Laptop won't turn on or black screen — step-by-step diagnosis

A laptop that won't start looks terminal but usually isn't. Most of the time it's one of a handful of problems — a dead battery, a sleep-mode issue, loose RAM, a failed display. Here's the order we diagnose in. Takes about 20 minutes to work through, and it'll tell you whether you're looking at a home fix or a workshop job.

Start by listening

First thing to check: when you press the power button, what actually happens?

• Nothing at all — no fans, no LEDs, no sound: power supply / charger / battery problem (section 1).
• LEDs light up briefly then go off: motherboard short or failed VRM.
• Power light on, fans spinning, but screen stays black: display or RAM issue (sections 3-5).
• Screen lights up but never boots past logo: storage or OS issue (not covered here — a different problem).

1. Power drain (fixes more cases than you'd think)

Laptops can get into a stuck power state where they won't respond even with the charger plugged in.

• Unplug the charger.
• If the battery is removable: take it out.
• Hold the power button down for 30 seconds with no power connected. This drains the capacitors on the motherboard.
• Put the battery back. Plug the charger in. Try to boot.

This fixes sleep-mode hangs, firmware glitches, and some charging-circuit lockups. It's the single most effective thing to try first.

2. Check the charger and DC jack

• Does the charger LED light up when plugged into the wall (without the laptop connected)?
• Does a charging LED appear on the laptop when you plug the charger in?
• Wiggle the DC jack on the laptop end — if LEDs flicker, the jack is damaged.
• Try a different (compatible) charger if you have one.

Common failure: the DC jack is soldered to the motherboard on most modern laptops; it cracks after years of cable movement. Symptom: charges only at a specific angle, or not at all.

3. External display test

If the laptop powers on (fans, lights, keyboard backlight) but the screen is black, the issue is display-side.

• Plug an HDMI cable into the laptop and into a TV or monitor.
• Power the laptop on.
• Wait 30 seconds then press the key combination to mirror display (usually Fn + F4, F5, F7 or F8 depending on brand — look for a monitor icon).

If the external display shows the Windows/Mac login screen, the laptop is fully working except for its built-in display. The fault is one of:

• LCD cable — cracked or disconnected. Common on laptops that have been opened/closed heavily.
• Backlight / inverter — in older laptops; shine a torch obliquely at the "black" screen and you can just make out a faint image, that's a backlight failure.
• LCD panel itself — physical damage, cracked internally.
• GPU switching issue — some laptops switch between integrated and dedicated GPUs; if the dedicated GPU has failed and the laptop can't fall back, you get black.

4. RAM reseat

If the laptop is still completely blank on external display too, loose RAM is a strong candidate. This fixes a remarkable number of "dead" laptops, especially older ones that have travelled.

• Power off, unplug, remove battery if possible.
• Find the RAM access panel on the underside (small rectangle held by 1-2 screws). Some ultrabooks have soldered RAM and no access — skip if so.
• Open the panel. You'll see 1-2 RAM sticks clipped into slots.
• Release the side clips so each stick pops up at 30°. Slide it out.
• Blow dust off with compressed air. Re-insert firmly at an angle until it clicks.
• Reassemble, power on.

If the laptop has two sticks, try booting with each one individually in slot 1 — isolates a single faulty stick.

5. CMOS reset

Rare but worth knowing. A bad BIOS setting can prevent boot. On most laptops:

• Unplug the charger.
• Remove the battery if removable.
• Hold power for 60 seconds.
• Some laptops have a small pinhole CMOS reset — check the service manual.

Reassemble and try.

6. Liquid exposure

If the laptop has ever had a spill — even if it "seemed fine afterwards" — corrosion on the motherboard is a strong candidate. Symptoms: worked normally, then one day didn't. Look under the keyboard for any sticky residue, discolouration or the tang of stale drink.

Liquid damage is a bench job. See our MacBook liquid spill guide — the first-response steps are the same for any laptop.

When to send it in

If power drain, different charger, external display and RAM reseat all fail, the fault is on the motherboard or a non-user-serviceable component (soldered RAM, embedded GPU, chipset). That's what the workshop is for. Post the laptop in — we'll diagnose for free, quote the specific fault, and most repairs turn around in a week. Common jobs we see: DC jack replacement, LCD cable swap, liquid-damage cleaning, GPU reflow.