Computer Hardware Essentials: Systems, Components, and Power Supply Diagnostics

Introduction to Programmable Systems

Three major trends can be defined in programmable digital systems:

• Large Computers or Mainframes: These systems are designed for massive data processing in the shortest possible time. They come with a very high cost and are primarily engaged in research applications and management.
• Personal Computers and Workstations: Their main purpose is to increase individual productivity.
• Industrial Control and Automation: Utilized in electronic systems to achieve large-scale automation within our society.

The market trend for micro-P circuits is towards increasingly faster, more powerful, and more capable calculation, which in turn drives smaller sizes. These systems also feature minor input/output systems that can interact with the outside world.

External Structure of Microcomputer Equipment

The central unit houses storage units for information, graphics cards, sound cards, and micro-memory. External elements and the central unit are connected by wires with connectors at their ends. These common connectors include:

• DB-15HD (High Density) Female: A 15-pin connector for video output.
• PS/2 Female: Connector for keyboards and mice, also known as mini-DIN.
• USB (Universal Serial Bus): A versatile serial bus connector.
• RJ-11: A modem connector used to connect to a telephone and telephone line (for internal modems).

Computer Housing: External Structure

Computer housings are typically found in three versions:

• Horizontal or vertical desktop tower.
• "Barebone": Compact and very quiet systems.
• Laptops.

Common elements found on the front panel include: LED indicators for disk read/write activity, the power button, and the reset button.

The Power Supply Unit (PSU)

The power supply unit (PSU) is responsible for providing the necessary voltage and current to the computer. It receives 220V and 50Hz from the electrical network and transforms it into DC voltages such as +5V, -5V, +12V, -12V (and +3.3V on ATX models).

Common issues can arise with the power supply. Tools to detect and correct these flaws include:

• Phillips PH2 screwdriver
• Fine-point pliers or tweezers
• Multimeter
• Soldering iron
• Fuses and spare cables

Troubleshooting: System Completely Stopped

1. Check the line voltage. Observe if any lights turn on, if the fan works, or if the monitor activates (if connected to the same outlet).
2. Verify that the power cable is properly connected.
3. Examine the continuity of the power cable (e.g., by trying another cable).
4. Check if the power switch is functional by measuring the resistance between its terminals. Resistance should be high when disconnected and drop when connected.
5. Using a multimeter, verify the output voltage and the "Power Good" signal on the P8 motherboard connector.
6. Check the fuse located inside the power supply unit.
7. Remove all expansion cards and disconnect power from disk drives. Recheck the output voltages and the "Power Good" signal from the power supply. If the power supply is overloaded, replace it if there is still no current.
8. If there is power, calculate the system's power requirements and check if the power supply is sufficiently powerful. Systematically disconnect expansion cards and peripherals until the component consuming excessive power is identified.

Troubleshooting: System Works, Then Stops

Refer to steps g) and h) from the previous section.

Troubleshooting: System Fails After Extended Use

1. Check the power cable.
2. Check if the fan is working and measure the incoming voltages.
3. Calculate the system's power requirements to determine if the power supply is sufficiently powerful.
4. Use a multimeter to check the output voltages and replace the power supply if the values are near the specified limits.

Troubleshooting: Computer Powers On, Black Screen, No Fan/HDD Activity

To start an ATX power supply without a motherboard, connect pins 14 and ground. If the cooling fan does not work, the power supply may be faulty.