Quote:
Originally Posted by glatt
One more question, which may sound kind of dumb after all the information you just provided, but the fan in my 2 year old Dell at home makes a fluctuating noise.
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As UT notes, a power supply may change fan speeds based upon temperature. These design variations are numerous. Early versions has a thermistor inside the fan alongside a transistor and hall effect sensor. Yes, electronics are even inside each fan.
A computer assembler really cannot duplicate this. That power supply fan must move enough air to also keep the case cool in a 100 degree room. IOW that fan control must be integrated with other electronics on motherboard. Dell can integrate that fan control. Same may be too complex for a computer assembler for a clone machine.
Easier is to integrate under motherboard control a fan that often makes creates noise - CPU heatsink fan.
CPU temperatures can vary drastically. To appreciate how much, view why that power supply is located on motherboard adjacent to the CPU. A CPU may go from drawing less than one amp to tens of amps. To make a CPU even hotter, that current demand may occur in microseconds. Therefore a CPU fan may power cycle because CPU power consumption can vary greatly.
Another sidebar - why do fans fail? Many will blame only what they can detect - a sticky or worn bearing, or excessive dust. Fans are designed with sufficient torque to overwhelm such restrictions. However, if fan electronics sensor gets misaligned, then actual fan torque can be signficantly reduced. Some fans may not startup everytime or may eventually start moving later. One such fan over a generation ago resulted in three separate service calls involving a long airplane trip before a mysterious failure was finally traced to a 'sometimes sticky' fan.