The Achilles Heel of a Laptop

September 16, 2011 at 3:33 am (DR1 Charger Board, inspiron 1545, power jack)

The jack to which the power cable is connected on a laptop computer has long been a weak point.  This jack is easily broken by accidentally torquing or pushing too hard on the power cable plug.  If you have small children, it is really only a matter of time before this happens to your laptop.  You can see what happened to one of my Inspiron 1545 laptops in the photo below.

The Power Jack is a Single Point of Failure

When the power jack is damaged, the battery can’t be recharged and you can’t power the laptop by plugging it into a wall outlet.  In a moment, your laptop becomes essentially useless.  You can take it to a repair shop and pay big bucks to have it fixed, or if you are a brave and patient soul with a bit of electronics technician in your blood, then you can repair it yourself.

So where is the power jack located inside the laptop case, and how difficult is it to access and replace the jack?

Well, in years gone by, laptop manufacturers often mounted the power jack directly on the motherboard.  This meant that any attempted repair either involved replacing the entire expensive motherboard or nervously soldering a new jack on to the most expensive board in the laptop (while praying you didn’t damage any adjacent components).

For the Dell Inspiron 1545, there is both good news and bad news in regard to the power jack location.  First, the good news:  The engineers who designed the 1545 had the good sense not to mount the power jack directly on the motherboard.  Instead they put the jack on a smaller board called the “DR1 Charger Board”.  You can see a photo of this little board below.

The DR1 Charger Board for the Dell Inspiron 1545

The power jack is located at one end of the DR1 charger board (see yellow circle in the above photo).  The power jack is not the only connector on the board.  The other connectors are a pair of USB ports, the external VGA video connector, and the ethernet port.  All of these connectors are found on the left side of the Inspiron 1545 laptop.

If you want to repair a broken power jack on your 1545, all you have to do is replace the DR1 charger board (which costs about $100), or if you have the appropriate soldering skills and tools, you can replace just the power jack (which costs about $30).

So, what is the bad news?

The bad news is that the DR1 charger board is the very first board to be installed in the laptop when the laptop is being built in the factory.  Changing the charger board is like changing the timing belt in your automobile.  The timing belt is relatively inexpensive, but the labor involved in taking apart the engine to get to the timing belt is significant.  The same is true for the DR1 board.  Because it is the first thing installed in the laptop, it is covered and hidden by a number of other boards and components.  First in, last out.  A photo of the base portion of the 1545 chassis with all of the boards removed is shown below.   The area where the DR1 board is mounted is highlighted in yellow.

Dell Inspiron 1545 Chassis (all boards removed)

You have to be mentally prepared for 30 to 60 minutes of careful laptop disassembly to get to the location of the DR1 charger board.  And all along the way, you have to keep all the other parts (and the screws used to mount these parts) sorted and stored away safely.  Once you have removed all of these other parts, you will reveal the DR1 board lurking in the upper left corner of the chassis (held in place by two screws circled in yellow in the photo below).

Properly Mounted DR1 Charger Board

As of the date of this blog post, the “official” instructions for taking apart a Dell Insprion 1545 laptop in order to get to the DR1 charger board can be found at the following link:

http://support.dell.com/support/edocs/systems/ins1545/en/sm/chargerb.htm

Have fun!  I’ll have more to say about the joys of replacing the DR1 charger board in future posts.

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Power to the Pooter

September 11, 2011 at 3:58 am (inspiron 1545, power cable) ()

It’s all about the electrons.  They magically come out of the wall, flow through the power adapter and into the laptop and ultimately keep the battery charged and the microprocessor happy.  Nobody gives much thought to the power adapter until it quits working and a new adapter must be purchased.

A frequently asked question about the power adapter is whether to use the 65 Watt or the 90 Watt variety.  As with most things that come from Texas, a Dell laptop wants to go with whatever is bigger.  Use a 90 Watt power adapter.  While a lot of Dell laptops will work with a 65 Watt adapter, they often slow down the processor when they sense that they have been connected to a wimpy power supply.

Another area of confusion has to do with the fact that there are three conductors at the end of the power adapter cable (the end which plugs into the laptop) even though it appears there are only two conductors.  The three conductors are marked in the photograph below.

Typical Dell Power Adapter Connector

Typical Dell Power Adapter Connector

The outer metallic surface is essentially the DC common.  This shielding surface is the “DC zero volt” reference point, and when the cable is plugged into the laptop, all of the internal metal shielding components (i.e., the chassis ground) and all of the circuit board ground planes are connected to this DC common.

The inner metallic surface, which one might easily assume is just the inside part of the DC common, is actually a second, separate conductor.  The inner metallic surface provides the main supply voltage.  The inner surface is nominally 19 volts positive of the DC common when the power adapter is plugged into a wall outlet.

So why is there also a center pin?  This center pin is used for communication between the external power adapter and the motherboard inside the laptop.  So what kind of communication is going on here?  In general, this communication signal lets the laptop know that external power is available and that it is time to start charing the battery.

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To All the Dells I’ve Loved Before

September 11, 2011 at 2:47 am (inspiron 1545)

So this is where I’m going to tell the world about my wonderful experiences maintaining multiple Dell Inspiron 1545 laptops.

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