Used SFX Power Supply Guide: Corsair SF Series, Cooler Master V SFX & Buying Tips
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When assembling a Small Form Factor (SFF) or Mini-ITX build in the UK, the power supply is often the hardest pill to swallow. While full-sized ATX power supplies are plentiful and cheap, high-density SFX (Small Form Factor) power supplies routinely command £120 to £180 brand new. Packing 750 Watts of power, active PFC, and Japanese capacitors into a metal brick no larger than a stack of index cards requires premium engineering.
Fortunately, the UK second-hand market offers immense savings. Top-tier SFX units from Corsair, Cooler Master, and Lian Li trade for between £50 and £95. However, because SFX units operate in cramped cases with limited airflow, evaluating fan bearing wear and verifying modular cable compatibility is paramount.
UK Second-Hand SFX Power Supply Hierarchy
| Model & Wattage | Efficiency Badge | Acoustic Fan Profile | Typical UK Used Price | Verdict |
|---|---|---|---|---|
| Corsair SF750 Platinum (Classic Black) | 80+ Platinum | Zero-RPM up to 300W (Dead Silent) | £90 – £115 | The Undisputed SFF King |
| Corsair SF600 Platinum / Gold | 80+ Platinum / Gold | Quiet fluid dynamic bearing | £55 – £75 | Best Value for 65W CPU + RTX 3070 |
| Cooler Master V650 / V750 / V850 SFX Gold | 80+ Gold | Aggressive fan ramp (V1 noisy, V2 quiet) | £50 – £70 | Solid Budget Workhorse (Get V2) |
| Lian Li SP750 / SP850 SFX | 80+ Gold | Slightly audible above 400W | £60 – £75 | Includes 12VHPWR on newer batches |
| SilverStone SX-series (SFX-L) | 80+ Gold / Titanium | 120mm slim fan (Longer 130mm body) | £45 – £65 | Check case clearance (SFX-L is longer) |
For general power supply safety considerations, consult our Used PSU Tier List & Safety Guide.
SFX vs SFX-L: Don't Get Caught by Length Clearances
Always verify that the model number does not end in “-L” unless you have checked your specific PC case clearance manual.
The 4 Critical Inspection Checks for Used SFX PSUs
1. Verify Short-Length Modular Cables
SFX power supplies ship from the factory with shortened ribbon cables (typically 300mm to 350mm) engineered for compact cases. If a seller swapped in standard 650mm ATX cables from an old power supply, routing them inside an ITX case will be virtually impossible. Ensure the original short cables are present.
2. Check for the ATX-to-SFX Adapter Plate
Reputable SFX power supplies include a stamped steel adapter bracket that allows the tiny SFX unit to be mounted into standard ATX case power supply cutouts. Confirm the seller includes this bracket.
3. Listen for Fan Motor Chirp & Bearing Wear
Because SFX units use smaller 92mm fans, the fan must spin faster to dissipate heat under heavy load. In budget units (like the early revision Cooler Master V SFX), the fan curve featured an annoying cycling bug where the fan spun up to 100% every 30 seconds at idle. Verify quiet fan operation.
4. Check for Recall Serial Numbers (Corsair SF Series)
In 2020, Corsair issued a voluntary recall for select SF-series units manufactured between lot codes 194448xx to 201148xx due to a component failure when exposed to high heat and humidity. Check the barcode on the side label to ensure the unit is outside this date range or has a factory green dot recall pass sticker.
Frequently Asked Questions
Can a 600W SFX power supply run an RTX 3080 or RTX 4070 Ti?
A Tier-A 600W unit like the Corsair SF600 Platinum will comfortably run an RTX 4070 Ti or RTX 4070 Super paired with a 65W Ryzen CPU. However, for a 350W RTX 3080 with high transient spikes, the SF750 is strongly recommended to prevent over-current shutdowns.
Are generic SFX power supplies on eBay safe?
Never buy unbranded grey-box SFX power supplies. Squeezing high wattage into compact enclosures requires premium cooling and safety topology. Stick strictly to Corsair, Seasonic, Cooler Master, SilverStone, or Lian Li.
Do SFX power supplies support the newer ATX 3.0 / 12V-2x6 standard?
Modern 2024–2026 revisions (like the Corsair SF850 / SF1000 ATX 3.1) include native 12V-2x6 micro-fit cables. Older used units use standard 8-pin PCIe cables and connect to RTX 40-series cards using the 2x 8-pin to 16-pin adapter included with the GPU.
Source Used SFX Power Supplies on Koukan
Trade tested Corsair SF and Cooler Master SFX units backed by escrow payment security. Test fan curves and rail voltages at home before payment is disbursed.
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