothers you enough, is to replace the affected CRT. If the burn-in is confined to the menu bar, it should not affect your convenience of use of the affected Mac.
Mac128 has also pointed out that 'image shows sometimes a little disturbance' is not descriptive or specific enough to be able to offer you any advice, other than the generality that electron beams (such as that which draws the display on your SE/30's screen) can be deflected also by interfering fields and faults in the driving circuitry. The symptoms may be diagnostic if you can describe them.
de