The worst case I’ve had was an IBM ThinkPad that had a bowl of cheerios and milk spilled into the keyboard. I’ve also saved a switching power supply and 2m transceiver that were submerged in salt water. I lost an inexpensive MP3 player to the rain, despite valiant attempts to revive it. It is possible to save an MP3 player or cell phone that’s been used in the rain or dunked in a pool by mistake. However, you really want to get at the components and circuit board, and that’s difficult with devices that have no obvious entry points.
The goal is to remove any water and, more importantly, any residue that was carried by the water or caused by water interacting with the electronics. So, if your AM radio took a dip in the sea, you’ve got to get rid of the salt as well as the water. Clean, fresh water is less problematic, but ponds, lakes, and toilets tend to be filled with something other than clean and fresh liquid.
So, my solution for submerge goes like this: First, remove all sources of power, including batteries. This includes the thin lithium cells used in laptops, camcorders, and other handheld devices, and the 9V batteries used as backup for clock radios. Most laptops have at least two batteries. Next, disassemble the unit if you can. Remove speaker cones and anything else that would be damaged by additional contact with water. Next, spray the components and board liberally with distilled water. Use a hand-pump sprayer on the highest setting — you want a powerful stream of water, not a fine mist. If the unit was immersed in salt water and it contains a power transformer, then dunk the part of the board containing the transformer in distilled water. The idea is to dissolve any salt deposits that may be forming between the windings. Follow up with a rubbing alcohol chaser to displace the water. Now, examine the board for deposits between the traces. If you spot any, remove them with Q-tips and either rubbing alcohol or an alcohol-based cleaner. Dry the device with paper towels and place it in front of a fan in a warm (but not hot) room. Don’t use a heat gun or stick the board in your oven.
Physically check the device after four or five days. It should be bone dry. If it isn’t, then put it away and check it in another few days. When you’re satisfied that there’s no water in the device, drop in the batteries and power it up. Hopefully, all will be in working order. If not, well, most warranties don’t cover water damage anyway. At least you’ve learned something from the teardown. If you have any tales of your own water rescue attempts, or you’ve developed a killer process for saving dunked electronics, please consider sharing them with our readers. NV