Anycubic i3 Mega

Before I ask my question I will fully disclose that my knowledge of electronics is pretty limited so it might seem like a dumb question.

I have a 12V 8W laser that I got for Christmas but didn’t get around to installing it until this weekend. My wife got it based on the recommendation of a friend who runs the same one on his CR-10. The laser has a power input with an AC adapter and a separate TTL/PWM plug as well. Now, the way my friend runs his is with only the power input directly from his fan port, no ttl plug at all. The fan essentially switches the laser on and off as needed. I assumed I could do the same.

Since the i3 mega doesn’t have an empty fan port I installed a switch with the intent of swapping between the parts fan and laser as needed. After much tinkering and redoing (didn’t realize fan runs on (-) so I had switch on (+)) I got it not really working. The fan on the laser would power up but not the laser. I later read that the Fan0 is limited to 9V but I have the firmware update that is supposed to fix that. When I switched it to Fan2 it powered on. Seems like Fan0 is still at 9V.

In all of that process I’m pretty sure I crapped out the fan transistors as they are both 100% on now, regardless of what I do. Could have powered them up without a load or fried them by turning on an 8W laser. I put everything back to stock and even reflashed original firmware with no luck on fan problem. I have a new board coming in the mail. I don’t have the skills to replace the transistors.

Now my actual question. I think the power only approach wasn’t quite right. Since it has a dedicated power port, if I plug that into the wall and then plug the TTL/PWM into Fan0 will it work? Does the TTL/PWM have the same power requirements as the whole laser? The paperwork says it’s 0-5V so I’m assuming no but don’t want to screw up another motherboard. When the TTL is plugged into the fan, does that keep the laser from firing until the fan port tells it to? Out of the box when I plugged in power it fired up right away so I assumed it would do the same attached to the printer. My new hypothesis is that I would power up the printer first, which would be sending no power through Fan0. Then plug in the laser. The laser would remain off until Fan0 sent a signal to turn on.

Am I right, wrong, or somewhere in between?

Thanks

I am trying to set up the linear advance on my Mega S. My current set up includes TMC 2209s with no modifications (just pulled the old drivers switched the plugs and installed the new ones.). A Hermes / Hermera extruder ( Bowden) and a v6 hotend. Currently using Marlin 2.0.5.3.
Printing PLA / PLA+ at 206C
Bed 65
esteps 403.24
K.014
Print speed 45mm/s
retractions were set to 3mm
loading speed set to 28mm/s
unloading speed 90mm/s
although I am able to get a smooth surface on most of the print I have artifacts as follows. The dark blue benchy shows print quality without linear advance enabled.

like discussed in this thread: https://www.thingiverse.com/groups/anycubic-i3-mega/forums/general/topic:42941
after trying to print ABS at 105C bed temperature my printer failed and started showing -14C for the bed temperature.
I ordered a new bed and installed it with no success. It still shows -14C.
Main board failed?? : ( How can I test to be sure? Thanks!

i bought my mega s last years and i am not sure if i did a firmware update.

anyway.... today i noticed a Marlin_TFT_MEGA_S_V1.1.5.ino.hex firmware update on the anycubic website.

but (hell how i hate this) no release infos come with the file. :(

is there any source where i can see hat was fixed/changed?

why can companys not include a small readme with firmware updates. :(

is it recommended to flash the latest firmware with anycubic printers?
or is it better to leave it alone? are there siginificant changes in the update that makes the print(er) better?