If it's old and nothing is a charred wreck I always start by looking for aluminium can electrolytic capacitors. They vent and eventually dry out, crummy but so much cheaper than tantalum bead you can see why they get used. Fortunately they cost pennies so it's a good place to start. I fixed a BMW once by changing one capacitor, I used to fix computer monitors before they went for an external PSU's, simply by changing electrolytics.