Section 1: Power System
Background:
This section is designed to assist the troubleshooting of a computer system that has no signs of life. Some of the techniques discussed are limited in scope to the diagnosis of a "dead" computer system, while other tips can and should be applied to all diagnostics. If the issue that you are troubleshooting is intermittent, begin the diagnostic process by verifying the Power System; many intermittent problems have roots in faulty electronics.
General Inspection:
Before you begin any troubleshooting process, you should perform a general inspection of the system in question. This inspection requires a little bit of knowledge as to what to look for. This guide will cover the major items.
- Leaky/Crusty capacitors - Capacitors are those little round cylinders with the metal tops. When they are working properly, they help to regulate power fluctuations and perform various other sundry duties with the electrical current. Capacitors are vulnerable to power surges and other abnormal current conditions. Some motherboard manufacturers utilized a bad electrolytic formula in the creation of their capacitors, causing them to burst without an abnormal current condition. Therefore, the presence of blown capacitors does not always imply that the machine was hit by a power surge. Search all over the board for capacitors that are crusty on top, or look like they are about to pop (the tops should be flat not bulged). If your motherboard has one of more capacitors that meet this description, you are probably going to have to purchase a new motherboard. You might be able to take your motherboard to a local repair shop and have them solder new capacitors to the board, but that would not be cheap, and it does not guarantee that the other capacitors will not just blow as soon as you power it up again.
- Malfunctioning wire coils - You should inspect the entire motherboard for coils that appear to be scorched or melted in any way. Coils are those cylindrical wraps of wire that are either freestanding or wrapped around an iron core. If you have coils that appear burnt, or have wires with melted insulation, your motherboard has a severe electrical problem and you should replace it.
- Scorch / Burn marks - If during your inspection of the motherboard you see scorch marks or a place where the PCB appears to have been burnt, it is quite likely that a component of the motherboard has failed and has caused damage to the PCB. Your best bet is to replace the motherboard.
If you locate any of the above during your inspection, you should take your computer to a professional technician.
Power Supply
Power supply. The power supply is the device that converts line current (Alternating Current) into the current that your computer needs to operate. There have been a lot of different "form factors" or layouts for the internal components of a computer. The three major design classes in use today are AT, ATX, and BTX. You need to identify which design the internals of your case are. This is important because the voltage layout of your power supply will vary depending on the form factor. I will not consider AT power supplies in this discussion because they appear so rarely. If you need help determining what form factor your case and motherboard conform to, you should look on the OEM label for your power supply. The form factor is nearly always printed there.
If you have access to a multi-meter, you can utilize the links in the resources section to ensure that the power supply is putting out the correct amount of voltage. Without load on the circuit, the power supply should be putting out approximately the right voltage (a 2% variance is okay). You will have to short certain pins on the connector in order for the power supply to turn on. For an ATX power supply, you need to short pin 14 to ground. (The action of shorting pin 14 to a ground is commonly known as the "paperclip test")
If the power supply does not turn on, or is putting out incorrect voltage, you should replace it. If you do not feel comfortable performing the installation yourself, take the computer to a local repair shop. The fee to install a power supply should not be more than about $40 plus the price of the part. When selecting a new power supply, you should replace it with one that is rated for at least as many watts as the previous supply.
If you do not have access to a multimeter or a power supply tester, you can always bring your power supply to a local repair shop. A good shop would not charge you much to test your power supply for you. Power supplies are also typically fairly inexpensive, you could always try just replacing it (purchase your supply from a store with a good return policy) if you live far enough away that you do not want to have to make so many trips.
Resources
Pin-outs and Voltages for common form factors:
Proceed to next section: 2. POST