...where it might have helped.
Two come to mind at least from late 1980s when I was working as PC support for a University. Both cases are ones of "That is just not possible, but it is happening.."
Case one: Screen going crazy, but not when I was in the same room.
Got a call that one of the screens was flickering like crazy so I went to look.
To visualize the place: the room was fairly long and narrow, with a small vestibule in front and thus double doors with about 1 meter in between. The inner door had a big glass window, booth doors were wood doors and such.
As I went to the room, the user said that the flickering just stopped, so I tried to look around a bit like checking that all cables were correct and such.. but basically shrugged and said that there was not much I could do and to call me when it happened again.
As I stepped out of the room and closed the inner door the use yelled after me that it started again, so I turned around and stepped back in... and he said "it stopped".. hmm..
Trying a few times(5-6?) just on a whim I stepped back and forth in the doorway and when the inner door was closed with me not in the room he said it flickered, but with the inner door closed and me in the room it did not flicker..
And by looking at the computer screen from the vestibule with the door closed I could actually see the flicker so it was not just the users imagination.
*sigh* So I puttered around a bit more and could not find anything. But as I the end I did not find anything and said that I could not do anything else..
A bit later I got a call that it had not flickered after I left that time.. So what caused it, probably some sort of interference from somewhere totally different and it just happened to match so perfectly those 5-6 times.. but the odds against such are pretty low, so..
Case two: The missing big Z.
Got a call one day to come and check out why they could not get a big Z to print.
I went to the location and true enough, there was a document written in word(the ms dos one) with a Z at some place in a math formula and the corresponding printed document that just had a blank at that location.
I went though the normal basic troubleshooting steps:
-Replace the Z with a Y in the same location in the formula->worked fine. Replace back to Z->nope.
Make a new document with many Zs->none of them came out
-Try a small z->worked fine.
-Do the same from Edit instead of MS word->worked fine!
Ah! I though something with word
-So I reinstalled word->same problem
hmm.. Ok, so lets isolate the problem.
-Move the printer to another computer->Same problem.
-Check another printer of the same type in the original place->everything works.
Hmm.. so the printer cannot print big Z from word but can from edit?
So I started playing around and suddenly the printer could print big Z after some trying around.
When thinking about it I noticed that I had actually switched the centronics cables between the printers.
-Switching back to original: nope no big Z.
-Switching to other cable: works.
Ok.. so how can that cable not print big Z.. so I tried it in in the other computer that had the same type printer and it worked.
Tried switching back and forth a few times and indeed: that combination of cable and printed did not print out big Z, switching the cable between that printer and the other printer of same type and both worked fine..