Hi,
Just to note, removing a component from a double sided board is a little more complicated than with a single sided board. The double sided board has small 'vias' that run from one layer to the other, usually some sort of plating that forms a little tube that runs from the top layer to the lower layer. That forms a connection between the two layers. This is important because when you insert a large component like a capacitor, you usually can only solder the leads onto the bottom layer. The top layer gets it's connection from the metal plated 'via'. Without the via, the connection to the top layer would be removed and that could cause a break in the circuit and cause the whole thing to malfunction badly.
The problem is, when removing the old capacitor the 'via' can be easily pulled out along with the capacitor lead, and when this happens you have to take an extra step in replacing the cap. To ensure that the top to bottom layer connection is still made properly, you have to insert a small thing piece of wire folded over at the top and bottom, with just a little bit folded over at the top layer, then solder it at the top without filling the hole for the lead, then insert the cap, then solder the lead at the bottom layer. It's a bit of a pain but you have to make that connection again without the benefit of that plated 'via' now.
Sometimes the lead is exposed on the top side too, such as with many resistors. This means you can solder the lead at the top and bottom too and make the connection with the lead itself. But with electrolytic caps this is not usually the case unless they lay down on their side. When they stand up there's usually no way to solder at the top side so a tiny wire has to be used. If the cap is near the edge of the board you might jumper the leads around the edge of the board with some good copper wire with insulation, but that's not the case usually either. The wire cant be too long either or significant resistance might be introduced into the circuit that messes things up.
From the looks of it, that one cap was only damaged by someone who did not repair boards very often and so did not realize they were touching the cap with the iron when they worked on the transistor. The cap is probably ok then.
Just to note, removing a component from a double sided board is a little more complicated than with a single sided board. The double sided board has small 'vias' that run from one layer to the other, usually some sort of plating that forms a little tube that runs from the top layer to the lower layer. That forms a connection between the two layers. This is important because when you insert a large component like a capacitor, you usually can only solder the leads onto the bottom layer. The top layer gets it's connection from the metal plated 'via'. Without the via, the connection to the top layer would be removed and that could cause a break in the circuit and cause the whole thing to malfunction badly.
The problem is, when removing the old capacitor the 'via' can be easily pulled out along with the capacitor lead, and when this happens you have to take an extra step in replacing the cap. To ensure that the top to bottom layer connection is still made properly, you have to insert a small thing piece of wire folded over at the top and bottom, with just a little bit folded over at the top layer, then solder it at the top without filling the hole for the lead, then insert the cap, then solder the lead at the bottom layer. It's a bit of a pain but you have to make that connection again without the benefit of that plated 'via' now.
Sometimes the lead is exposed on the top side too, such as with many resistors. This means you can solder the lead at the top and bottom too and make the connection with the lead itself. But with electrolytic caps this is not usually the case unless they lay down on their side. When they stand up there's usually no way to solder at the top side so a tiny wire has to be used. If the cap is near the edge of the board you might jumper the leads around the edge of the board with some good copper wire with insulation, but that's not the case usually either. The wire cant be too long either or significant resistance might be introduced into the circuit that messes things up.
From the looks of it, that one cap was only damaged by someone who did not repair boards very often and so did not realize they were touching the cap with the iron when they worked on the transistor. The cap is probably ok then.
