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176 posts

Master Geek


Topic # 30585 13-Feb-2009 21:57
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Hey Geeks,

My friend asked me to have alook at her Dell Latitude D505 laptop. the problem is that it will not run off AC power.

Here is what happens:

Connect AC charger to mains,
Yellow light on the charger turns yellow,
When i connect the charger to the laptop the yellow light on the charger turns off and the computer will not run... (kind of seems like it shorts out)

I have had alook at the mobo and can not see any signs of damage...
The computer will boot only off the battery, (there is only 6% charge left in the battery.

I was thinking it could be a faulty charging unit. however my friend has tried it with other dell chargers with the dame voltage and amp rating and apparently it did the exact same thing i.e. not boot up off ac power / yellow light goes off when connected to laptop. is it possible that the ac adapter on the laptop is just farked?

Cheers

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18 posts

Geek


  Reply # 196271 17-Feb-2009 13:25
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Have Been Reading Around On This For You And Come Across This,

I hope It helps

But This Is From Someone Who Had A Similar Problem As You Stated

This Is Not From Me Mind This Is From A Person That Stated This!!




Just repaired a laptop with the same symptoms:
Won't charge the battery, won't power from AC.
Also if you power the AC adapter when not connected to laptop you get green power LED on the adapter. When you plug it in the laptop the green power LED immediately goes out.

Opened it up and found SO-8 P-ch mosfet by the DC input socket. Source (pins1,2,3) is connected to the inner barrel (+19.5V), Gate 4 gets driven low, applying the input to the Drain. (pins 5,6,7,8) On my board the drain was short to GND. Applying power directly to the Drain via a current limited bench PSU (set 1A limit) showed a couple of volts.

Placing a finger on the opposite side of the board revealed a SMT ceramic cap getting hot.
CP13 I think. Opposite side to the power connector, almost under it. I would guess at 1206 or slightly larger and there is an 0402 cap just next to its bottom pad at 90 degrees to it. Cap was glued before soldering so had to flow both sides at the same time with a soldering iron and force off. Would likely have been 1uF or bigger 25V. Removal restored operation. Runs OK without but would suggest putting something in there 0.1uF 1206 50V, perhaps a couple stacked ?

BTW you have to strip down everything and remove the main board to get to the cap :-(

Hope this info is of use to someone....

(EDIT) correction: cap is PC13. Pic showing location of failed cap -http://www.die4laser.com/D505fix/









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