Charging light wont come on - Dell Inspiron XPS M140 Notebook

A) AC adapter (Charger) is bad.
Use a multimeter, and check it out.

[ DC Voltage.
Test plug of cable that plugs into laptop.
Positive (Red) probe lead of multimeter, to Center Hole of plug on AC adapter.
Negative (Black) probe lead touches outside cylindrical metal shell.
You should read close to 19.5 Volts (DC) ]

AC adapter checks out OK?

B) DC Power Jack is bad

[The DC Power Jack is the port on the laptop, that the AC adapter plugs into. On laptop may be marked DC_IN ]

Damage to DC Power Jack prevents laptop from charging, or running strictly off of the AC adapter.

Battery removed take a No.2 pencil's eraser, and see if you can gently move the Center Pin, of the DC Power Jack.
ANY perceptible movement means replacement of the DC Power Jack.

The pin itself may not move, and the entire jack moves.
The good news is the DC Power Jack is not soldered to the motherboard.
It is soldered to a separate, therefore replaceable, small circuit board,

http://www.parts-people.com/index.php?action=item&id=3698

Click to enlarge. In the photo the DC Power Jack is at the back on the right.
This is is what the DC Power Jack, looks like not installed on that small circuit board,

http://www.elept.com/dc-power-jack-for-dell-inspiron-xps-m140-m1710-m1210-m2010_p2971.html

Looking at the view on the right, note the pins sticking out.
You are looking at the back view, and the jack is laying on it's side.
The pins go through the laptop's motherboard, and are soldered to the motherboard.

Where the pins are soldered to the motherboard is a solder connection. Commonly referred to as a Solder Joint.

Plugging in, and missing the hole of the jack, can cause the AC adapter plug to damage the DC Power Jack, by bumping into it.

Bumping into the plug of the AC adapter, while plugged into the DC Power jack, can cause damage to the jack.

Can cause cracking of the above mentioned solder joints. This leads to an intermittent contact, and eventually no contact, of the DC Power Jack TO the motherboard.

In this case the solder joints are just re-soldered.

Damage to the body of the jack itself means replacement of the DC Power Jack, or replacement of the USB/DC Power Jack circuit board, itself.

(Unless you, or an acquaintance can un-solder, and solder real well, the option may be to just replace the USB/DC Power Jack circuit board)

DC Power Jack proves to be OK?

Problem is one, or more Power MOSFETs on the motherboard.
These determine if the Battery needs a trickle charge, or a full charge, or no charge at all.
Also determines if the laptop is to just run off of the AC adapter, and not the Battery.

This example is for HP Pavilion dv6000 and Pavilion dv9000 series of Notebook PC's. You can use it for cross-reference information.
(Location of the Power MOSFETs on your laptop's motherboard. General idea of what they look like ),

http://mayohardware.blogspot.com/2010/04/important-parts-on-dv6000-and-dv9000.html

What? Looks like motherboard replacement to you?
OK
Let's price a Fairchild Semiconductor International - FDS6679 - Power MOSFET,

http://www.mouser.com/Search/Refine.aspx?Keyword=FDS6679

If you buy one the cost is $1.01 USD

Look to see if the Power MOSFET/s are burned. Blackened, bubbled, or blistered.

There is one more small component, that if bad will produce the same results;
Ceramic Capacitors.

Look back at the Mayohardware blog. Look at the second photo down with the AO4407 Power MOSFET circled in Yellow.

Note the small rectangular shape to the immediate right, that has the wide dark band on it. There is one above it, one above that, and one to the right of the top one.

See if any of these, (No matter what the size. Look at all of them), are burned. Blackened, bubbled, or blistered.

http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT/_/N-b2cj?P=1z0wquyZ1z0t6fg

NOT stating these are ones to use. Just showing average cost.
.42 to .76 cents USD. Approximately a half dollar to three-quarters of a dollar.

Motherboard?

Average example,

http://www.amazon.com/Dell-Inspiron-M140-Motherboard-HC425/dp/B001155N0U

$200 USD

Average example of the -> package type of the Power MOSFETs used,

https://docs.google.com/viewer?a=v&q=cache:oER5NNz8cwcJ:www.fairchildsemi.com/ds/FD/FDS6675BZ.pdf+Fairchild+FDS6675BZ&hl=en&pid=bl&srcid=ADGEEShOhWPjm_M-ROHme4iEMrztCTOd-28jNiy1hVLQQh_VOyv8zcXEVDB_iTQA6MuZO88UmRkDgjyW9j4CP2aIJ-4DS-h6JNM3lvxldeApQeecmz_DADCw1s7tmNLxfPknqX14SZP6&sig=AHIEtbS_rYUAeo_8rB9YHkW05ZjLqeH4Jg

http://www.youtube.com/watch?v=5uiroWBkdFY&feature=fvwrel

You don't need a Soldering Station. A low Wattage soldering iron, and that tip.

http://support.dell.com/support/edocs/systems/xps140M/en/sm/index.htm

Regards,
joecoolvette