Heated Bed Connector - Burned Crispy :o(  

Re: Heated Bed Connector - Burned Crispy :o(

Did you order the kit or fully assembled?

In researching this it seems like it a design flaw of the Rambo mini controller board, but only in my opinion.

The design flaw is that if the connectors become loose then current does have enough of an electrical path and so the connectors heat and melt. I think the Rambo mini should have 2 connector for the supplied for the heater bed, but over all the Rambo design is very nice.

Re: Heated Bed Connector - Burned Crispy :o(

Did you order the kit or fully assembled?

In researching this it seems like it a design flaw of the Rambo mini controller board, but only in my opinion.

The design flaw is that if the connectors become loose then current does have enough of an electrical path and so the connectors heat and melt. I think the Rambo mini should have 2 connector for the supplied for the heater bed, but over all the Rambo design is very nice.

I bought the kit, but the website states parts are under warranty so fingers crossed. Still haven't heard back from support

Re: Heated Bed Connector - Burned Crispy :o(

The bed heater connector on my printer did not melt, but did fail.

Bed heating became intermittent. I traced it to that connector.
I noticed that on one of the sides it looked like the female pin in the connector was bent and probably not making good contact.

I replaced the original black connector with one I had from an old RAMPS I had laying around unused.
The replacement solved the problem.

This connector is a standard part.
I suggest you'd get much faster and easier resolution to take the melted one to a good electronics shop and tell them you need a replacement. Yours is pretty melted, but there's probably enought left for easy identification. It should not cost more than a few dollars.

Re: Heated Bed Connector - Burned Crispy :o(

Had the same problem with ma 12V Makergear M2, these connectors won't survive the high currents forever.
I also had the same problem with the power supply connector on the rambo board of the Makergear.

I removed the connectors, added wiring directly to the board and now use 4mm gold connectors for the heated bed and for the heated bed power supply.

After seeing this I will probably do the same before even assembling my Prusa i3 MK2.

Also, one you had a meltdown it's nearly impossible to get the contacts clean on the board and you will have another meltdown again pretty soon....

Re: Heated Bed Connector - Burned Crispy :o(

I had this happen on one of my mark 1's and learned my lesson 🙂

9 times out of 10 its due to inadequate strain relief on the cables during the build. Without the proper strain relief, the movement of the bed eventually loosens the cable slightly causing resistance, and ending up with a burnt connector like that.

Did you wire up and ziptie all the cables running into the rambo board exactly how the manual describe them?

one solution to get you back up and printing again is to remove the burn connector and solder the heated bed leads to the pads on the back of the rambo, (this will obviously require some modification of the housing ) ( I did this with my Mk1)

Re: Heated Bed Connector - Burned Crispy :o(

I *just* had the exact same thing happen after printing one full spool of PLA and about another 20 hrs printing with ABS. I haven't contacted support about this yet, but will be shortly. Seems like a dangerous flaw that may not show up until something really bad happens, it would be nice if the bright group at Prusa Research could address it, those little friction clips going to the pin connections on the Rambo being used for the 2 highest current components do seem to be a weak link in an otherwise great machine.

Re: Heated Bed Connector - Burned Crispy :o(

Mine did the same thing just this week. I just posted about it as I am wondering how long it takes support to get back to me. I had mine built for only a few days before it happened.

Re: Heated Bed Connector - Burned Crispy :o(

I had started a post thinking my connector was coming loose, but because of this post I decided to check it out and upon looking at the connector I am having the same issue. I have emailed support and let them know about my issue.

Re: Heated Bed Connector - Burned Crispy :o(

Is the connector burning from small arching from pin to socket?
Is it a size issue or simply working its way loose?
Would it be advise to secure this in some fission with maybe a non conductive silicone on the outside of the socket?

Seems if the connector is making enough contact then the solution would be to fashion some way to secure it is some non permanent way.

Re: Heated Bed Connector - Burned Crispy :o(

I think I am going to try changing both the source and output connections to a threaded post type connection, then just solder ring terminals onto the wires. Maybe even get fancy and have +'ve larger to help with orientation.

Re: Heated Bed Connector - Burned Crispy :o(

Chad

Be very careful when removing the sockets from the motherboard, otherwise you may end up with having to buy a new RAMBo.

Usually I would advise simply soldering the wires to the underside of the board and leaving the connectors in place.

Peter

Re: Heated Bed Connector - Burned Crispy :o(

Hi Peter, Here is one for you. I dont have a crispy connector but after removing the heat bed in order to change the PEI sheet the heat bed will not heat up??? I have checked the connectors, took the plug off the wire - all OK checked all fuses and then switched on and tested for power to the pins in the Rambo board. Nothing. Did the self test and noticed that when checking the heat bed the LED on the plug did come on and the report came out "All OK"

Any ideas what else I can do to get power to the bed to heat it up.

Eddie South Africa

Re: Heated Bed Connector - Burned Crispy :o(

Eddie

Occasionally beds are shipped with the cables in the connector the wrong way around which causes the LED not to light. And there have also been reports that the LEDs and/or resistors are not very well soldered onto the heater beds, again with the same effect.

Basically, the self-test is telling you that the heater is working. Pre-heat for PLA and check the bed temp on the LCD to confirm it is heating.

But first, please ensure that the heater plug is firmly home in the RAMBo connector. The fuse for the heater is the 15Amp fuse, and that needs to be checked for continuity with a DMM; you cannot always tell with a visual check.

Peter

Re: Heated Bed Connector - Burned Crispy :o(

Thanks for coming back to me Peter. Well I assembled this from a kit and for a couple of months all was well. The LED's used to flicker quite nicely and I have printed all of the models that come with the kit. My only problem had been with the Z calibration which is not explained very nicely in the manual and so I gouged my PEI sheet quite badly hence the need to change it.
If the LED's flicker when doing the self test it shows that power is getting there sometime so that flummoxed me. All fuses are OK that is 2x5 and 1x15 all checked with a multi-meter. Really frustrating. Oh well I will flash it up again and fiddle some more to see if I can get the bloody thing to work.
With regard to the reading on the LCD very strange!! the temp readout on top (the nozzle) said 215/215 while the read out under that (bed) said 89/55! Something wrong here not so
Appreciate you coming back to me. Thank you
Eddie

Re: Heated Bed Connector - Burned Crispy :o(

Eddie

Check the bed thermistor connector on the RAMBo. It may be a tad loose and be providing intermittent readings.

Peter

Re: Heated Bed Connector - Burned Crispy :o(

Eddie

Also make sure you plugged the thermistor into the correct spot on the RAMBo. It will pass the self test and show the same symptoms you are experiencing.

Re: Heated Bed Connector - Burned Crispy :o(

Maybe there is an other problem. Is it possible the connector can't handle the current?
I am receiving my printer Thuesday so I can't check it by myself at this moment.
I can't find the current consumed by the heated bed but I saw someone mention the resistance of the board is aprox. 1 ohm.
So with a powersupply of 12V that will give a current around 12A.

I found in the BOM of the Rambo mini the following connector is used at the board: 0395311004 from Molex ( http://www.molex.com/pdm_docs/ps/PS-39500-001-001.pdf ) Here is says the connector is rated at a current of 18A.

But, is the part on the cable also from Molex?
The situation is, most of these connectors can handle maximum 12A ( https://www.phoenixcontact.com/online/portal/gb?uri=pxc-oc-itemdetail:pid=1754481&library=gben&pcck=P&tab=1 ) (BTW: Phoenix also the original founder of these connectors)
So if the cable part of the connector is from an other brand this can give problems.

Maybe someone can check if there is somewhere a brand marking on the connector?

Re: Heated Bed Connector - Burned Crispy :o(

Yes, both the plug and socket are Molex and yes, they can pass 18 Amps without issue.

The problem occurs because of other issues, such as poor cable management or connection not properly made. However, the problem can also occur apparently for no reason whatsoever and has been present since the Mk1 was released, well over a year ago.

It has also happened to me after using the Mk1 for 9 months. And when it happened to me there was a reason (mentioned above) despite the fact I was well aware of the potential issue, I was simply careless.

Peter

Re: Heated Bed Connector - Burned Crispy :o(

Mine did the same thing just this week. I just posted about it as I am wondering how long it takes support to get back to me. I had mine built for only a few days before it happened.

Mine burnt exactly the same way..

Is replacing it enough or does the connector on the RAMBO also needs to be replaced?? (that one pin looks affected)