That said i d also like to note that there are certain capacitors that just seem to spring leaks and the electrolyte can be corrosive to the board.
Bad capacitor leak.
I have seen that as well but didn t think of it when writing the posts.
The vent is stamped into the top of the casing of a can shaped.
Then you may see this brown crust around the capacitor or perhaps on it.
It often looks somewhat like a dried coffee stain.
When the capacitors are replaced the electrolyte can be cleaned up with a cotton swab and some isopropyl alcohol which will not damage components as it will evaporate.
Bulging of the vent on top of the capacitor.
Broken or cracked vent often.
In this image i have tried to photograph the slight bulge on the top of this bad capacitor.
Well bad caps typically have a domed or swollen top.
When examining a failed electronic device the failed capacitors can easily be recognized by clearly visible symptoms that include the following.