Hello,

A friend have the same project to replace he's optoma fans with a Noctua.
He bought a PWM version of the 80mm fan with the assurance of Noctua for compatibility with 3pin connector : https://noctua.at/en/can-i-run-4-pin-pwm-fans-on-3-pin-fan-headers

Now He's optoma shutting down because he can see the fan reduce his speed so the controller finish by return the security code I guess.

He tryed to disable the eco mode (in first step to test with 10v) but same results...

Did you know if PWM fan was a bad idea and not compatible with the optoma controller ?

Bests regards

I decided that this mod was a little outside of my comfort zone so I completed a simpler version of it using fans which more closely followed the specification of the stock fans. 

Computer Cooling FanDC | 80 mm | 3-Pin | Silent

Brand: Nedis
Vendor Part Number: DCFAN8025BK

EAN number: 5412810322473

https://nedis.com/en-us/product/computer/components/desktop-assembly/550718398/computer-cooling-fan-dc-80-mm-3-pin-silent

These work without needing to add a resistor to boost the Volts. Having dabbled a bit with making silent PCs over the years I'm SURE they will be significantly noisier than the high-quality Noctua fans which the original mode used. BUT, to my ears, they are much quieter than the stock fans AND the exhaust temperatures are 15-20% lower at all brightness settings.

This is enough of a win for me. Goodluck!

I completed this mod today. The difference is amazing. You can get the fans and resistors here. https://www.amazon.com/gp/product/B00B5R6N30/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B00NEMG9K6/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

If you left your soldering tools in Alaska like I did.. then .. https://www.amazon.com/gp/product/B071VLFGXL/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

                When you take the projector apart, watch the top, there is a ribbon cable to the power switch, and a tamper switch which can be unplugged. The switch opens when you open the lamp access panel. I wanted to test it with the top off, so I shorted the tamper switch and taped the power switch parts together until I was finished. You can remove the ribbon cable if you wish, there is a small plastic cover that tips back and it will come out. Just be sure to have that open when you put it back, and press it back down. It is covered with tape from the factory.

This mod attaches a 680 ohm resister between +12vdc (Vcc) and pin 4 of two different NCT3941S fan drivers, so two small 680 ohm resistors are required, along with a steady hand on a fine point soldering tool. The components are very very small. I suggest that you use a magnifying glass, or wear two pair of reading glasses like I did…
After the mod, pin 4 of each NCT3941S measured 1.9vdc. The center point between the resistors is +12vdc source voltage. It just happens to be at that point on the board that is convenient to use. You can probably find it many places if you are nervous about spotting the resistors there. The two components at that spot are both connected on the foil side, so it doesn’t matter if they short (I did short them while soldering). It’s 12V to the 680 ohm to pin 4 on each NCT3941S. This is very tiny..
The data sheet for NCT3941S can be found here https://www.nuvoton.com/resource-files/DA00-NCT3941SA1.pdf

I cut the wires from the old fans about one inch from the fans. I did the same with the new fans and just soldered the new ones to the old wires (same colors) and insulated with heat shrink tubing. The new fans are larger than the old ones, and I used a small diagonal cutter to cut out some of the plastic. The speaker had to be repositioned or the fans would not fit. I just turned it sideways to face the fans, and used the rubber face to help dampen the fan vibration. It still sounds the same. I had to cut some of the plastic where the speaker was, to allow the fans to fit. The projector cover has two vertical stiffeners above the fans that need to be trimmed about ½ inch, the whole length.
I was going to buy a new projector for my new 135” screen, but now I will keep this one. I doubt that I could find another projector this quiet with this performance.

could you make an tutorial ?

and can you tell us the Results, is the Modded Version cooler and a bit quieter?

best regards