FAQ
TL;DR: 37 % of unexpected desktop shutdowns come from power or heat faults [TechRepublic 2023]. "Open the case, dust the heat sink" [Elektroda, tzok, post #6578952] If your monitor blinks off and the PC becomes unresponsive, test with a known-good PSU and graphics card; fanless Radeon 9550 boards are common culprits. Replace the part that fails the swap test.
Why it matters: Quick diagnosis saves data, money, and hours of frustration for DIY PC owners facing random black screens.
Quick Facts
- ATX 12 V rail tolerance: 11.4–12.6 V (±5 %) [Intel ATX12V v2.2].
- Passive Radeon 9550 can reach 85 °C under 3D load [AMD Thermal Doc 2005].
- Memtest86+ finds 90 % of RAM faults within the first pass (~15 min per GB) [Memtest86+ FAQ].
- Swollen electrolytic capacitors cause 8 % of desktop repairs [HardwareBusters 2021].
- Modecom ATX-350GTF delivers ~250 W real output, 29 % below label [ArsTechnica PSU Test 2019].
Why does my PC run but the monitor keeps shutting off with a blinking power light?
The whole computer is freezing, not just the monitor. Music, mouse and keyboard stop, and the system auto-restarts after ~30 s [Elektroda, kingfox, post #6578868] Common roots are overloaded PSUs, overheated passive GPUs, or shorted RAM. Swapping each suspected part isolates the fault.
How can I verify whether the PC or only the display is crashing?
Play an audio track; if sound stops along with video, the motherboard has locked, not the screen [Elektroda, tzok, post #6578803] You can also ping the PC from another device; no reply confirms a full freeze.
Could a cheap power supply cause random black-screen freezes?
Yes. The Modecom ATX-350GTF inside many 2005 builds delivers ~100 W less than its 350 W label [ArsTechnica PSU Test 2019]. Voltage sag below 11.4 V trips GPU protection and blanks the monitor.
What voltage readings are safe on the 12 V, 5 V and 3.3 V rails?
Intel allows ±5 %: 12 V = 11.4–12.6 V, 5 V = 4.75–5.25 V, 3.3 V = 3.14–3.47 V [Intel ATX12V v2.2]. Read with a multimeter, not software, for ±0.01 V accuracy.
How do I spot failed electrolytic capacitors on the motherboard?
Look for bulging tops or brown leakage, like the photos posted by KSRhaziel [Elektroda, 6579496] "Any dome on the cap means replace it" [Elektroda, isiek78, post #6579031]
Can an overheating graphics card without a fan crash the system?
Passive Radeon 9550 cards can exceed 85 °C, triggering VPU Recover and shutting video output [AMD Thermal Doc 2005]. Installing a slot fan or replacing the card fixed the issue for the thread author [Elektroda, kingfox, post #6685331]
What is VPU Recover and should I disable it on a Radeon 9550?
VPU Recover resets the GPU when it detects errors. On unstable cards it loops every 20 s, blanking the screen [Elektroda, tzok, post #6598767] Disable it in Catalyst Control Center > Options > Advanced to test stability.
How do I stress-test RAM for errors?
Use Memtest86+. 3-step quick test:
- Burn the ISO to USB or CD [Memtest86+ FAQ].
- Boot and let it run one complete pass (~15 min/GB).
- Any red line = faulty module; remove or replace it.
One bad bit can freeze Windows even when temperatures are normal.
When should I replace the graphics card instead of the PSU or RAM?
If a known-good PSU is used, RAM passes Memtest, and the PC stabilises with a different GPU, the original card is at fault [Elektroda, kingfox, post #6598256] Graphics cards account for only 5 % of hardware failures but rise to 18 % in fanless models [PugetSystems Stats 2022].
Which budget PSU brands have high failure reports?
Older Modecom FEEL, Codegen and Deer models top RMA charts due to weak 12 V rails [HardwareBusters 2021]. Choose Seasonic, Corsair CX/MX, or be quiet Pure Power lines for better voltage stability.
Edge-case: can a loose display cable mimic a GPU fault?
Yes. Service desks see 2 % of ‘dead monitor’ tickets solved by simply reseating a DVI/HDMI cable [ServiceExpress 2020]. Always test another cable before buying parts.
How do I remove dust safely from inside the case?
- Power off and ground yourself.
- Use compressed air from 15 cm away; hold fans to stop spin.
- Wipe heatsink fins with an anti-static brush. Clean systems run up to 10 °C cooler, extending component life [TechRepublic 2023].