I am having issue with my heat bed and I am pretty sure it is something to do with firmware. I am running Marlin 2.0 firmware on an arduino Mega 2560 with a Ramp 1.4, with two hotends and a heated bed.

Both hotends work, but my issue is that the heated bed never turns on. I know it is not the bed because I swapped cables from hotbed pins - D8 to Extruder 2 pins - D9. If I turn on extruder 2 in repetier, the heat bed starts warming up.

No matter what I do, I cannot get anything from D8. If I take a multimeter to it, I see no voltage. If I do the same to the extruder pins, I see voltage. (when extruders are on)

Anyone have any ideas? is there something I am missing in configuration?

Edited 1 time(s). Last edit at 10/17/2020 07:01PM by Xgamer911.

I would start by checking if the Hotbed works, Measure the resistance of the Hotbed using a multi-meter.
This does not have to be a fancy multi-meter you will be checking for a really low resistance between 1 - 10 ohms.

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Computer Programmer / Electronics Technician

The hot bed works. As a test I swapped it from the D8 to D9 Pin and turned on the extruder. The hotbed will warm up just fine. When I attempt to turn on the hotbed, the D8 pin should have voltage going but I get nothing.

On the ramps the heated bed is on its own power supply.

The power plug has a 5amp and a 11amp side. the 11amp side is exclusively for the heated bed.

Make sure the 11amp side has power. (with a multi meter check across the gnd and + pin of the 11amp power plugs for 12v, also check for 12v between power supply gnd pin and D8 + pin)
These should always have power when power supply is on.

If you have power then the only possibility is dead mosfet or io pin on the mega.

Edited 1 time(s). Last edit at 10/17/2020 10:42PM by Dust.