Molex for Heated Bed fries (twice)  

RE: Molex for Heated Bed fries (twice)

Make that 3 times. See photo attached. I chatted with the support staff and they (Robert) simply suggested I replace the motherboard. This seems unreasonable without any other testing/insight. Does anyone here have ideas? TIA

RE: Molex for Heated Bed fries (twice)

The molex connectors come in various qualities. 

Generally the genuine Molex versions are good. The copies are not so good. 

Problems seem to occur due to poor insertion in the first place. This can be exacerbated by the spiral wrap insulation used on the first MK2 printers. And early mini Rambo boxes.  Which had cable ties instead of screwed clamps. 

The wire bundles tended to work their way out of the case and put strain on the connectors. Which lead to failure. Often people replace one side of the connector and not the other. Unfortunately overheating one part can overheat the other and make it less satisfactory and more likely to fail again.

Some people replace both sides of the connector. 

Some people bypass the connector and solder the wires directly to pads on the board. Some people fit xt60 connectors to replace the molex connectors. Some people use the. Rambo mini.output to drive a MOSFET switch which removes the high current switching off the mini Rambo. 

And others, replace the mini Rambo. 

I am still using my original mini Rambo. I was very careful to  make sure the cable strain relief fittings were tight. Following my experience with the MK1 prusa, which used ABS filament for cable bundle support.  Abs had a short flex fatigue life. And caused my power wires to break prematurely. 

So... Molex connectors can work for a long time. If they do fail once. You really need to replace both sides. 

The reason for failure may be down to strain on the wiring. Pulling on the molex connectors. 

Switching to the most recent Rambo/Einsy box. And good 3mm nylon support filament may help prevent future repeats. 

Also replacing the stiff Prusa power wires. With flexible silicone wires. May further improve functionality. 

Regards Joan

RE: Molex for Heated Bed fries (twice)

Thank you so much for the detailed reply Joan.

When you say "both" sides, I assume you mean the side soldered to the original mini Rambo Board. So, I would either need to replace the board or do some tricky soldering work it appears.

The heated bed itself seems to be alright. Could this also play a part here?

Jon

RE:

Hi Jon.

It is likely that the heatbed is fine. A short circuit heated should take out the Fuse.

Soldering 16awg wires. To the back of the connector on the board and soldering xt60 connector female to these wires with enough length to drop below the edge if the Rambo PCB.(insulate with heatshrink tube). Solder a male xt60 to the ends of the bed heater wires. And bypass the molex is possibly the easiest alternative

Regards Joan 

RE: Molex for Heated Bed fries (twice)

Just wanted to thank you Joan. I received the parts over the weekend and have soldered in the connections. All seems to be working fine for now.

Jon