A technician installs a replacement processor into a desktop system. Upon pressing the power button, the cooling fans spin briefly for less than one second before the system immediately shuts down. The system will not react to subsequent power button presses until the AC power cord is unplugged and reconnected. When the technician disconnects the dedicated 8-pin +12V CPU power connector from the motherboard, the system fans run continuously upon powering on, though no display output or POST occurs. Which of the following is the most likely cause of this behavior?
- The power supply unit is entering a protective safety shutdown due to a short circuit or over-current condition on the +12V CPU power rail.Cevap
- BThe operating system bootloader files have corrupted, causing the motherboard to abort the system boot sequence before video initialization.
- CThe motherboard requires high-density SO-DIMM memory modules to support the increased thermal design power of the new CPU.
- DThe technician skipped establishing a plan of action and replaced the CPU without verifying overall system power requirements.
Cevap
The power supply unit is entering a protective safety shutdown due to a short circuit or over-current condition on the +12V CPU power rail.
The system exhibiting a momentary fan spin followed by complete power loss—requiring the AC cord to be pulled before it will respond again—is a classic indicator of a power supply tripping its short-circuit or over-current protection logic. Because unplugging the +12V CPU power cable allows the rest of the board to remain powered, the short circuit or severe electrical failure is located on the CPU power circuit.
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Anahtar Kavram
PSU Over-Current / Short-Circuit Protection Latching on +12V CPU Rail