A customer in Craigmillar brought in a four-year-old Lenovo IdeaPad last month with a complaint that always makes a tech sit up: the right third of the screen was completely dark. Not dim, not fuzzy — a clean vertical edge, with normal picture on the left side and nothing but black on the right. Everything else about the laptop worked. Windows loaded, the mouse moved, you could even see half of File Explorer. She had assumed the screen was finished and was ready to buy a new laptop.
It turned out to be an eDP cable that had been quietly pinching itself inside the hinge for four years, and the panel was still perfectly fine. The repair took under an hour. That case is a good one to walk through because “half the screen is dark” actually covers four completely different faults — and only one of them is a dead panel. If you can tell them apart in the first ten minutes, you avoid replacing hardware that was never broken.
What “Half Dark” Actually Looks Like
Before anything else, be precise about what you are seeing. A properly half-dark laptop screen has a clean, straight vertical or horizontal edge between the lit area and the dark area, and nothing on the dark side responds to anything you do. Mouse cursors vanish into it, open windows disappear into it when you drag them across. That is a different symptom from a dim half, from a tinted half (pink or green), from vertical coloured lines, and from flickering — each of those points at a different fault.
Look at the dark area in a well-lit room with a torch held an inch from the panel. If you can faintly see the Windows desktop under the torch beam — icons, windows, the mouse pointer — the LCD itself is still being driven, and only the backlight behind that half is dead. If the torch shows nothing at all, no faint ghost of the desktop, the picture signal is not reaching that side of the panel. Those two outcomes point in different directions and the rest of the diagnosis depends on which one you got. Our earlier walk-through of the torch test on a fully black laptop screen covers the same technique from the other end, when the whole display looks dead.
Suspect One: A Loose or Damaged Video Cable
By a long way the most common cause of a half-dark laptop screen is the thin flat flex cable that runs from the mainboard, up through the hinge, and into the back of the panel. Depending on the model this is called an LVDS cable or an eDP cable, and modern laptops carry the whole image down just four or six tiny differential pairs. If one of those pairs loses contact or wears through, you lose half the picture while the other half carries on normally.
The giveaway is movement. Open and close the lid slowly while the laptop is running. If the dark half flickers back to life at a certain angle, flashes briefly as the lid moves, or appears and disappears when you press on the plastic bezel next to the hinge, you have a cable fault. The hinge end wears first because that is where the cable flexes every time the lid moves, and after three or four years of daily opening it is not unusual to see the insulation worn through on at least one conductor.
On most laptops this is a cheap, bench-only repair. The cable is a few pounds, the labour is removing the bezel, routing the new cable through the hinge, and reseating the two connectors. The panel itself does not need to be touched. This is the single biggest reason not to replace a laptop just because “the screen is broken” — a thirty-pound cable can save a working panel that would otherwise be scrapped.
Suspect Two: A Dead Backlight on One Side
If the torch test showed a faint desktop behind the dark half, the LCD is still being told what to display. What has died is the lighting behind it. Most laptop panels are edge-lit, meaning a thin strip of LEDs runs along one edge of the display and shines sideways into a light-guide that spreads the light evenly across the panel. If a section of that LED strip fails, or the strip’s driver fails, half the panel goes dark while the LCD underneath is still working perfectly.
This one is awkward. On a desktop monitor the backlight is often an independent board you can replace. On a modern laptop the LED strip is bonded inside the panel assembly and there is no honest way to replace just the strip without destroying the panel in the process. The practical answer is a whole-panel replacement — keeping the lid, hinges, cable and bezel, and swapping the display assembly behind them. Our laptop screen replacement service page covers how we source a matching panel for the model and the pitfalls of fitting the wrong revision.
Suspect Three: A Failing TCON Board
Every LCD panel has a small board called the timing controller, or TCON, which translates the eDP signal from the laptop into the row-and-column driving signals the LCD itself needs. The TCON is physically part of the panel, usually behind a strip of metal on one edge. When half of the TCON fails, you often see exactly the symptom this article is about: a clean vertical split with the left half of the picture working and the right half completely dark — or, more rarely, bright white.
The telltale sign of a TCON fault, rather than a cable fault, is that nothing changes when you flex the lid. The dark half stays dark whether the laptop is open ninety degrees or almost closed, and pressing the bezel does nothing. Hooking the laptop up to an external monitor over HDMI or USB-C shows a perfect picture on the external screen, which rules out the graphics chip and the cable in one test. Our walkthrough on the external monitor test for a laptop display explains exactly what that test does and does not prove.
A failed TCON is not independently repairable in the field. The panel is replaced as a unit. The good news is that it is still just a panel swap, not a mainboard job — the laptop itself is fine.
Suspect Four: A Hinge-Pinched Cable (The Craigmillar Case)
The Craigmillar laptop at the top of this article was a classic version of this: the eDP cable had been slowly compressed inside the hinge over four years, and one of the differential pairs had broken contact. The symptom was identical to a dead TCON — a clean vertical split, dark right side, no response to lid flex — but the fix was a cable, not a panel.
The only way to tell those two apart cleanly is to open the laptop and inspect the cable at the hinge end. On the bench this takes a few minutes. If the insulation is split, worn or kinked, the cable is replaced and the panel is almost always fine. If the cable looks perfect and the symptom persists, the panel comes out next. That is the honest sequence — start with the cheapest fix that could possibly explain what you are seeing, and only move up the chain if it does not.
Confirming It Is Not the Graphics Chip
Before any screen work, confirm the fault is in the display path rather than the laptop itself. Plug the laptop into an external monitor using HDMI or USB-C and set Windows to extend the desktop. If the external monitor shows a full, clean picture across its whole area, the graphics chip and the Windows side are fine, and the fault is somewhere between the mainboard’s display connector and the panel — which is the cable or the panel itself. If the external monitor also shows a half-dark image, then it is the graphics chip or a software corruption, and the panel is innocent. That is a different and more serious problem, and board-level laptop repair rather than a screen swap.
While you are testing, boot into the laptop’s BIOS or UEFI setup — usually by holding F2 or Delete at power-on — and see whether the dark half is dark there too. The BIOS screen is drawn by firmware before Windows loads, so if the fault is identical in BIOS, Windows is not involved and this is hardware. We have seen one in twenty cases where a corrupted graphics driver mimicked a hardware fault, and the BIOS check is what caught it.
When It Isn’t Worth Fixing
Not every half-dark laptop is worth repairing. If the laptop is seven or eight years old, running a slow mechanical hard drive, has already had its battery replaced once, and the screen fault turns out to be a whole-panel job, the sensible answer is often to copy the data off and recycle the machine responsibly rather than pour money into it. We will say that plainly before any work starts, and we will not quote on a fix we would not do ourselves. The repair-vs-replace guide for cracked laptop screens walks through the same decision from a different starting point.
On the other hand, a two or three-year-old laptop with a strong CPU, an SSD, and a half-dark screen is almost always worth saving — especially if the fault turns out to be a cable, which is the cheapest category of repair we do. The general laptop repair service page covers how we quote these before touching anything.
Bringing a Laptop In From Craigmillar
If you are in Craigmillar, Newcraighall, Niddrie, Duddingston or the wider south-east Edinburgh side — EH15, EH16, EH17 — and your laptop screen has gone half dark, bring it in and we will run the ordered test above in front of you: torch test, lid-flex test, external monitor, BIOS check. Within about fifteen minutes you will know whether this is a cable, a backlight, a TCON or something deeper, and we will tell you what the honest fix is and whether it is worth doing. Our local screen replacement service for Craigmillar page has the collection details for the area.
If the panel does need replacing, we will show you the matching replacement part before it goes in and keep the old assembly for you to see when you collect. If it is a cable, you keep the panel — and if the honest answer is that the laptop is not worth it, we will tell you that too and talk you through the data-recovery and recycling side instead.
Book a diagnostic online or get in touch and we will take a proper look.
Last updated: 12 October 2026