The monitor had been dying slowly for weeks: a longer and longer pause between hitting the power button and the panel actually lighting up, then a stretch of frantic clicking from somewhere inside, then nothing at all. By the time it stopped powering on entirely I'd half-decided it was landfill. Then I remembered what almost always kills consumer electronics of a certain age, and decided to open it up before I gave up.
It's nearly always the capacitors. The little electrolytic ones in the power supply section spend their lives hot, ripple current going through them, slowly drying out until they bulge and fail. Manufacturers fit cheap ones, the panel's fine, the backlight's fine, and the whole unit gets thrown away because of two components worth about thirty pence.
Sure enough, the moment the back was off, two capacitors near the main filter section were domed at the top instead of flat. Classic. One of them had even started to weep a bit of electrolyte down the side. The rest of the board looked perfect.
A word of caution before anyone follows along: a PSU holds a charge. Even unplugged, the big primary capacitor can keep a genuinely dangerous voltage for a good while. I unplugged it, left it sitting overnight, and still bled the big cap through a resistor before I put a finger anywhere near the board. Respect that bit or don't open it at all.
The repair itself was the easy part. Desolder the two swollen caps, note the polarity (the stripe is the negative leg, and getting it backwards makes them go bang), and fit replacements of the same capacitance and at least the same voltage rating. I went a bit higher on voltage and chose a 105°C-rated part rather than the 85°C originals, on the theory that the extra headroom is what they were short of in the first place. Maybe a fiver of components from the parts drawer.
Back together, power button, and it lit up first try with none of the dramatic clicking. That was a few weeks ago and it's been solid since.
I'm not pretending every fault is two bad capacitors. Sometimes it's the panel, or a control board, or something genuinely not worth chasing. But a bulging cap is so common, so cheap and so visible that it's daft not to look. Fifteen minutes with a screwdriver and an iron saved a working display from the skip, and saved me buying a new one to replace a fault that cost less than a coffee to repair.