What Was Happening
The OMEN had been running fine and then simply didn’t turn on one day. Not a crash, not a blue screen — nothing. Pressing the power button produced no fans, no lights, no beeps, no flicker. Completely inert.
That total silence is actually useful information. A machine that lights up and then fails, or gets partway through boot and stops, is telling you something is starting and then going wrong. A machine that does nothing at all when you press power has almost always lost its power delivery — and on a desktop that means the wall supply, the cable, the power supply unit inside, or the front-panel button, in roughly that order of likelihood.
The owner’s worry was the graphics card or motherboard, because on a gaming build those are the parts that hurt to replace. Before going anywhere near that conclusion, the job was to find out whether power was even reaching the components.
Our Diagnosis
Dead-desktop diagnosis is methodical and cheap when you do it in the right order:
- Confirm power at the wall and cable. Swapped in a known-good kettle lead and a socket we’d tested. Still nothing. So the machine was genuinely getting mains power and still not responding.
- Rule out the front-panel power button. A failed power switch or its header can mimic a dead machine. We briefly bridged the motherboard power header directly. No response — so the button wasn’t the issue, and the fault was further in.
- Test the power supply on its own. The PSU is the next suspect and it can be tested in isolation, disconnected from everything else, with a simple bridging test on the main connector. A healthy supply spins its own fan and produces its output rails. This one did nothing — no fan, no rails. The power supply was dead.
- Confirm nothing downstream had been taken with it. This is the step that matters and the one that gets skipped. A power supply can fail quietly, or it can fail in a way that damages what it’s connected to. We tested the motherboard, drive and graphics card on a known-good bench supply before ordering the part. Everything else powered up and posted normally. The failure was contained to the PSU.
Conclusion: a straightforward dead power supply, with the rest of the machine healthy. The expensive parts the owner was worried about were fine.
How We Fixed It
Fitted a correctly rated replacement power supply. “Correctly rated” is doing real work in that sentence. A gaming desktop with a dedicated graphics card draws serious peak power, and the replacement has to have the headroom and the right connectors for that card, not just enough wattage to make the machine switch on. We matched the unit to the actual load of this build rather than the cheapest thing that fits the hole.
Reconnected and cable-managed properly. In a desktop, tidy cabling isn’t cosmetic — trailing cables near fans and airflow paths cause their own problems later. Everything was routed and secured on the way back together.
Stress-tested under load. A power supply can seem fine at idle and then fault when the graphics card is actually pulling hard. We ran the machine under sustained load — the kind a game produces — and watched that it stayed stable, cool and up, rather than just confirming it reached the desktop and calling it done.
The Result
The OMEN powers on the moment you press the button and boots normally, and it held rock-steady through the load testing. Because the failure hadn’t spread beyond the power supply, this stayed one of the cheaper desktop repairs — a single part and the labour to prove the rest of the machine was sound. The owner kept the graphics card, the storage and everything on it.
Why This Happens
Power supplies are, quietly, one of the hardest-working and most-overlooked parts in any desktop. They run whenever the machine is on, they deal with the messiness of mains electricity, and they’re full of components — capacitors especially — that age and eventually give out. A PSU that’s several years old, or that was under-specced for the machine to begin with, is a very common cause of a desktop that suddenly won’t turn on.
Gaming machines see this more than most. A dedicated graphics card can more than double a system’s power draw under load, and a supply that was only just adequate spends its life running near its limit. Cheap or underrated units bought to save money on a build are a frequent reason a genuinely capable PC dies earlier than it should.
The good news is that, caught in isolation, a failed power supply is one of the more affordable desktop faults. The reason it’s worth having diagnosed rather than just swapping the part yourself is that occasional case where the supply failed destructively and damaged something it was connected to. Testing the rest of the machine before and after the swap is what separates “replaced a part” from “confirmed the repair.”
Local Help in Putney SW15
If your desktop has gone completely dead — no fans, no lights, no response — it’s worth having the power side checked before assuming the worst about the expensive components. More often than not the fault is contained to the power supply, and the graphics card and storage are perfectly fine.
We repair, upgrade and build desktops — gaming rigs included — from our Putney workshop in SW15. We diagnose first, tell you honestly whether the machine is worth the fix, and test under real load before it goes home.
Drop in to SW15, call 020 7610 0500, or use the contact form.