---
title: 'Replacing the PSU fan MOSFET on the Snapmaker U1'
url: 'https://blog.s0.is/blog/replacing-the-psu-fan-mosfet-on-the-snapmaker-u1'
markdown: 'https://blog.s0.is/blog/replacing-the-psu-fan-mosfet-on-the-snapmaker-u1.md'
date: '2026-10-14'
description: "While testing extra cooling fans for the Snapmaker U1 (this design isn't perfect, but it's way better than stock situation), I accidentally blew up the FET on the PSU daughterboard which switches the PSU fan (and, if you split it out like I did, the mainboard cavity fan too). By a stroke of luck, I…"
---

# Replacing the PSU fan MOSFET on the Snapmaker U1

While testing extra cooling fans for the Snapmaker U1 ([this design](https://makerworld.com/en/models/2793795-snapmaker-u1-improved-psu-and-motherboard-cooling) isn't perfect, but it's way better than stock situation), I accidentally blew up the FET on the PSU daughterboard which switches the PSU fan (and, if you split it out like I did, the mainboard cavity fan too).

By a stroke of luck, I discovered it is absurdly easy to replace this FET with a way beefier and common logic-level TO-220 N-channel MOSFET. In my case, the FQP30N06L, but any with pins in G-D-S order when viewed from the top should work. ![2026-10-14T19:20:50](https://blog.s0.is/user/pages/03.blog/04.replacing-the-psu-fan-mosfet-on-the-snapmaker-u1/2026-10-14T19:20:50.png "2026-10-14T19:20:50")

After removing the board, I first desoldered the husk of the shorted MOSFET.

I then mounted the replacement on the underside of the PCB close to the edge, approximately centred on the old footprint, using a piece of thin double-side VHB tape (great stuff). You could use any insulating double-sided tape, or silicone glue -- as long as it doesn't short to the test points below! There's lots of clearance underneath this PCB in the case because of how it connects to the PSU terminal block. ![IMG_4352_preview](https://blog.s0.is/user/pages/03.blog/04.replacing-the-psu-fan-mosfet-on-the-snapmaker-u1/IMG_4352_preview.jpeg "IMG_4352_preview")

Bending each of the legs around, I brought them over to the 3 solder points shown here. ![IMG_4351_preview](https://blog.s0.is/user/pages/03.blog/04.replacing-the-psu-fan-mosfet-on-the-snapmaker-u1/IMG_4351_preview.jpeg "IMG_4351_preview")

On the left, the Source pin is connected to the GND net by soldering to the nearest leg of the optocoupler.

Next, the Drain pin is connected to the leftmost pad of the SOT23 footprint which was the old MOSFET. This then connects up via a trace to the fan connector.

The Gate pin is soldered to the nearest pad on the pulldown resistor for the gate signal.

Then that's done!

(Actually, I then added an inductor on top of the FET and a capacitor on the fan connector, to make an LC filter for my fans. But you really shouldn't need it.)

---

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