--- title: "How to Fix PC Power Supply (PSU) Problems | FixFix Labs" description: "Diagnose power supply issues causing shutdowns, instability, or failure to boot. Step-by-step desktop pc troubleshooting guide with quick checks and fix inst..." lang: en json-ld: | [ { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://fixfixlabs.com/#organization", "name": "FixFix Labs", "url": "https://fixfixlabs.com/", "logo": "https://fixfixlabs.com/emblem.webp", "sameAs": [ "https://facebook.com/fixfixlabs", "https://instagram.com/fixfixlabs", "https://www.tiktok.com/@fixfixlabs.com" ], "alternateName": [ "fixfixlabs", "Fix Fix Labs", "FixFix Labs", "fixfix labs", "fixfixlabs.com", "FixFix Labs Luton" ], "address": { "@type": "PostalAddress", "streetAddress": "159 Marsh Road", "addressLocality": "Luton", "addressRegion": "Bedfordshire", "postalCode": "LU3 2QL", "addressCountry": "GB" }, "areaServed": "GB" }, { "@type": [ "LocalBusiness", "ProfessionalService" ], "@id": "https://fixfixlabs.com/#localbusiness", "name": "FixFix Labs", "alternateName": [ "Repair Zone", "Repair Zone Luton", "FixFix Labs Luton", "FixFix Labs" ], "url": "https://fixfixlabs.com/", "image": "https://fixfixlabs.com/emblem.webp", "telephone": "+441582505020", "email": "support@fixfixlabs.com", "priceRange": "££", "parentOrganization": { "@id": "https://fixfixlabs.com/#organization" }, "address": { "@type": "PostalAddress", "streetAddress": "159 Marsh Road", "addressLocality": "Luton", "addressRegion": "Bedfordshire", "postalCode": "LU3 2QL", "addressCountry": "GB" }, "areaServed": [ "Luton", "Marsh Road", "Bury Park", "Leagrave", "Limbury", "Biscot", "Sundon Park", "Marsh Farm", "Lewsey", "High Town", "Stopsley", "Wigmore", "Farley Hill", "Round Green", "Bramingham", "Dunstable", "Houghton Regis", "Caddington", "Slip End", "Barton-le-Clay" ], "openingHoursSpecification": [ { "@type": "OpeningHoursSpecification", "dayOfWeek": [ "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" ], "opens": "10:00", "closes": "18:00" } ], "sameAs": [ "https://facebook.com/fixfixlabs", "https://instagram.com/fixfixlabs", "https://www.tiktok.com/@fixfixlabs.com" ] }, { "@type": "WebSite", "@id": "https://fixfixlabs.com/#website", "name": "FixFix Labs", "url": "https://fixfixlabs.com/", "publisher": { "@id": "https://fixfixlabs.com/#organization" }, "inLanguage": "en-GB", "potentialAction": { "@type": "SearchAction", "target": { "@type": "EntryPoint", "urlTemplate": "https://fixfixlabs.com/device-troubleshooting?q={search_term_string}" }, "query-input": "required name=search_term_string" } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://fixfixlabs.com/" }, { "@type": "ListItem", "position": 2, "name": "Troubleshooting", "item": "https://fixfixlabs.com/device-troubleshooting" }, { "@type": "ListItem", "position": 3, "name": "Desktop PCs Guides", "item": "https://fixfixlabs.com/device-troubleshooting#pc" }, { "@type": "ListItem", "position": 4, "name": "PC Power Supply (PSU) Problems", "item": "https://fixfixlabs.com/device-troubleshooting/pc-psu-issues" } ] }, { "@context": "https://schema.org", "@type": "HowTo", "name": "PC Power Supply (PSU) Problems", "description": "This guide helps diagnose power supply issues in desktop PCs, from complete failure to boot to intermittent shutdowns and instability.", "url": "https://fixfixlabs.com/device-troubleshooting/pc-psu-issues", "step": [ { "@type": "HowToStep", "position": 1, "name": "Paperclip test", "text": "1. Unplug PSU from all components.\n2. Find the 24-pin motherboard connector.\n3. Bridge the green wire (PS_ON) to any black wire (ground) with a paperclip.\n4. Plug PSU into wall and switch on.\n5. If fan spins, PSU has basic power. If not, PSU is dead." }, { "@type": "HowToStep", "position": 2, "name": "Check all internal connections", "text": "1. Power off and unplug.\n2. Reseat the 24-pin motherboard connector.\n3. Reseat the 4/8-pin CPU power connector.\n4. Check GPU power connectors.\n5. Ensure all modular cables are firmly connected at both ends." }, { "@type": "HowToStep", "position": 3, "name": "Test with minimal components", "text": "1. Disconnect everything except CPU, one RAM stick, and motherboard power.\n2. Try to boot.\n3. If it works, add components back one at a time.\n4. This isolates which component is causing the issue." }, { "@type": "HowToStep", "position": 4, "name": "Calculate power requirements", "text": "1. Use an online PSU calculator.\n2. Add up all component power draws.\n3. Add 100-200W headroom.\n4. If your current PSU is below this, upgrade.\n5. Choose 80 PLUS Bronze or Gold rated units." }, { "@type": "HowToStep", "position": 5, "name": "Replace the PSU", "text": "1. Purchase a PSU with adequate wattage and good rating.\n2. Power off and unplug the PC.\n3. Disconnect all PSU cables from components.\n4. Remove old PSU from case.\n5. Install new PSU and reconnect all cables." } ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Does the PC show any sign of life when pressing power?", "acceptedAnswer": { "@type": "Answer", "text": "Yes: PSU is providing some power. Issue may be with specific rails or motherboard. | No: PSU may be completely dead, or the power button connection is faulty." } }, { "@type": "Question", "name": "Does the PC shut down randomly under load?", "acceptedAnswer": { "@type": "Answer", "text": "Yes: PSU may lack sufficient wattage or be failing under stress. | No: If shutdowns happen at idle, it could be a different issue." } }, { "@type": "Question", "name": "Do you smell burning from the PSU area?", "acceptedAnswer": { "@type": "Answer", "text": "Yes: Immediately unplug the PC. The PSU has likely failed and may damage other components. | No: Electrical fault is less likely but not ruled out." } } ] } ] --- [![FixFix Labs](/assets/fixfix-logo-Dj0uNxZh.webp)](/) [Troubleshooting](/device-troubleshooting) [Luton Repairs](/repair) [Repair by Post](/mail-in-repair)[Track Repair](/track) [Custom PCs](/custom-builds) [Sign In](/login)[Start Diagnosis](/diagnosis) [](tel:01582505020) [01582 505020](tel:01582505020) 1. [All Guides](/device-troubleshooting) 2. [Desktop PCs](/device-troubleshooting?category=pc#problems) 3. PC Power Supply (PSU) Problems Desktop PCs psu # PC Power Supply (PSU) Problems ## Quick Answer This guide helps diagnose power supply issues in desktop PCs, from complete failure to boot to intermittent shutdowns and instability. Please note: This guide is provided for informational purposes only. Any steps you choose to follow are at your own discretion and risk. If you're unsure, we recommend booking a professional diagnosis. Line illustration of a desktop tower and monitor with diagnostic reference markings, overlaid with a power-state indicator with pulse markers Desktop PC — illustration On this page - [Quick Checks](#quick-checks-heading) - [Guided Troubleshooting](#diagnostic-heading) - [Possible Causes](#possible-causes-heading) - [Self-Fix Instructions](#self-fix-heading) - [Safety Warnings](#warnings-heading) - [When troubleshooting isn't enough](#next-steps-heading) ## Quick Checks Try these fast checks first — they solve most cases. 1. Check power cable Ensure the mains cable is firmly connected to the PSU and wall outlet. 2. Test the wall outlet Plug another device into the same outlet to verify it works. 3. Check PSU switch Ensure the PSU power switch on the back is in the ON position. 4. Listen for fan spin on startup If PSU fan does not spin at all, the PSU may be dead. ## Guided Troubleshooting Answer these questions to narrow down the issue. Does the PC show any sign of life when pressing power? YesNo Does the PC shut down randomly under load? YesNo Do you smell burning from the PSU area? YesNo ## Possible Causes Faulty power cable Common Damaged or loose mains cables prevent power delivery. PSU failure Common Capacitors and components inside PSUs degrade over time. Insufficient wattage Moderate Upgraded GPU or CPU may exceed PSU capacity. Faulty PSU switch Less Common The rear switch can fail or have poor contact. Overheating PSU Moderate Dust buildup or poor ventilation causes PSU to overheat and shut down. Damaged internal cables Less Common Modular PSU cables can become damaged or loose. If the cause requires professional attention, see [Get Desktop PC wont turn on fixed](/repair/pc/wont-turn-on). ## Self-Fix Instructions Safe steps you can try at home. 1. ### Paperclip test 1\. Unplug PSU from all components. 2. Find the 24-pin motherboard connector. 3. Bridge the green wire (PS\_ON) to any black wire (ground) with a paperclip. 4. Plug PSU into wall and switch on. 5. If fan spins, PSU has basic power. If not, PSU is dead. 2. ### Check all internal connections 1\. Power off and unplug. 2. Reseat the 24-pin motherboard connector. 3. Reseat the 4/8-pin CPU power connector. 4. Check GPU power connectors. 5. Ensure all modular cables are firmly connected at both ends. 3. ### Test with minimal components 1\. Disconnect everything except CPU, one RAM stick, and motherboard power. 2. Try to boot. 3. If it works, add components back one at a time. 4. This isolates which component is causing the issue. 4. ### Calculate power requirements 1\. Use an online PSU calculator. 2. Add up all component power draws. 3. Add 100-200W headroom. 4. If your current PSU is below this, upgrade. 5. Choose 80 PLUS Bronze or Gold rated units. 5. ### Replace the PSU 1\. Purchase a PSU with adequate wattage and good rating. 2. Power off and unplug the PC. 3. Disconnect all PSU cables from components. 4. Remove old PSU from case. 5. Install new PSU and reconnect all cables. ## Safety Warnings - Never open a PSU. Internal capacitors hold dangerous charge even when unplugged. - If you smell burning, unplug the PC immediately and do not use it. - A failing PSU can damage other components. Replace promptly if issues are confirmed. - Always use the cables that came with your PSU. Do not mix cables between different PSU models. For a desktop with no power or a suspected PSU fault, start outside the case: confirm the mains cable, wall outlet and PSU rear switch, then note whether any fans or lights appear and whether shutdowns happen mainly under load. Burning smell or smoke is a stop condition, not a reason for more testing. ## Safe PSU checks before deeper diagnosis 1. 01 Reseat the mains power cable at the desktop and wall outlet. 2. 02 Test the wall outlet with another device and check that the PSU rear switch is in its normal on position. 3. 03 Press the power button once and note whether fans, lights or other signs of power appear. 4. 04 If the desktop starts but shuts down, note whether the shutdown happens mainly during heavier use or also while idle. 5. 05 If the no-power fault began after a major hardware upgrade, record what changed so the system's power requirements can be checked during diagnosis. ## Does a dead desktop prove the PSU has failed? No. A completely dead desktop can still have causes outside the power supply, so the PSU should not be condemned from the symptom alone. One possibility is the external cable or outlet; another is a fault elsewhere in the system power path. We would confirm PSU power delivery with safe diagnostic equipment before recommending replacement. ## PC no-power and PSU questions ### What can cause a PC not to turn on when the PSU is suspected? ### Can a no-power PC be repaired? ### How long does a PC no-power repair take? ### Is my data safe during a PC no-power repair? Never open a power supply unit The existing guide warns that a PSU can retain dangerous electrical charge even when unplugged. If you smell burning or see smoke, disconnect mains power and do not continue testing the computer. ## Related repairs - [PC / Desktop repair](/repair/pc) - [PC / Desktop power issue repair](/repair/pc/wont-turn-on) ## More troubleshooting guides - [PC Build Guide - Choosing Components](/device-troubleshooting/pc-build-guide) - [PC Case and Housing Airflow](/device-troubleshooting/pc-housing-airflow) - [PC GPU Not Detected or Crashing](/device-troubleshooting/pc-gpu-issues) ## When troubleshooting isn't enough If these steps didn't resolve the issue, a professional diagnosis can identify the root cause. [Start Diagnosis ](/diagnosis?category=pc&issue=wont-turn-on)[Get Desktop PC wont turn on fixed ](/repair/pc/wont-turn-on) ### Still need help? FixFix Labs repairs devices in Luton. Walk in to 159 Marsh Road, Luton, LU3 2QL — or book a slot online. Same-day service on most common repairs. 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