Dell Inspiron 5150 Power Issues
eBay seems to offer an opportunity to buy a powerful laptop at low cost. The Dell Inspiron 5150 is a good example. When this laptop functions properly, it is a well featured strong performer. Unfortunately, many of the units offered on eBay have issues. I have purchased a number of these units to better understand the nature of these issues. I wrote a companion article that addresses repairing random Dell Inspiron 5150 shutdown problems. This article discusses power issues.
A laptop requires several voltages which are derived from the single voltage provided by the A/C adapter or by the battery. The Dell Inspiron 5150 is able to identify the specific A/C adapter in use via a three contact plug. The plug connector on the laptop is a precision part. The barrel on the A/C adapter plug goes deeply into the laptop connector. I bought a unit on eBay where someone had tripped on the A/C wire to the laptop and fractured the plactic center portion of the laptop connector. I could actually pull the center section out with my fingers. Left in the connector were several narrow contacts very close to each other. When I carefully examined the connector, I realized the central plastic portion of the connector is best served by handling the laptop in a way to minimize stress on the power connector of the laptop. The following photograph is from the rear of the plug. You can see daylight between the inner plastic core and the outer barrel of the plug. If you rotate it, there is lots of light except where the connectors block the view. That center core is attached only at the very rear where leverage is greatest.
There are many internet postings discussing loose power connectors and the ability, for a time, to get the laptop working by carefully positioning or stressing the connection. Some postings refer to heat issues and the resulting need to resolder the power connector. A new replacement connector is also available on eBay. There seems to be an active eBay market for people dealing in Dell Inspiron 5150's with power issues. My experience also includes an eBay ad that alludes to a bad connection as a possible cause of the inability of the computer to recognized the A/C adapter and to charge the battery.
A partially failed A/C adapter may not be properly recognized by the laptop even with 19.42 v DC at the plug. A defective or poorly attached laptop connector will also exhibit the same symptom. A failed or failing power section circuit on the motherboard will exhibit the same symptom. Failing circuitry is especially frustrating because the circuit may work for a few minutes until it overheats. If the cooling fins at the rear of the laptop are partially blocked, the unit briefly running at full speed on A/C will overheat and protectively shutdown. Sometimes you receive a message about overheating, sometimes you don't.
I have not analyzed the power circuit on the laptop to determine the extent to which it protects itself with simple to replace devices such as fuses or more complex protective devices for high voltage, high power, or reversed polarity. Such devices add expense, and I wouldn't expect extensive use of power circuit protective devices. With experience and equipment, it is not difficult to identify and replace defective transistors and diodes. For the typical laptop buyer, this is well beyond the scope of their skill set.
It is easy to apply simplistic techniques and to pay the price. I recently purchased a non-working Inspiron 5150 that failed to recognize the A/C adapter or the battery. To identify the problem, I hooked a known good A/C adapter to the defective computer. No change. Then I made the huge error of hooking up the A/C adapter received with the defective unit to a known good Inspiron 5150. I was rewarded with smoke and an inoperative laptop.
Had I checked voltages at the A/C adapter connector using a spare laptop A/C connector, I would have learned the positive line was shorted to the data line. Once inside both, now defective, laptops, the same data line chip had flamed. This was a very expensive lesson, i.e., always check adapter voltages first. A defective A/C adapter is relatively cheap to replace.
If you would like to participate in the eBay marketplace for Dell Inspiron 5150's with power issues, I hope this article has opened your eyes. You could have a worn power connector on either side of the connection, defective diode, bad trace, fried surface mount device, etc. Based on pricing, it appears folks believe a little dab of solder in the proper place will get things "good as new."
If you require a replacement motherboard for $300 at auction and sell your defective one for $50 at auction, your repair cost can top out about $250 to $300. That suggests in today's market a fair price for a defective machine is $150 to $200 because working machines can go for $400 and up and the used market for screens remains strong. More powerful newer offerings constantly drive down the value of earlier laptops. A current offering is the Vostro 1500 equipped with a Core 2 Duo CPU selling for around $700 new with large hard drive, DVD burner, built in web cam, 4 GB RAM capacity, and the ability to run a 64 bit operating system.
For end users, not people that buy then sell items on eBay, there was a law suit settlement that extended warranties through September 2007 for certain issues.
Remember this article documents my experience and frustrations. I take no responsibility for the ill advised activities of others.