short circuit upper fan

Hey there,

I have produced my own problem on my M200 and hope, that somebody can give me an advice to solve it.

I had to replace the upper fan on my M200, because the old one was not working anymore. No problem so far. I cut the wires near the plug and soldered the new ones. While doing this a small amount of solder must have dripped into the connector, but i didnt noticed this in this moment. So I produced a short circuit, when I started the printer. I immediately shut it off when I recognized it and searched for the reason. I removed the solder when I found it and put everything back in place.

The fan is working, but it spins faster than ever before. So I measured the voltage and recognized that I now have 24V at the fan connector for the upper fan. Afaik there should be around 12V or less.

It seems I have damaged or connected something on the mainboard by mistake. :)

Are there experienced users who can tell which restrictor, capacitor, connection or whatever I can measure to find the error.

Thank you and best regards,

Oliver

It was discussed here before that Zortrax (for whatever reason) decided it would be a wise idea to control a 12V brushless fan with a 24V PWM with roughly 50% duty cycle at maximum.

So the 24V are not unusual as long as they are not permanently there but only with duty cycle about to  ~50%. If this was a good design decision is another question though.

Ah ok, that´s new to me.

At the moment it seems, that the 24V are there all the time. The fan is spinning and making noise like crazy. :wacko:

Is there a possibility to "re-adjust" the voltage? I don´t want to replace the mainboard for that reason, but I think the fan will not last long in the current situation.

Thank you so far for your reply.

Well, a transistor can die in a way where its interior melts and creates a permanent current flow. It's not the typical scenario but it happens.

So if you measure a permanent 24V on one fan connector and permanent 0V on the other connector, this is probably what you're facing.

Note that it was discussed in another thread that transistor that drives the fan is a common N-channel FET (like 2N7002).

Someone with a bit soldering experience should be able to replace it.

You’re awesome! I guess I found what I needed to know in the other thread. Will check the transistors and replace them if needed!

Olli

It was discussed here before that Zortrax (for whatever reason) decided it would be a wise idea to control a 12V brushless fan with a 24V PWM with roughly 50% duty cycle at maximum.

So the 24V are not unusual as long as they are not permanently there but only with duty cycle about to  ~50%. If this was a good design decision is another question though.

Well, that is the case for the upper fan, but unfortunately not for the lower one (AFAIK same fan).

If you set Fan Speed in ZSuite at 100%, PWM on-time is about 99.7%, see added screenshot of my measurement (ZSuite v1.7.1).

It seems that the transistor q12 is shorted as deadbeef said. Even if the printer is off, source and gate are shorted with drain. So I’m going to replace this.

I was able to fix the problem by changing the transistor and one resistor. Everything is running again as it should.

Thanks deadbeef, especially for the link to the other thread.