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These can manifest only at specific environmental conditions, high clock speeds, low power supply voltages, and sometimes specific circuit signal states; significant variations can occur on a single die. [9] Overstress-induced damage like ohmic shunts or a reduced transistor output current can increase such delays, leading to erratic behavior.
For example, a 900-watt power supply with the 80 Plus Silver efficiency rating (which means that such a power supply is designed to be at least 85% efficient for loads above 180 W) may only be 73% efficient when the load is lower than 100 W, which is a typical idle power for a desktop computer. Thus, for a 100 W load, losses for this supply ...
A power-on self-test (POST) is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on. [ 1 ] POST processes may set the initial state of the device from firmware and detect if any hardware components are non-functional.
A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a duration longer than one second may induce ventricular fibrillation at currents as low as 30 milliamperes (mA). [12] [13] With direct current (DC), 90 to 130 mA are required at the same duration. [14]
Troubleshooting is a form of problem solving, often applied to repair failed products or processes on a machine or a system. It is a logical, systematic search for the source of a problem in order to solve it, and make the product or process operational again. Troubleshooting is needed to identify the symptoms.
The product was analyzed or tested to confirm the failure, but “a failure or fault” could be not found. A common example of the NFF phenomenon occurs when your computer “hangs up”. Clearly, a “failure” has occurred. However, if the computer is rebooted, it often works again. The impact of NFF and intermittent failures can be profound.
For example, for a domestic UK 230 V, 60 A TN-S or USA 120 V/240 V supply, fault currents may be a few thousand amperes. Large low-voltage networks with multiple sources may have fault levels of 300,000 amperes. A high-resistance-grounded system may restrict line to ground fault current to only 5 amperes.
The ATX specification requires that the power-good signal ("PWR_OK") go high no sooner than 100 ms after the power rails have stabilized, and remain high for 16 ms after loss of AC power, and fall (to less than 0.4 V) at least 1 ms before the power rails fall out of specification (to 95% of their nominal value).