PC Repair and Maintenance: A Practical Guide (Charles River Media Networking/Security)
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The most obvious sign of a damaged motherboard is a burnt or otherwise visibly damaged part. Naturally, motherboards can die without any visual signs. If you are sure the power supply works and is turned on, set for the correct voltage, and is connected correctly, and the CPU is good, but you attempt to boot and absolutely nothing happens, it is likely that the motherboard is dead. In this situation, a POST card such as Micro 2000's Micro-Scope (see Chapter 11, Troubleshooting") might not show anything. The only answer here is to try to replace the board with one that is compatible with the case, CPU, power supply, memory, and peripherals. If this is not feasible, a new computer can often be built with at least some of the existing parts.
Motherboard Batteries
Motherboards come with batteries, usually replaceable lithium coin cells. These batteries are in place primarily to keep the time/date clock running and maintain BIOS setup program settings. The batteries usually last at least six years. If a computer loses its BIOS settings and time/date memory every time it is shut down, you'll need to replace the battery, if possible. The POST (see Chapter 2) might show an error message if the battery has died. Moreover, if someone has set a supervisor password in the setup program, and now has forgotten it, and the computer cannot boot, the only way to reset or cancel the password is to remove and replace the battery. You might be able to use a battery tester to test the voltage of the battery without removing it. Make sure the polarity of the probes matches the polarity of the battery, and check to see if the battery is still good. Double-check the motherboard documentation to make sure the battery is the right type.
Battery Replacement
If the BIOS settings are still valid and you need to replace the battery, know that the motherboard might have a capacitor that will hold a charge just long enough for you to replace the battery without losing your settings. However, whether or not it has such a capacitor, it is recommended to write down all non-default BIOS settings before changing the battery. Changing a replaceable battery is a simple but delicate operation. Carefully remove the old battery and insert the new one, as shown in Figure 3.15. Just make sure that the new one is of the correct type and that it outputs the correct voltage.
| Note | There is a long thin tab on some battery holders that at first glance looks as though it should be pulled up to remove the lithium coin cell. It is really just a spring tab, and if pulled up will permanently lose its ability to hold the battery down and make contact, thus almost always ruining the board. In this case, slide the battery to the open side and remove it, as shown in Figure 3.15. |
Some motherboards have batteries soldered in place. Many of these boards have terminals for connection of a replacement battery; in these cases, the dead battery is left in place, as shown in Figure 3.16.
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