A machine that will not power on is not a dead machine. In most cases, it is the cheapest part that has given out.
The power supply is the component that wears fastest, because it works constantly and absorbs every variation in the mains. It is also the one suspected last - even though it explains a large share of the faults that make people think a computer is gone for good.
The power supply unit converts mains current to feed every component. As it ages it does not fail all at once: it gradually loses its ability to absorb peaks in consumption.
The symptoms are easy to recognize:
Replacing a power supply unit is a simple job and inexpensive against the value of a tower. The point to check is the rating: a supply underrated for the graphics card fitted produces exactly these symptoms without being faulty itself.
Three separate parts can be at fault, and the checks run from cheapest to most expensive.
The charger. It is the link that breaks most often, and almost always at the cable - where it enters the brick or just before the plug. The break is internal, under the sheath, with no visible mark. The light on the mains brick, where there is one, already tells you something.
The machine's charging connector. If charging only works with the cable in a certain position, or stops at the slightest movement, this is it. That socket is soldered to the motherboard or linked by a ribbon cable, and it suffers with every plug-in. It can be resoldered or replaced: a routine workshop repair.
The battery or the charging circuit. If the machine runs perfectly on mains power but shuts down as soon as you unplug it, the battery is no longer charging. See laptop repair.
An electrical reset. Switch off, unplug the charger, remove the battery if it comes out, then hold the power button down for around twenty seconds. That full discharge of the circuits unblocks a surprising number of situations, and carries no risk whatsoever.
Testing the socket. Plug straight into the wall, with no power strip or extension lead, and check the socket with another appliance. On a tower, also check the switch at the back of the unit, often flipped by accident while moving the machine.
A cheap charger with interchangeable tips rarely delivers the exact voltage the machine expects. At best it will not charge properly; at worst it does lasting damage to the motherboard's power circuit, and the repair then bears no relation to the money saved.
On a machine you intend to keep, the charger is a bad place to economize. We supply models matched to your exact reference.
A machine that will not power on can also come from the motherboard, the memory, or a faulty power button. That is why diagnosis is done by elimination with a reference power supply: the possibilities are ruled out one by one, rather than replacing parts on a hunch.
On a laptop, a machine that reacts to nothing after a spill calls for specific and urgent handling: see a spill on a computer.
A power supply fault never touches the disk. Your files are intact, and recoverable straight away by connecting the disk to another machine - even if the repair turns out not to be worthwhile. We always check this at the diagnosis stage, before anything else.
Power supplies age faster in some installations than in others. An overloaded power strip, an old circuit, a supply subject to micro-cuts: all of these wear the unit out prematurely and, in time, the motherboard too.
Two inexpensive precautions are worth taking. A power strip with surge protection, which absorbs the spikes caused by lightning or by nearby appliances. And, for a work machine or a server, a UPS, which gives you time for a clean shutdown during an outage - an abrupt power cut mid-write to the disk is one of the classic causes of a damaged system.
Replacing a power supply unit on a tower is readily done at your place. Replacing a charging connector on a laptop requires stripping the machine down and is handled in the workshop.
It is the most frequent cause, but not the only one: the motherboard, the memory or the power button can produce the same symptom. Diagnosis by elimination settles it in a few minutes.
Yes if the voltage is identical and the wattage at least equivalent. A different voltage can damage the machine, and insufficient wattage will never charge the battery.
Yes, it is a routine workshop repair: the socket is resoldered or replaced. On a machine that is otherwise in good condition, it is well worth it.
It can on cheap models with no protection. That is one of the reasons we do not fit bargain power supplies in the machines we repair.
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