Basic scope questions...

[Cqwet Dbdfte]

The tantalums on the 4XX series are all over the power supply rails, hundreds of them on a 485. They short to near zero ohms when they go. I ended up using a milliohm meter to zero in on the board to find the likely shorted one to minimize the work in pulling the various boards in the jam-packed cabinet. Wasn't unusual to find multiple shorted ones on the same scope, which means some probably went without power even applied.

Besides a milliohm meter, or a FLIR scope, a high resolution voltmeter can be used to chase down shorts on a PCB, by using a stable low voltage supply, like 1V, current limited, then look for millivolt differences between conduction paths, lower voltages points to the problem.