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I had to replace a fan on one of the Extruders, during the replacement process the fan was wired backwards to the old fan. I switched the leads but now my touch screen doesn't work and when the machine starts no sound is played and nothing seems to work. I replaced the fuse in the power supply and still nothing. Any ideas on what is wrong.
please help
This is only a guess but not good news. Did you have the Dreamer on when you were correcting the fan wiring? If so, I am afraid that you probably shorted the red and black fan wires together. This would have blown the FET on the driver board that controls the fan. Take the bottom cover off and inspect the driver board near the A and B Stepper drives Look specifically at the small FETs that control the extruder fans (I believe Q202 and Q205)/ If one of them shows signs of excess heat, you have found the beginning of your problem.
If the processor had the FET turned on (and possibly even if it did not), there is a chance (actually a likelihood) that the main core board is also damaged.
The fan red lead is connected directly to 24V and the black lead goes to the FET which switches it to ground. A shorted fan will cause a massive surge of current (only limited by the power supply over current protection) that will blow the FET. Some failures of the FET also result in the 24volts being applied to the gate of the FET which is directly connected to one of the output pins on the microprocessor. The microprocessor IO pins can only handle a few volts.
If this is your situation, you need a new driver board and a new core board. It might be possible to replace the components on the boards if there is no damage to traces or the ribbon cable, however, the microprocessor is not open source so you would have trouble getting the correct bootloader installed so that you could install the firmware on a replacement chip.
I hope that you find a less serious cause but I think the above scenario is most likely.
Graham
Graham, thank you for the response. I am replacing the core board after talking to Flashforge that is what they came up with.
I've just done almost exactly the same thing... shorted out my AUX fan while the printer was on...
Black screen, no response to USB connection...
Where did you get your replacement CoreBoard, and did it fix your problem?
Feeling mighty dumb right now... but expensive lesson learnt...