Burned RAMPS power connector


Thank you very much!
I’m going to test the bed and purchase a new (better RAMPS). While I’m at it, should I put bigger wires for the bed? The one I was using were rated for 17A, I got new ones holding up to 32A


13 awg will safely carry 20 amps at 12 volts. The failure was in your plug.:wink:


So that’s something “out of my control” in a kind of way…
That’s a relief! For a second I thought I did something completely wrong.


I used a 24v + 12v for one of my dollies with a ramps.
24v for heatbed and 12v for the rest.
It burned at the heatbedside supply rail on you board.

So you heatbed draws to much energy.
if you want a really good ramps buy this one: https://orballoprinting.com/en/home/54-ramps-14-sb-.html?search_query=ramps&results=12

the ramps 1.5 is relatively good / but need some mod’s to make it really good / and it is not open source.
I am using a ramps 1.6 (closed source) for my second dolly which is ok with a mk42 which doesn’t need as much energy as the mk3 bed.

If your heatbed supports 24v buy a 24v power supply and a stepdown to 12v.
And connect the 24 rail to the heatbed side and the 12v rail (from the stepdown) on the electronic side.
(or go for full 24v -> then you need a new heater cartridge + fans AND the ramps must be able to handle it)



today I was doing some maintenance on my 3D printer, while disconnecting the power supply to the RAMPS module I saw that a pin was completed burned (see attached picture).
Frankly, that’s quite upsetting!
I built my 3D printer following Tom’s guide on Dolly and I never had any issue with it. Sometimes I had some thermal runaway errors, but they were false positives (particle fan on bed temperature sensor).
Lately I had the board shutdown when it’s too hot: adding a PC fan next to electronics solved the issue.

I know RAMPS aren’t the best available board, but I just wanted to know if that’s something that happens from time to time or I did something wrong.
Any ideas?


Moorviper is on the money (as usual). I had difficulties with a heatbed that’s resistance was out of spec (.8 ohm opposed to 1.4). It drew too much current and ruined a RAMPS. So, be sure to test your bed, too. Also, some of those plugs (and other components) aren’t rated for the current the printer is going to draw. Be careful about getting a reputable RAMPS (just what MV said).



Subtract a few tenths of an ohm for the meter, itself. Should be ok, but a little slow. If you measure it while it heats, the resistance will go up. Also, if your wire gauge is too fine, the resistance will be higher.

To recap, measure the bed at the solder points, cold, and subtract .2 to .4 ohms for the meter. You are looking for 1.4 to 1.6.

Sound like the RAMPS connector failed. Check the marking on any future connectors to see that they can handle at least 20 amps. If it isn’t labeled or is labeled for less, be wary.



Just to be sure and do not exclude anything, I saw that my bed has a resistance of 1.8 - 2.0 .
Is that ok? For what I can remember, that would lower the amps, so it’s ok. The problem is definitively in the plug, right?


Is that measured when the bed is cold or warm.?
1.8 and 2.0 sounds very high.
With that rsistance it should only draw 70-80w and all should be fine / except that the heating should last long times…


I measured it when cold.
Actually I disassembled everything from the RAMPS since I burned the connector and the spare one was faulty…
So I simply connected the multimeter to bed wires.

Heating was normal, I was able to reach 70° without issues.
Could it be the heater? What’s the expected resistance value? But again, heating times were normal (210° without problems)


Thanks everyone for this crash course on voltages and power connectors!