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I have a Rostock Max V2 modified with a HE280.

Two days ago, the bed quit heating. In recent weeks, I have been using higher bed temps of 110 degrees for ABS whereas previously I printed PLA at 60 degrees. A wire from a brick power supply to the Rambo board overheated. I replaced the supply wires from the brick with a heavier gauge wire and attempted to print but the bed would not heat.

The hot end heats up normally.

The LED on the bed heater does not light. I have checked the three fuses and they all show continuity. A voltmeter across the terminals that connect to the wires of the heated bed does not show any voltage.

From the SeeMeCNC knowledge base, I referred to "My Hot End / Heated Bed Does Not Heat Up". https://seemecnc.zendesk.com/hc/en-us/a ... ot-heat-up

The LED on the Rambo board below "Heat-2 Bed" does not light up. I checked the physical connections and at the end of the troubleshooting procedure, it is recommended to clear and re-install the firmware in the EEPROM.

I have re-installed the firmware and the bed still does not heat.

Can anyone recommend any further actions I should take?

Is there a schematic that I could follow to look for faulty components on the Rambo board?

If the LED under the Heat-2 block doesn't light up, you may have blown the MOSFET that drives the heated bed. Ultimachine does offer a repair service for the boards.
If you'd like to tackle it yourself, you can find schematics and board layouts here: https://reprap.org/wiki/Rambo

g.

I had the same issue, with the same setup (V2 with a HE280). Printer ran fine and I didn't touch the bed for 4 years. Today, the bed stopped working so I checked the rambo, and the rambo terminals to the bed were completely melted. Posting it here so other people have a chance to learn from my mistakes. If youre running a V2 it might be worth taking a look at the rambo board.

Heating & cooling cycles can cause the compression terminals to loosen over time. That's what cause the terminal block to cook. Checking & tightening these periodically will avoid this. A bootlace crimp connector end can help too.

g.