Originally, the Weedo Tina2 3D printer doesn't have a dedicated fan for printed part cooling purpose.
Instead it's using a single "one and only" fan for both cooling the hotend and the printed part.
It's working quiet well for PLA prints (and especially well when using my part cooling mod), but it will become a problem when I will print with ABS.
Which is something I'm planning to do as soon as I will have my heated bed hack working as expected.
Therefore I needed to find a way to have a dedicated part cooling fan...

I already reused nearly all the free unused pins available on the motherboard (including the ISP for my LEDs) except one : the Y max endswitch pin.
But this pin is an input pin. So I had to modify my hacked firmware to be able to use it as and output and deliver 5V PWM out of it.
The Marlin firmware offers such a possibilty by redefining the pin as an second fan pin and then control it by Gcode commands just like on any 3D printer.

Before to design a tiny fan holder and blower I made sure it could work by sending M106 P1 Gcode via Pronterface to my beloved Tina2 and it worked fine.
I also adapted Cura to use the fan number 1 intead of fan number zero for part cooling (see the "Extruder tab").

I then designed a part that will hold a 5V tiny fan (20x20x6mm) and orient the air flow at the tip of the nozzle :

Weedo Tina2 Fan holder, Feb 2022

I can now control this dedicated fan by Gcode and use the original "one and only" fan to just cool down the extruder (always on - not Gcode controled).
But I must make sure it won't blow anymore air directed to the print bed. So I designed a second part that extract the air at the back of the printer instead :

Weedo Tina2 Air extract, Feb 2022

When I installed my new printed parts I noticed that the small original plastic funnel had suffered from heat.
So I added a small piece of silicone to prevent it getting worse (a small piece of cork could be another option).
I strongly suggest you to do the same before it gets completely damaged !

Having several Tina2 3D printers, I also noticed some of them have shorter screws than others for the fan (either 30 or 35mm).
Hopefully you have the longest one !  Unless you won't be able to screw the 2 bottom screws back (especially if you add a similar part as mine for the second fan - see below).

Weedo Tina2 Blower damage, Feb 2022Weedo Tina2 Blower damage, Feb 2022

Then I installed my air extract part for the original fan :

Weedo Tina2 Air extract, Feb 2022

And finally my new additional Gcode controlled fan :

Weedo Tina2 Additional fan, Feb 2022

I should soon be able to print with any filament type including ABS when I will have received my ordered parts for my heated bed hack (which you can see on the photos - work in progress).