Trying to solder my PS1 pcb

I have a Dual shock 1 PSB i am trying to solder but its been soldered before but i cut the wires off to move the pcb to a diff stick and am using the wires already in the stick connected to the buttons and the joystick inside.

My problem right now is when i solder it how do i know if it will work?

Also there is still very small pieces that i can’t cut of older wire/solder so what do I do about that do I resolder the wire onto the broken pieces and will it work? Or do I pick a diff spot on the pcb?

The best thing to do is remove the old wires completely. Heat up the old solder and remove it using a desoldering braid. The old wire fragments will then either come up with the solder or be easily removed.

As for knowing whether the connection will work or not… it’s this simple: if you soldered properly, it will work; if you didn’t, it will not.

If you don’t know how to solder properly, read the soldering guides in the sticky and at slagcoin.