Hi everyone, I solved this buying a silicon cover for the heat block (as Phaedrux mentioned) you can get some pretty cheap on Ebay, I also realised that you don't need to have a E3D hotend, they are not available for every hotend, but you can found for the most common. With this the temperature only goes down 5 degrees and in a few seconds it's in the desired temperature again.
Thanks everyone!

@deckingman @burtoogle Understood now, thank you folks.

Good man @wilriker, Thanks a lot!

@Phaedrux Sorry for the late reply, I just did, and all the same. I'm not an expert but I found it wierd too, I just ordered a new Duet wifi 2 hope this time I dont screw up, but I would still like to know what's going on as I could use it in other machine (That's the idea anyway).

I don't know if this gives any bell, but I believe it's important to notice that before it stoped working my E1 was always on as soon as I applied the 24V on VIN.

Even if that says nothing to you, thank you very much for the help!

@Phaedrux Thank you very much for your reply, I have attached some photos, I forgot to metion that I never saw smoke coming out of the board.

The CPU is getting hot when I connect the board via USB.

I did everything I could in the guide, as the jumpers are not working (tested again just now). Change the USB cable was one of the first thing I did, but this cable works fine with my other Duet Wifi 2.

Hi everyone,

Before I tell you about my issue let me just do a intruduction. In last year I have been trying to devoloped a "All-in-one" machine, for now just CNC, 3D printer and laser engraver. I first did the machine working as a 3D printer and it was working perfect, I then decided to add the CNC fuction, here is where I started having issues.

I was trying to make E1 working as the signal for M3/M5 and some weeks ago this was working, my only problem was I nedeed the PWM signal from E1 to be 12V and my bord is working with 24V, this to be able to control the speed from Duet, so I added a MOSFET to reduce the voltage from 24V to 12V, for stupidity I forgot to add a pull down resistence and only noticied that after about 2h of testing. Before all of that I should let you know that I might have done a shot-circuit on E1 because my 7.5A fuse did blowned up (This was last week too). Returning to the MOSFET in this time I realised that E1 was always turned on as soon as I powerd VIN. I even removed it from the g-code and the issue as there. As Duet as a lot of Heaters I tought I did blown up the E1 output and then decided to do the exact same thing but this time using a heater controller from the pins in the expasion header. During the test the wifi stoped working, I then connected duet via USB (with VIN off) and the exact same happenned, I then realize the 3.3V led was powered off, I then did all the steps there I found in a guide to try to solve the problem, nothing worked even after removed the sd card, I decided to measure U2 to see if there was 3.3V coming on the ouput, and soon as I mesured it the 3.3V led turned ON. (Weird for me).

The actual issue: Now when I power duet wifi 2 via USB cable the 3.3V led lights up, the 5V lights up, the wifi won't turn on, the DIag led won't turn on too, with or without sd card, tried to do the erase step all files are still on the sd card and everything is the exact same thing. I don't know if it matters or not but sometimes when I plug the usb cable the endstop lights next to the steepers ligths up, and I am doing all this test with everything disconected. PC can't recognise that I pluged a USB too, so I can't send any comands to Duet. I belive something is burned I am just hopping is something I can fix without having to buy a new Duet.

Sorry for the big text.

Thank you!

@deckingman @burtoogle Understood now, thank you folks.

Hi everyone, after around 7/8 prints with my new Duet wifi board it was the first time that I actually saw the printer finishing a print and I realize that after the last layer the printer takes 5/10 minutes to execute the end code which explains why I have been getting a bit of damaged plastic in the top of every print my end code is this one:

G91 ;relative positioning
G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+0.5 E-5 X-20 Y-20 F9000 ;move Z up a bit and retract filament even more
G28 X0 Y0 ;move X/Y to min endstops, so the head is out of the way
M84 ;steppers off
M104 S0 ;extruder heater off
M140 S0 ;heated bed heater off (if you have it)
G90 ;absolute positioning

This was the one that I used in my previous board as well and It worked more than fine

Hi everyone, I solved this buying a silicon cover for the heat block (as Phaedrux mentioned) you can get some pretty cheap on Ebay, I also realised that you don't need to have a E3D hotend, they are not available for every hotend, but you can found for the most common. With this the temperature only goes down 5 degrees and in a few seconds it's in the desired temperature again.
Thanks everyone!

Good man @wilriker, Thanks a lot!

@t3p3tony @Phaedrux @deckingman Thanks for your answers guys, It still didn't work, but I manage to after the fault reset the fault (not the printer) and then heat up the hot end again with the fan on and it did work and have been now printing from 1h (Still sucks because this means that every time I want to print I have to wait until it finishes the first layer). It looks like that only happenness when it change the layer for some reason. My printer is an Anet A8 with some modifications, but I'm still using the original hotend, I was wondering maybe the resistor is too weak to handle higher temperatures?

@t3p3tony Thank you for your answer, yes I did saved, with the command M500, anyways I am now doing the alternative option, I will let you know how it went.

Hi everyone yesterday I started to print with PETG normally I only use PLA, and it was very hard for me to print the famous 3D Benchy but after about 5 tries and 1h I manage to make it work it without the message for heater fault, I realise this is happening because whenever the printer finish the first layer the cooling fan turns on and the heater goes down about 15ºc, yesterday I did the PID tuning with the fan on to see if it would solve the problem I thought it did since this morning the 3D Benchy was printed nicely, in the same morning before I went to work I started a big print, (around 12h) when I came back from work only the first layer was printed (basically when the fan turned on I got the heater fault again) how can I solve this?