I've just printed my first benchy which turned out well except that despite setting up the IR sensor with the piece of belt as instructed the bed is a bit too high so first layer or two are too thin. It was done with hot end #1 on a hybrid Titan dual. The odd thing was that hot end #0 also heated up although I didn't tell it to. If I tell it to heat up on its own nothing happens and I eventually get a heat up fail message. The heater obviously words and so does the sensor. Bad Rumba board?
Are you saying that both heaters is set to exact same temp? Where are you setting the temp? In S3D, OctoPrint or on the printer it self? GCODE file if you have? Photo of RUMBA wiring?
I set the temperature (and ran the benchy code) on the printer although I did also set the temperature via OctoPrint with the same result. I only selected a temperature for Nozzle 2 but both heated up. If I set a temperature for Nozzle 1 nothing heats up and I eventually get a failure message. The temperature of #1 tracks that of #2 but with an offset. It as though power is being fed to both heaters from the one output and the temperature is being controlled by the temperature sensor on #2. The print using Nozzle 2 was fine. A solder bridge between the two would explain it except that I would expect the same to happen if I tried to set a temperature from #1 unless the output of #2 has fried #1. You may notice that the hot end fans are both wired into the screw socket. There appears to be a dry joint on the molex connector. The fan would only come on if I pushed down on the connector. To be honest I'm not getting a good feeling about the quality of the Rumba board.
Funky! I'm out of ideas and agree with you this sounds like a RUMBA issue unless you somehow got a non dual firmware or a badly misconfigured one.
Can't see how a non-dual version would be showing 2 nozzles. I'm going to try installing the latest firmware just in case that's the problem. I can see LEDs on each channel in the photo. Had it switched off when taking it. They may offer a clue. BTW I was in your part of the world three weeks ago. Oslo, Balestrand and Bergen. Beautiful country.
Got it. Loose connection on the cable between the nozzle 1 temp sensor amplifier board and the Rumba. The nozzle wasn't really getting hot. Under those conditions the input to the Rumba shouldn't float though but be pulled to zero. That connector is somewhat hidden by all the other cables. I don't like these connectors. No keyways and no locks.
Weather wasn't bad. Some cloud. Rained briefly once. Normal, I suspect! My BigBox was waiting for me when we got home. OK, 1500 components were waiting! Up and running now.