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Smoothieboard Large MOSFET Problems

Posted by brendanind 
Smoothieboard Large MOSFET Problems
June 23, 2020 04:35AM
Hello, I'd be grateful for any help. I have been controlling an e3d hotend with one of the large MOSFETS on the smoothieboard (fet pin 2.7, I think), and this was working exactly perfectly for a few weeks. A few days ago I also connected a heated bed to another large mosfet (2.5 maybe), and (I'm not sure if its a coincidence or that the new bed has caused this), but none of the three large mosfets work anymore. I have remapped the temperature.hotend pin line in the config file to each mosfet in turn to see if any work, and ONLY the small mosfets give out a 24v (I have shorted the jumper that connnects the large mosfet Vin with the small ones, hence small mosfets get 24v), and their lights come on. When I try to switch any other LARGE mosfets, no LEDs come on (the ones that indicate weather fet is closed) and I have 0v across them. I have tried to get a fresh config file, because I thought that it could be that I had some overwriting lines which confused the system, but no luck. What I am wondering is if this damage is to the main arm chip, or simply to the mosfets, and how can I check, and what is the likelihood of this being the case? It seems like a chip problem to me, which is baaaaddd, because MULTIPLE mosfets don't work, even ones that I have never used. I'm very confused and miffed, because I see no signs of physical damage to any part of the board, and I have never seen or smelt anything weird. I would be very grateful for any help or advice, or other troubleshooting problems. All other elements of the board work great, such as the small mosfets work properly, and can deliver PWM as normal, all axis work properly and smoothly, and all LEDS (3v2,5v,Vin, Serial, etc.) are on and working properly. Prontrface can connect just fine with the board, and I can read thermistor values find, and I can send and receive gcodes fine. I'm very confused because usually when its a problem with the main chip then things all go wrong everywhere and there is erratic behaviour, so for just one element to be wrong is strange. Its not a catastrophic failure because I can always use a general GPIO and connect an SSR, its just to lose three large mosfets is very annoying.

Thanks for any advice or help!

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