MakerGear Forum

Hi all,

I am having an issue with my bed heater power supply. It is the Dell 19V supply. The light comes on when it is unplugged from the Rambo, but as soon as I plug it in the light goes out. Is anybody familiar with this problem? Could there be a bad component on the Rambo?

Thanks in advance,
Jim

Check the resistance across the bed heater wires when they're not plugged in, to make sure it's not a short on the bed heater side.

If not, then it's most likely a power transistor failure.

Another quick test is to move the bed heater to the extruder 1 heater socket, and the bed heater thermistor connector from T1 to T2 (I think they're wired by default with the extruder 0 thermistor connector on T0 and the bed heater thermistor on T1); once you do this, the software and firmware thinks your bed heater is the 2nd extruder heater. So you can go into Simplify3D or pronterface, and set the 2nd extruder temperature to, say, 50C, and see if the bed heats up properly.

If that works, then you can swap the bed heater and 2nd extruder connections in the firmware, so that the firmware and software will no longer have to be tricked into thinking that the bed heater is the 2nd extruder. Since your problem could be a bed heater short, there's not much point in telling you how to modify and re-flash the firmware until it's clear that it will solve the problem.

Thanks for the quick response.

I tried swapping the 2 connectors on the Rambo, but when I try to change the temp for tool T1 in Simplify3d, I get M104 Invalid Extruder. Is there an easy workaround for this, or does it require flashing the controller? I could always try the same thing with tool T0.

If this does work and the bed heater functions, won't I still have to have a way to plug in the Dell power supply to the board? Sorry I don't have time to go through the schematics, but it is summer and I have a 6 year old.

Thanks for your help,
Jim

M3Jim wrote:I tried swapping the 2 connectors on the Rambo, but when I try to change the temp for tool T1 in Simplify3d, I get M104 Invalid Extruder. Is there an easy workaround for this, or does it require flashing the controller? I could always try the same thing with tool T0.

Sorry my follow-up wasn't as quick as my first response.

I wasn't thinking that the firmware isn't going to support the 2nd extruder, so yes, you will need to re-flash the controller. But. . .

If this does work and the bed heater functions, won't I still have to have a way to plug in the Dell power supply to the board?

I guess I was making unwarranted assumptions. So the light goes out on the power supply brick as soon as you plug it in, regardless of the state of the controller? I was thinking that it was being pulled down by bad power transistor, but that supposes that the power transistor is turned on. That is, in this case, that the bed heat has been turned on. If it's being pulled down just by being plugged in, that sounds more like a short on the board at or close to the power connector. In which case it means a call to MakerGear support.

Check the power connector closely where it connects to the RAMBo. The 19V/12V split supply has been known to end up with a melted connector on occasion. Usually this results in an open circuit, but I would suppose that a short circuit is also possible.

Thanks for your help Tim. It turns out it was operator error. We moved recently and I had to reconnect the power supply to the connector. I put the wires in backward. After reversing the wires, all is working.

Thanks for your help,
Jim