Trying to repair my 80's vintage function generator, an IEC F72. Found the 5V rail was low. Found it was actually shorted when I pulled the three terminal regulator and connected my lab supply and saw it current limit!! I have a schematic, and the board is a beautiful 80's through hole lab quality piece. The voltage rails are supplied through a few jumpers here and there, so I desoldered the jumpers to isolate the portion of the board with the short. Unfortunately, I isolated it to a still large section of the circuit, and nothing is getting hot!! Obviously, I checked the electrolytics, they are still fine. I tried using air in a can to put frost on the board and look for something warm, but I'm stumped. One difficulty is that the circuit branches to two subsections from the jumper I have isolated the problem to. I was thinking I could wind some wire around a piece of ferrite and use it with an oscilloscope to see an increase in potential and crudely determine which trace is carrying the several amps of current, and maybe follow it. Anyone have any experience or tips? Would that even work for detecting DC with sensitivity sufficient to track the current?
Thanks for any advice!
KI4TJ