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A 'power supply tester' is a tool used to test the functionality of a computer's power supply. Testers can confirm the presence of the correct voltages at each power supply connector. Testing under load is recommended for the most accurate readings.
The ATX specification defines the Power-Good signal as a +5-volt (V) signal generated in the power supply when it has passed its internal self-tests and the outputs have stabilized. This normally takes between 0.1 and 0.5 seconds after the power supply is switched on.
Power supply may be bad Long continuous beep tone Memory failure Steady, long beeps Power supply bad No beep Power supply bad, system not plugged in, or power not turned on No beep If everything seems to be functioning correctly there may be a problem with the 'beeper' itself. The system will normally beep one short beep. One long, two short beeps
80 Plus (trademarked 80 PLUS) is a voluntary certification program launched in 2004, intended to promote efficient energy use in computer power supply units (PSUs). Certification is acquirable for products that have more than 80% energy efficiency at 20%, 50% and 100% of rated load, and a power factor of 0.9 or greater at 100% load.
#PS_ON pin is marked by number 16. PS-ON Signal is a pin on a 20-pin or 24-pin ATX-specified power connector used to turn a personal computer power supply unit on/off. The PS_ON pin is normally pulled high in an open-circuit, but will turn on the power supply when it is pulled low, by shorting it to the common signal (COM).
Some motherboards have a built-in display to diagnose hardware problems. Most also report POST errors with audible beeps, if a PC speaker is attached. Such motherboards make POST cards less necessary. When these diagnostic cards were first introduced motherboards were expensive and well worth troubleshooting and repairing.
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A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of a power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage output (V o ), like dropping a crowbar across the output terminals of the power supply.