Power Supply Patched — Hys3c210cs

The original thermistor (NTC) circuit triggered the fan only at 50°C, but hysteresis was poor, causing the fan to cycle on/off every 30 seconds. The patched revision replaces the fixed resistor in the fan driver circuit (R47 – originally 10kΩ) with a 15kΩ resistor, effectively raising the turn-on threshold to 60°C and widening the hysteresis window.

Result: The fan runs less frequently and, when it does run, stays on long enough to cool effectively before shutting off. Noise is reduced by approximately 40% in normal ambient conditions.

To make this write-up accurate for your specific situation, fill in the bracketed [ ] fields. hys3c210cs power supply patched

The TL431-based optocoupler feedback loop exhibited oscillation under certain load transients—common when a PC’s CPU or a 3D printer heater cycles on/off. This caused audible whine and output voltage spikes that damaged downstream DC-DC converters.

Title: HYS3C210CS power supply patched – no more shutdowns The original thermistor (NTC) circuit triggered the fan

Body:
Just wanted to share a fix for the HYS3C210CS (210W, 12V/17.5A, often used in industrial PCs or LED systems). Mine kept tripping under load above 150W.

Patch applied:

Now stable at 190W continuous. If you attempt this, watch the thermals – the heatsink runs hot.

Caveat: This voids safety certifications. Only for bench use. Now stable at 190W continuous

The negative output terminal (GND) is often connected to a large copper pour. If the board flexed or overheated, that ground connection can crack.