Re: Old exam paper
I think a current tracer was some kind of magnetic pickup probe which you could align with a pcb track to see how much and which way the current was flowing along it. It would be especially useful for finding which of the many devices across a supply rail had gone short-circuit or low resistance without having to cut tracks.
I had a case several days ago where an old PCB full of soldered-in logic ICs clearly had one or more ICs short-circuit, so I could have done with one of those. I had to do it the other way - desolder the onboard 5V regulator (which was going into limit) and apply 5V power from a very heavy bench supply, ramping up the current limit until one of the chips started to get very hot.
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