Zalman 120mm Case Fan, Clear with Blue LED (ZA1225CSL)

After years of faithful service, this particular cooling fan has worn down to a point where it would vibrate noisily, its associated friction dragging down fan blade speed. Time for me to retire it but not before subjecting it to a teardown.

Sticker on the back says it is a Zalman model ZA1225CSL.

This particular fan was cast in clear plastic and has embedded blue LEDs for visual novelty.

Four LEDs are angled such that they turn fan blades into LED light pipes creating an illuminated arc while the fan spun.

A glued-on clear cover hides the LED within. Getting good leverage on this cover is tough with the fan blades in place, so I’ll work on removing the fan first.

A razor blade made quick work of the rear sticker.

Under the sticker, we can see fan motor shaft held in place by a small white plastic ring.

Remove the ring (not terribly visible against a white background, I admit) and the fan hub slides free. Despite the racket it has been making, I see no obvious signs of wear on either this fan hub shaft or the hub bearing. I guess a tiny amount of wear was enough for the system to start wobbling.

It was easy to break those LED covers free once fan blades were no longer in the way.

The blue LEDs appear to be standard 3mm diameter units, powered by wires that were glued into channels molded into fan hub support beams. Pulling them free destroyed the clear insulation on those wires. Given how affordable LEDs are now, there’s not much point trying to salvage these LEDs beyond trying to see if I could. I had a 75% success rate: one LED out of four was torn off its wires, oops.

I removed the fan hub, and it appears this chip is in charge of the operation. Marked FTC S276.2QD, a web search found this to be the FS276 two-phase DC motor control chip by FTC. The website indicates Feeling Technology Corp is a Taiwan-based semiconductor company. The chip’s datasheet shows an integrated hall effect sensor, which explains why it is positioned to pick up magnetic field of the fan rotor. It has four pins: power on one end, ground on the other, and sinks for two motor phases.

The single-sided circuit board marked ZB111228 implemented the FS276 datasheet circuit with a few additions. Around the perimeter, we have pads for the four blue LEDs, each connected to power and ground through a current-limiting resistor marked with 681. I believe this means 68 * 101 = 680 ohms. We also have a transistor, connected to one of the two motor phases, to communicate tachometer signal.

I will likely find a use for the three-conductor wire with PC cooling fan connector on one end. I might stick the blue LEDs on a future project just for laughs. The motor control circuit board will go to electronic recycle. All the clear plastic will go to landfill.

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