Capacitor Change on Mac Motherboards
Before going for a capacitor replacement (Warning: High Voltage), have a look at the board and try to find any signs of capacitor leakage (it will look like Cola spilled on the board). If there is any, clean it off with some alcohol and cotton buds/Q tips or alternatively remove the battery and SIMMs and stick the motherboard in the dishwasher. Seriously! If you're not keen on the dishwasher then it could also be cleaned using water in a bowl. If going for any cleaning involving water, ensure that the board is fully dry before trying it out. In my experience this often cures the Simasimac problem, for how long is anyone's guess.
Most electronics repair shops should be able to replace the capacitors if you can't yourself.
The Mac´s checkerboard aka Simasimac problem is common on the SEs and Classics. The solution is usually to re-seat and or clean the ROM connections, not the RAM. The M0001s had similar vertical stripes related to ROMs as well.
Washing the logicboard likely resulted in a similar effort and/or water trapped in the sockets is actually enhancing the connection. Once the board thoroughly dries, you may once again get the pattern. Either way, you are luck your impetuousness didn't short out the whole board.
Which Capacitors do I need for my Macintosh Motherboard ?
A voltage value is the maximum voltage the capacitor can take. If replacement capacitors have a higher rating, they should work. Generally speaking using higher voltage caps in PSU's i've heard is a good idea for longeveity, then again im not sure of the long term effects if another ocmponent goes bad, maybe it can over supply voltage to something else.
Macintosh Classic requires following capacitors on the motherboard:
seven 47 µF/16V capacitors,
one 1 µF/50V capacitor
The Classic II requires
three 47 µF/16V capacitors,
eight 10 µF/16V capacitors,
two 1 µF/50V capacitors
ten of the 47 µF/16V capacitors,
one of the 1 µF/50V capacitor
The easiest way to remove the old caps is to use two soldering pencils at one time. That way you do not put mechanical stress on the circuit board (as you do when you heat one side at a time). A grounded 15 watt soldering pencil is available from Radio Shack for under $10. So, if you already have one soldering pencil, go pick up a second one and make this job easy for yourself.
If you try to use just one pencil, by the time you can heat the second pad, the first will have cooled. With the one-pencil-method you are forced to either get the entire cap and board so hot that the solder will stay melted while you move the pencil from side to side, or you end up bending the cold solder on one side, while lifting the other side. That over-heating and/or bending is what typically leads to lifted pads on the circuit board.
With the two pencil method, you just apply a pencil to each end of the cap to be removed and wait until you can gently lift the cap with little to no resistance. It's useful to have a damp sponge on hand, as sometimes the cap sticks to one pencil tip or the other and it can be wiped off on the sponge.