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I have a Max V1 which I purchased back in late February. I moved into a new apartment at the beginning of this month and finally got around to using my printer again, but I couldn't get the layer fan to spin. I turned it on from the LCD and went poking around with a multimeter and found that the board wasn't outputting any voltage to the fans. I also tried turning on the bed and the hot end, and they worked just fine. Last time I used the printer was about a month ago, and the whole thing was working fine then. Any recommendations on diagnosing the problem further? For what it's worth, I haven't reconnected the hot end heater wires yet, but the printer gave the wires 12 volts when I set the hot end temperature, so I'm assuming that it doesn't matter.

Thanks

Check the fuses on the rambo.


with your voltmeter on the ohm setting. If you get infinity then you have blown that fuse.

I would then check the solder pads on the fan connector if they have jerked/broken. But that is very unlikely.

The fuses on the RAMBO are all still good. Interestingly, the red LED still goes on and off when I turn the fan on and off, so it would seem that the signal is getting there, it's just not switching.

I have not diddled with the rambo at all but it could be that one of the mosfets or whatever drive the output has burned.

If you only have 1 extruder, you could use the heating output for the unused one to drive your layer fan.

I think it's unlikely you blew a MOSFET, the circuit is pretty straight forwards. Though it is possible, I believe the LED is on the same power circuit as the actual MOSFET, so if it comes on and you have no power coming I from the connectors, it's likely not a fuse and something else dead.
Are you positive you have the fan wires connected the right way around, most small cooling fans will only run one way.

You could swap to the other outputs for the fan, on the older Rambos they are all identical except the bed output.

Well, I checked the terminals of the fan output with my multimeter and it read ~60 mV both on and off. The other terminals also read close to zero when the fan was set to 100%. As I mentioned in the post, I then turned on the hot end and read ~12 V off my meter, so whatever the problem is, I think it's before my wiring. Of course, I triple checked the wiring when it didn't work the first time. I also think it unlikely that the FET is blown because while I was poking around with the fan set to 100%, I felt the FET and it wasn't any warmer than the rest of the board. I'm used to FETs turning into shorts when they die, but maybe there are other failure modes I'm not familiar with.

I think for the short term I'll try using teoman's solution of just rewiring to the second extruder and running it from there.

I'm just bothered by the fact that something isn't working on a printer that I haven't even put a full roll of filament through. If I could at least figure out what isn't working, I would feel slightly better about it because I might know what to do to fix the problem, rather than fixing the symptom. If I had the bad luck of getting a lemon board, there's no telling when or how the next part might fail.

Thanks for the help.

Turns out, if the terminal block screws aren't fully tightened, they don't electrically connect to the system. So even though there may be 12 volts going where it should, one would not see it by putting multimeter probes on the screws of the terminal block. Of course, when the board is installed, the only part of the terminal that can be reached is the screws. Ultimately, the problem was a loose screw. I feel like an idiot for not checking that before, but I'm glad the solution was that simple.

What's important is that you got it fixed.
Good job in diagnosing.

Good job.

Glad it was not complicated.

If I had had the same problem as you, I would have probably run through the exact same course. But thanks t o your posts if it happens to me, it will be a shorter debugging process.

Thanks for posting the solution.