What’s the first thing you check when a piece of electronics stops working? I bet it’s the power supply voltages and if you are repairing a board that’s over 20 years old then you’ve probably your share of tantalum bead capacitor failures. If you’re lucky they will just short out and current limit the power supply but I’ve also seen them explode into a small ball of flame! But whence the fail… the noise… the vile smell?