Heated bed stopped working

[jesse]

The two small fuses on the RAMBo have contiguity.

The red light on the heated bed isn't turning on and the bed does not get hot.

The heated bed port on the RAMBo got so hot it melted the plastic connectors. The wires were also hot while I was using it.

Anyone have suggestions for fixing / preventing this problem in the future?

[edward]

If a connector on the RAMBo melted then you likely had a short somewhere. The hot wires indicate there was current, so I would check the connections on your Onyx for the short there. If it wasn't heating and the wires were hot, current was bypassing the resistance-heating path somehow.

For the red light...LEDs are polarized (that is, one side is positive and the other is negative). They won't work if installed backwards. Are you sure that it is installed correctly?

Be very careful when inserting bare wires into a screw terminal that you don't have any stray strands sticking out that might make contact with adjacent terminals. Also, all terminal screws should be tight enough that you cannot pull the wires out of the strip.

My best suggestion is to triple-check all connections before applying power to ANYTHING. It might not be the answer you're looking for, but you can't be too careful when checking electrical connections.

[jesse]

I checked the pins on the RAMBo. There's no voltage coming from the black bed heater connector's pins.

The board works when I use a different power supply.

Is there anything to reset or change out to fix the heated bed port?

[edward]

I don't have a RAMBo so I can't answer questions specific to its configuration.

Your power supply statement is confusing...what is different about it?

[jesse]

I don't have a RAMBo so I can't answer questions specific to its configuration.

Your power supply statement is confusing...what is different about it?

The power supply is a simple bench power supply. I hooked it up directly to the heated bed without using the RAMBo to see if the board would power up. It did so the RAMBo has the problem.

[edward]

Ok. Well that's not how I understood your statement about using a different power supply. I could only assume that you meant the RAMBO when you said board.

This clarification clearly points to a wiring issue, or possible defect, with the RAMBo.

[626Pilot]

Same thing happened to me. I ended up fixing it by using a Dremel tool and a drill bit to clean all the melted plastic off the pins on the RAMBo. I also had to replace the male plug, which had melted and turned into a weird shape.

[jesse]

The extruder heater also stopped working today. It was working before I took the hot end apart to replace the thermistor.

Does anyone have an arduino program that can be used to test the hotend and heated bed port?

I'm hoping that I don't need to order a replacement RAMBo. Is it possible to switch the firmware to try extruder1 instead of extruder0?

[626Pilot]

Do the red LEDs turn on when you turn on the extruder heat? If they do, very carefully test for 12V across the connector pins. If there is no voltage, remove the fuses and test them again. (Don't test them while they're in the sockets.)

[jesse]

The red LEDs don't turn on for the RAMBo or for the heated bed. The pins don't have any voltage when the heaters are turned on. The thermistors and fan0 still work.

Thinking of sending it to SeeMeCNC for testing and possible replacement. The fuses have continuity when tested off the board using a multimeter.

[626Pilot]

That sounds like one of the MOSFETs is hosed. There's also either an auto-resetting fuse (tall, flat, tan thing near the six-pin power connector) or an automotive fuse (same place) depending on how new the board is. If something's wrong with that, it could explain things. I don't remember what it does, though.

In the meantime, print some PLA... it likes no bed heat as long as you've got Kapton and some hairspray.