Shorted circuit for hot end fan

Phaedrux

The damage isn't always visible.

You can test them with a multimeter. Be careful with the probe tips.

https://www.google.com/search?q=testing+mosfet+with+multimeter&oq=testing+mos&aqs=chrome.3.69i57j0l9.4510j0j7&sourceid=chrome&ie=UTF-8

gperman

@phaedrux digikey kept sending me the wrong components.

I resoldered in a new mosfet but that didnt change any symptoms. Took the hot fan off and tested, works good. heated the hot end up past the threshold fo rthe fan and only see 3v at the pins off the duet2 wifi board.

I replaced the mosfet at TR5 (Fan0) I believe that's the correct fan for the hotend. No effect.

I suppose I could switch the fan to pwm fan2 but that doesn't fix my board.

Phaedrux

Can you show a photo of the repair job?

gperman

@phaedrux alt text

gperman

@gperman sorry for the poor camera quality. That was the best I could do. These are very small.

gperman

@gperman i didnt touch anything but TR5

dc42

@gperman said in Shorted circuit for hot end fan:

@phaedrux Thank you!

Also, does anyone know of a wire strain relief apparatus that goes on the two main in connectors for a smart effector? The movement of the effector keeps breaking my wires art the crimp.

I tie the cables to the Bowden tube. It doesn't completely eliminate flexing, but it does reduce it.

dc42

@gperman said in Shorted circuit for hot end fan:

@phaedrux digikey kept sending me the wrong components.

I resoldered in a new mosfet but that didnt change any symptoms. Took the hot fan off and tested, works good. heated the hot end up past the threshold fo rthe fan and only see 3v at the pins off the duet2 wifi board.

I replaced the mosfet at TR5 (Fan0) I believe that's the correct fan for the hotend. No effect.

I suppose I could switch the fan to pwm fan2 but that doesn't fix my board.

Check that you still have VIN voltage on the positive output pin of the fan connector. Also measure the gate to source voltage of the mosfet. It should be 3.3V when the fan is supposed to be on, and 0V when it is supposed to be off.

gperman

@dc42 i measured the V+ Header pin on the duet2wifi board (multimeter between v+ and - ) when the fan is supposed to be on and it outputs 3.something volts. Forgot to write it down.

gperman

@dc42 performed a mosfet continuity test as per:
https://www.google.com/search?q=testing+mosfet+with+multimeter&oq=testing+mos&aqs=chrome.3.69i57j0l9.4510j0j7&sourceid=chrome&ie=UTF-8#kpvalbx=_6gCnYJmFE-yj_Qb_xKjgBg17

Realllllly difficult to get my finger in there to short out all 3 pins but i think I did......maybe.

When I short out all 3 then probe source to drain I get temporary continuity that slowly dissipates to open circuit. Then probe source to gate and get the same thing......light continuity 1900 or so that dissipates to 1.

pretty sure its a bad mosfet. Going to resolder one in and do it again I guess.....

gperman

Using that test from that link, I cant seem to turn on any of my mosfets. I tried 4 so far. Held probes to source and gate then source and drain, nothing. No continuity

gperman

yea this circuit is dead. I ripped the copper trace off the board for the source terminal.

I cant even get the hotfan to work with the fan2 circuit. I am way out of my depth here. All I've managed to print is benchies after 2 year of owning this predator. I think it's time to toss this whole thing in the trash and buy a prusa.

dc42

@gperman said in Shorted circuit for hot end fan:

yea this circuit is dead. I ripped the copper trace off the board for the source terminal.

I did that once. I repaired it by adding a fine wire between the mosfet source terminal and a nearby component that was connected to ground.

gperman

@dc42 I bought the genuine duet2 wifi board from you. can I send it back to you for repair? how much would that cost?

Phaedrux

Where are you located? May find a local option here: https://forum.duet3d.com/topic/13875/community-repairs?_=1622215254328