Ok, first of all do you have a 3rd party or a Sony brand of ps1 controller. Yes, it makes a difference, because sony makes their controllers dAMN hard to solder to compared to such controllers as Mad Catz and Pelican/Gamestop *same thing now.* First of all, if you're trying to figure out which point is the ground, look at the green traces that go around the board, there should be one connecting from ground to ground, so essentially looping the entire controllers, and then going into the chip, and if it's the positive side, then it should be going straight into the chip with no side routes. If you're still suck, here's what you can do:
-Plug in your psx controller with the frame all off so you can see the contact points into your playstation/playstation2
-Take a long piece of wire, and strip both ends enough so that you can press each of them onto a suspected solder point, so you can essentially do what the button does and short the connection.
Now for the fun part, I suggest fighting games for this because it's the easiest to see which button is being pressed, and therefore go into Practice/Training mode, load up a character (you might need another controller for this), and set it up so your characters standing still and so is the enemy. Now, if you're having trouble knowing which is the ground and which is the positive, here's the easy but tricky part that will tell you what you need to know:
-Press one end of the wire onto one side of the button you want to test.
-Press the other end of the wire onto the other side of the button you want to test.
If the character punch/kicks you know you gotta button, and you're half way there. If nothing happens, either A: you're not touching it hard enough or slipping, or B: that ain't a contact point.
Now here's the test: while holding one side of the wire to one side of the contact point, place it onto another known contact point's POSITIVE end (not ground.) If that button is activated then you know the wire you're holding is a ground. If nothing happens, then the other wire you were holding earlier is the ground. You can test this by switching your original suspected ground's contact point's wire that you were first holding and keeping the other wire on that known POSITIVE contact point. Do this with all your buttons, and you will soon know which is the ground, and which is the positive side.
-Very primative, but works great, and doesn't cause any harm to the controller. Just don't attach the otherside to like a battery or something.
-Good Luck
-CthulhuLuke