Help reverse engineering PWM Dimmer Flicker-less mod
Adding more info I couldn't on my first post:

I edited my tests to show you guys. Different cams but same results. First one is my friends circuit, 100% flicker free (I had to crop it cause there was sensitive content on frame):

Flicker Free Circuit

The little blackouts are just me not being able to hold the supply wires. not circuit flicks...

My Flickery Circuit

As you can see, it only stays flicker free on max power. As soon as you dim out, it starts flickering.

Both tests were powered by a regular 9V battery (not ideal, but what I had on hands).

Based on the link pointed out by jsotola, I could gather a few more infos:


Frequency is governed by the 555 astable. The capacitor between pins 2 and 6 of the 555 should be responsible for that frequency.
This calculator helps to find the right cap for the frequency I want:Calculator
Assuming my R1, R2 and C values are respectively 1K, 10K and 100nF, the output frequency should be around 680hz, which matches the links video osciloscope teste. I will try to get one and verify my circuit.
A comment by brokenmonkey on the same link gave some video related tips: 



  I know 6 kHz is a safe frequency for video but it can cause audio interference, and 20 kHz is safe for audio but maybe not all types of video. 


Following his logic, replacing C1 with a 11nf capacitor should do the trick. Still, my friends circuit have a couple of other stuff applied, as shown on the images.

My friend was also emphatic that the waveform should be square. I guess it comes from factory that way too...

Thanks again for all the help :D