Dead. You hit the power button and get nothing, or the fans spin up and the screen stays stubbornly black.
Those two situations feel identical from the chair. They are not the same fault. A computer that will not turn on is either not getting power or not showing you what it is doing, and separating those two is the whole job.
I have had hundreds of these on the bench. The number that genuinely needed a new motherboard is small. Far more came back to life from a different outlet, a stick of RAM pushed back into its slot, or a thirty second power drain that costs nothing but patience.
So we go in order. Cheapest and safest checks first, hardware last. That order is what keeps two hundred dollars in your pocket.
If your computer does turn on but crawls once it is running, that is a different problem. Start with how to fix a slow computer instead.
No power vs no display: the first split
Which of these are you actually looking at? Press the button and pay attention for five full seconds.
- No power looks like nothing. No lights on the lid or the front panel, no fan noise, no faint whir from inside, no keyboard backlight. The machine is a brick and it is silent.
- No display looks alive but blind. Fans spin, a power light glows, the keyboard may light up, you might hear the drive or a chime, and the screen stays black anyway.
No power at all points to the charger, the battery, or the board. A laptop that powers on but shows nothing has a different lineup of suspects: a display fault, a loose cable, or bad memory. Two forks, two paths. Pick yours and follow it down.
One caution before you commit. A screen that is very dim rather than truly black will fool you into thinking the machine is dead. Shine a phone flashlight at the display at a low angle. If you can just make out the desktop under there, the backlight is the problem, not the whole computer, and you are on the display branch after all.
Test the charger with a known-good one
This is where most dead laptops actually get fixed.
On a laptop, the charger is the single most common reason for no power, so it goes first. Look at the brick. Most adapters have a small LED that glows when they have power. If it is dark, try another outlet, then a different cable if yours is the two piece kind that separates in the middle.
Now check the connector. On a barrel plug, wiggle it gently at the laptop while you watch for a charge light. On USB-C, try both ends of the cable and a second port. Charging ports loosen with age and solder joints crack, and an adapter that reads fine on a meter can still collapse under load.
The real test is a known-good charger. Borrow one you know works, and match it properly. USB-C charging depends on wattage: a 30 watt phone charger will not wake a 90 watt laptop, and it may give no sign of life at all, which sends you chasing a fault that is not there. Match the connector and the wattage, or the test tells you nothing.
A word on safety. Skip the ten dollar no-name bricks. A cheap charger that lies about its output can cook a battery, and I have replaced boards that a bargain adapter killed on its way out.
Desktop instead of laptop? The charger equivalent is the power supply and the wall. Confirm the outlet with a lamp, check the switch on the back of the power supply reads 1 and not 0, and reseat the power cable at both ends. No lights and no fan twitch at all points straight at the power supply.
The power drain that fixes a hung machine
A customer once drove forty minutes with a laptop he swore was completely dead. I unplugged it, pulled the battery, held the power button. It booted on the first try. He was not thrilled about the gas money.
Holding the power button with everything disconnected discharges the residual power in the capacitors, sometimes called flea power. It also resets the embedded controller that manages startup, and a hung controller is a shockingly common reason a machine ignores the button entirely.
- Unplug the charger.
- If the battery is removable, take it out.
- Press and hold the power button for a full 30 seconds. Count it out, do not rush.
- Put the battery back, plug the charger in, and try to power on.
Sealed battery, which covers most modern laptops? Same routine, minus the battery step. Some models hide a tiny reset pinhole on the underside, and a straightened paperclip held there for a few seconds does the same job. Check your model’s manual before you go poking blindly.
Reseat the RAM to fix a no-display boot
If your machine powers on but the screen stays black, and the charger and the drain did nothing, suspect the memory.
RAM works its way loose. Heat cycles, one hard bump, a laptop that lives in a backpack, and a stick lifts a fraction of a millimetre out of its slot. That is enough to stop the machine from posting, and reseating the RAM fixes a no-display boot more often than any single trick I know.
Power off completely and unplug first, then run the power drain from the last section while you are in there. Touch a bare metal part of the case to ground yourself before you handle anything. Static you cannot feel is enough to kill a memory stick, and it is the step people skip right before they regret it.
- Desktop: open the side panel, find the long DIMM slots beside the CPU, push the clips at both ends outward, lift the stick straight up, then press it back down until both clips snap closed.
- Laptop: this means removing a bottom panel or a small memory door. The sticks are shorter SO-DIMMs held by two side clips. Spread the clips, the stick pops up at an angle, slide it out, line up the notch, and press down until it clicks flat.
Got two sticks? Test one at a time. Boot with stick A in the first slot, then stick B, then swap the slots. A machine that runs on one stick but not the other just told you which part is bad, and that is a ten minute diagnosis a shop would bill an hour for.
Still black after all that, but the fans and lights are clearly on? Plug in an external monitor. If it shows a clean picture, your fault is the laptop panel or its cable, not the guts of the machine. That is a display repair, walked through in how to fix lines on a laptop screen.
A dead CMOS battery causes clock and boot errors
There is a coin-sized battery on your motherboard, a CR2032, and it does one quiet job. It keeps the BIOS settings and the clock alive while the machine is unplugged.
When that cell dies, the symptoms are specific. The clock resets to a default date every time you cut the power. You get a message like CMOS checksum error or “system time not set” at switch-on. The machine may hang and ask you to press F1, or forget its boot order and swear there is no bootable drive when the drive is fine. A dead CMOS battery causes clock and boot errors, and it fools people into thinking their hard drive has failed.
The fix is a two dollar part. Power down, unplug, ground yourself, pop the old CR2032 out of its clip, and press a fresh one in the same way up, plus symbol facing out. On a desktop this is a sixty second job. On a laptop the cell is often buried under the board, and reaching it means a real teardown.
That teardown is the line for a lot of people, and there is no shame in stopping at it. If reaching the CMOS battery on your laptop means pulling the whole board and you are not comfortable there, hand it to a shop. Cheap part, short job for someone who does it daily.
Beep codes and what they mean
Older desktops, and a fair number of business laptops, talk to you when they cannot boot. They beep.
Those beeps are POST codes. The moment you power on, the system runs a power-on self test, and if something fails before the screen comes up, the internal speaker reports it as a pattern of beeps. Beep codes indicate a specific hardware fault, useful when you have no display to read an error from.
Here is the catch, and it matters more than the codes themselves. The patterns are not universal. They depend on your BIOS maker, usually AMI or Award/Phoenix, while Dell and Apple run schemes of their own. A pattern that means video on one board means memory on another. Do not trust a random chart you found on the first search result.
As a rough starting direction only, on a machine with a working speaker:
- No beep at all: often a power or motherboard fault, or a speaker that was never connected.
- One continuous or repeating beep: commonly RAM that is not seated or not detected. Go back and reseat it.
- One long beep then two or three short ones: frequently a video or graphics fault on many boards, though ASUS reads that same pattern as a memory error. This is exactly why you check your own manual.
- A steady high-low siren: often overheating or a CPU problem.
Treat those as a hint, not a verdict. Look up your exact motherboard or laptop model with the words “beep codes” and read the maker’s own table. Plenty of newer machines have no speaker at all and use a row of diagnostic LEDs or a two-digit code display instead, which you also decode from the manual. A machine that beeps and then dies under heat is worth reading about in how to fix an overheating laptop.
When to stop and pay a pro
Draw the line honestly. Reseating RAM, swapping a charger, draining flea power, changing a CR2032 on a desktop: all fair game for a careful beginner.
Anything that means suspecting the motherboard, reworking a connector, or a laptop teardown you already dread is where the math changes. If you have run the charger test, the power drain, and a RAM reseat and it is still dead, you have done the free checks a shop starts with anyway. Paying a technician now buys a diagnosis, not defeat.
And a hard stop: if you smell burning, see a swollen or bulging battery, or find liquid inside, unplug it and leave it alone. That is a safety problem, not a Saturday project.
The repair ticket
Symptom. Computer will not turn on. Either dead silent, or it powers on with a black screen.
Cause. No power usually traces to the charger, the outlet, the battery, or a hung power controller holding residual charge. No display usually traces to loose RAM, a dead CMOS battery, or a failing panel or cable. A hardware fault caught at POST may announce itself in beep codes.
Fix. Split the two branches first. For no power: test a known-good charger of the correct wattage, confirm the outlet, then drain the flea power by holding the button 30 seconds with the battery out. For no display: reseat the RAM one stick at a time, try an external monitor, and replace the CMOS battery if the clock keeps resetting. Read any beep pattern against your own model’s manual, never a generic chart. Still dead after the free checks? Pay for the diagnosis.