Adding more memory is one of the most common upgrades performed on computers, and portables are no exception. Perhaps the biggest problem with laptop system upgrades is that most have only one or two sockets for additional modules, and often one or both are filled when the system is new. If both are filled, you will have to remove one of the modules when adding another.
For example, many of the higher-
Removing or installing memory in most laptop computers is very simple. Most have an access panel on the bottom of the unit that can be removed with one or two
Figure 6.8. Removing memory access panel.
If your system is different, you should
Figure 6.9. Removing a DIMM.
The installation process is just the
Chapter 7. Power
This chapter covers power for portable systems. Normally laptop or portable systems have options for several sources of power, including AC (alternating current; found in the wall sockets of most
AC (alternating current) is the type of power supplied by wall outlets. AC is so named because it reverses direction at regular intervals, normally 60 times per second (60Hz) in the United States, and 50 times per second (50Hz) in other
When an AC or DC adapter is used, it converts the 120/240V AC or 12V DC to the proper DC input voltage for the system. The problem here is that the actual voltage required can vary from 2V to 24V for different systems (although most are 15V or 16V), and many different types of physical plugs and connectors can be used. Sometimes even the same type of plug can be used on different systems but have the
You have four main issues to consider when plugging an external power adapter into a device:
Voltage output ” All portable systems I know of require DC input from 2V through 24V, with most using either 15V or 16V. If you supply the wrong voltage, it may or may not cause damage to the unit, depending on the design of the internal regulators and battery charging circuits.
Current ” Most devices (such as portable computers) require DC power input; however, some devices use AC current. Plugging in an adapter with AC output into a device requiring DC power (or vice versa) will likely cause damage to the unit.
Tip size and shape ” Obviously the correct size and shape tip is required for the tip to fit into the receptacle and make good contact.
Tip polarity (DC only) ” A power tip will normally have an inner and an outer conductor. The inner conductor may be positive or negative (most use a positive inner conductor). If you get this one wrong, it will most likely do permanent damage to the device.
If you study the small writing on the adapter, it normally
If you mix up or lose adapters, and are unsure of which adapter goes with a specific device, you may need the manual or documentation for the device to determine the power requirements. In some cases the documentation is inadequate. As an example, I was recently trying to use an external FireWire drive that required an external power adapter. The original adapter was lost, and the manual only indicated that the unit required 9V of DC power, but nothing about the tip polarity. I purchased a universal adapter that came with multiple tips and the ability to set different voltages. I determined which tip was required by testing each one, and I set the voltage properly to 9V. However, I didn't know for sure what the tip polarity should be because it was not marked on the unit or in the documentation. Because most devices use a positive inner conductor, I set up the universal adapter that way and plugged it in. After only a few seconds, visible smoke
Although it is usually best to use the original power adapters that come with the computer or other device, several companies make universal replacement AC (wall current) or DC (auto/air) power adapters that feature interchangeable tips and voltage settings (see Figure 7.1). Perhaps the best of these is the ChargeSource adapter created by Comarco and distributed exclusively by Targus.
The ChargeSource adapters incorporate a patented design with interchangeable tips (called PowerTips) that automatically selects the correct voltage and polarity for the intended unit. Interchangeable wall socket plugs allow the unit to operate on any type of wall socket, either in the United States or overseas. A DC (auto/air) version is also available that will plug into any standard 12V automobile or airplane socket (see Figure 7.2).
The ChargeSource power adapters are only a half inch thick and weigh 8.5 ounces (including the cables) and will work with almost any laptop, PDA, or cell phone on the market. They are rated at 70 watts of output power, which is enough for most laptops. Note that there are some laptop models that require up to 120 watts of power, and using more power than the adapter is designed to supply may cause it to overheat. Some versions are sold with specific tips, whereas other less commonly used tips are available separately to cover most of the systems on the market. With the right tip, this type of universal adapter can even power
For more information on the ChargeSource adapters, you can visit these sites:
I recommend having at least one spare power adapter because, as with most power supplies, they take a lot of stress and can