Is there a Dell Power Supply Gremlin?

I’ve seen 2 fairly new Dell laptops recently (a Latitude D520 and an Inspiron E1705) with the same symptoms. With a known good adapter attached to the unit, they do not charge at all, but they run off the battery until the battery dies. I disassembled both and checked the connection between the power jack and the mobo and found them to be solid. I connected a power source directly to the + solder point on the mobo and a ground and found they did not power up at all. If this were a desktop, I would change the power supply immediately, but being a laptop, I’m not sure what (if anything) can be done to fix the problem. Any ideas or suggestions would be very much appreciated.

What I've done:
1. Both units work normally with charged batteries, so I know I'm working with good laptops.
2. Removed, cleaned contacts and re-inserted RAM.
3. Cleaned accumulation from the internal lint trap, i.e., from the CPU cooling fins.
4. Removed, cleaned, re-applied thermal paste and reseated CPU's.

Now what??

 

Some of the power circuitry on the PSU side is probably dead. Can't think of any options after you've tested most of the common problems. Given that the above is true, the only thing you can do is replace the board, unless you can somehow track down the individual components that're busted/burnt and replace those individually.

 

That's what I was afraid of. It's too bad laptop power supplies aren't modular, like desktop units. For a few bad chips, the whole mobo has to go. Does anyone know if the dust accumulation (and possible overheating) is the cause?

 

Dust and/or heat buildup may have caused the fault(s) in the first place, but once the damage is done, it's very unlikely that any amount of cleaning is going to fix it.

 

Some people also mention power surges cause these types of problems. It might be true. I also hate how everything in the laptop is on one board and that whole thing has to go if something went wrong.