Odd Pulsing Of Power In Liquid Damaged Mobo

kjtruitt0

Honorable
Sep 23, 2013
10
0
10,510
D630 suffered chocolate milk spill I'm told. Bought it on ebay. Cleaned up the board with a toothbrush and isopropyl (70%--didn't have 99%). Most of the accumulation was on the underside of the mobo near the dc jack and up to the first set of usb ports about 3 inches away.

Still, no power. With black multimeter prong on the casing of the dc jack and red prong on one of the steel plates on the back of the jack (that is soldered into the board), I got nothing but a strange little pulse at about one second intervals during which the meter indicator would bump up a few volts.

I got this also on a few components on the board very near the dc jack--rest of the board is dead.

On functional boards I get 19.5 volts with the multimeter prongs in the same position as described. So I thought perhaps the dc jack had some kind of internal fracture that was keeping the power from getting to the board. This would be an odd coincidence since it would have had nothing to do with the liquid damage. So I actually pulled a functional dc jack from another d630 and put it in. Same thing--the same pulse. This time, I noticed that the power indicator light on the ac adapter was showing the same pulse.

Anybody know what the deal is? Especially with this pulse? To summarize:

-cleaned liquid damaged area
-still no power at read end of dc jack where there should be 19.5 volts--just this pulsing of a few volts at 1 second intervals

It also appears that if you take even a good dc jack out of the board and plug power into it, you don't get power at the back. So you only get that by virtue of the circuitry on the motherboard bringing the power back at some point. And obviously this is not happening--just that pulse is making it back.

And again, the pulse is only found very close to the dc jack-everywhere else is completely dead.

I am just mainly curious. Any ideas?
 
Solution
Dell power adapters will shut down if they think there is a short in the laptop they are connected to, and will reset after a few seconds. That's probably the cause of the pulse your multimeter is reading.

Casey

cklaubur

Distinguished
Dell power adapters will shut down if they think there is a short in the laptop they are connected to, and will reset after a few seconds. That's probably the cause of the pulse your multimeter is reading.

Casey
 
Solution