20V at dc jack but drops to <1v when plugged into motherboard

[bascotie]

Hi guys,

I'm working on a laptop and trying to figure out if I need to replace the dc jack board, cable, or motherboard. Here's a picture of the setup:

http://imgur.com/I43SMhy

What I've tried:

- Manually shorting start pins to start the computer
- 2 other charges
- I get 20v measurement from the charger
- If I unplug the cable shown in the picture at MOTHERBOARD end, I DO get 20v at the DC JACK.
- As soon as the motherboard side of the cable is plugged in, I start reading .4-.8v at DC JACK.

Before ordering a dc jack, cable, or motherboard, is there a way I can narrow this down to save time on the parts I order?

Thank you!!!

 

[Tha fios agaibh]

Looks to me, there's a short in your mother board. Try and follow the tracers back to the charging section of mb. Perhaps there is a shorted component? Worth a look before shelling out money out for a new mb.

 

[bascotie]

Looks to me, there's a short in your mother board. Try and follow the tracers back to the charging section of mb. Perhaps there is a shorted component? Worth a look before shelling out money out for a new mb.

Thanks for that info. I'm not too good at following traces (I haven't done it before).

I think we have at least determined that it is the motherboard though. If I unplug just the connector from the motherboard side and measure power output at the connector itself, I do get 20v which tells me the cable is not the problem.

 

[bsco]

for what it's worth...with adaptor plugged in, try to feel around the board with your finger for a hot spot......or spray the board with some freeze spray......then hoop up your adapter and watch to see where the frost first disappears......the part that is drawing the most current will melt the frost coating first......at least it will help guide you to the right area before spending money on a new board...could be as simple as a shorted SMD cap....