I was just about to start to print out a new enclosure, then I heard a weird sound and I smelled THAT smell. I've been printing out a lot of different stuff, and suddenly this happens:

The powersupply is a modified 500w, or so, ATX power. The connection goes into a RAMP1.4.

Now I need to go over all cabling.

Any idea why this suddenly happen?

 

A little bit of resistance multiplies heat quickly if you give it enough current.
I've seen these dozens of times, usually on water heaters running in a hot environment at 18 amps or compressors with a 75 amp start current.
Spade connectors are pretty bad because of the small contact area and sometimes a poor crimp. That's why I solder crimp connectors, followed by a huge Thread about why that's the wrong thing to do.

 

For now, it's no big deal. I got more powersupplies to test, and I actually got another RAMP1.4 laying around somewhere.

Oh, well... This was not my plan this Saturday!

 

The fact that that has burned next to the connector, where it is free air and cooler that where it is cabled tied to other wires suggests the explanation is most likely a loos or dirty screw terminal.

Of course it could be loads of other stuff, including but not limited to supply and or control problems but if general overture was to blame there would probably evidence of other hot stuff and it would have been smelling warm for a while.

I assume the RAMP4.1 you refer to is some sort of power controller, probably PWM, and yiur supply is capable of driving much more current than you need.

As was previously suggested a small thermal issue can quickly become a large one if the response to a volt drop over a poor joint is to raise the voltage to compensate...
Power is I^2R and although PWM is not altering the voltage of the supply to change the current, I, average I, is a function of its duty cycle none the less. The point is a little resistance makes a lot of heat quickly at high currents and that heet makes more resistance... Blah Blah...

Check the simple stuff first, you may be pleasantly surprised to find all is well apart from some isolated thermal damage.

 

I've cut off the brunt end, and put it all together again, with some better connections here and there.

The RAMP is connected to my Arduino MEGA and is the steppermotor controller for my 3D printer. A Raspberry Pi controls the Arduino.

It does not smell burnt now, and it is printing as it should.

 

That's why I solder crimp connectors, followed by a huge Thread about why that's the wrong thing to do.

Since that debate I have ben paying more attention to stuff as I strip it for parts or repair things and to be honest soldered crimps are everywhere on older stuff.

At this point, I am more convinced that the going away from it had more to do with manufacturing costs than it did reliability/durability. I have yet to ever find a soldered crimp end termination that ever failed.

I have also noticed that on everything older those types of terminations are all made of much heavier gauge materials than what is used anywhere in today's end termination components intended to handle similar working conditions.

I fond that almost all of them are solid copper brass or tinned copper or brass and not like most of today's stuff that's just a tin or copper clad steel.