I’ve had that precise problem on the 11A rail, caused by too little contact between the plug and socket, so current was flowing across a small bridge, melting the plug. I solved it by sticking a toothpick into the plug, improving the contact between the plug and socket. But soon I will replace the plug and socket with a new one.
I like going for premium brand connectors where reliability is paramount. Also, I use Ferrules quite a bit to make the whole shebang a little tidier.
Welcome to the club! Yes that is a problem I am very familiar with and the biggest reason I have come up with is the terminal block solder point on the board. It gets really hot and the solder breaks reducing the surface area for heat dissipation and reduces the overall rating of the connection which makes it heat up even more eventually melting the block. The last time I had it happen I resoldered it spreading the solder further down the trace to give it more of a sink and it seems to have solved the problem.
always when i get this type of conector on ramps board I imediately replace them for this one: https://cz.rs-online.com/web/p/svorkovnice-pcb/4948928/?searchTerm=494-8928&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3439342D3839323826 - that default is for right current, but for continuos not bang-bang or pwm type of regulation and with poor contact it leads to melting after some time…
Thanks @Dalibor_Jesatko – higher quality contact is the main thing. And remember that with screw terminals you shouldn’t “tin” the ends of your wires. http://reprap.org/wiki/Wire_termination_for_screw_terminals because the contact can quickly degrade due to expansion/contraction.
The best of both worlds would be if there was a plug with really good reliable contacts - and you’d think that would be the minimum. Personally, on my i3 machine, I’m probably going to do as you suggest and replace the plug with a screw terminal, because the PSU is attached and won’t be moving for many years.
yes, it is better to use ferrules.
normaly it is better to use screw terminal
- if it is for right current, and right cable termination, then it is almost immortal
no unwanted heating caused by contact resistance of contacts inside the plug - i found, that quite often you will change arduino then ramps. accidents like shortcircuits on endstop tends to do no damage to nonpasive components on ramps more often dies voltage regulator on mega or mega itself and then i need only unplug ramps from mega and change it.
by me it is only cheaper part for chinese production. same as mosfets for heatbed…(i am speaking about ramps on aliexpress or dealextreme) i had one board that had mosfet which i can take it out after 10 minutes of bedheating (mosfet had pasive cooler)
if u use this mosfet: IRLB3813PBF u can use bed without cooler on this mosfet
PS: sorry for my english…
@Dalibor_Jesatko . Thanks for specifying a particular MOSFET. Gives me something to think about and I’m a fan of International Rectifier parts too.
I mentioned this sort of problem in issue 2 of the RepRapMagazine - Page 47 - http://reprapmagazine.com/issues/2/index.html