Heated bed doesn't heat anymore

just reflashed the firmware, nothing changed…

It’s better, but still 150$, do you have the reference of the board, I have to look for a resseler here in canada to avoid expensive shipping and custom fees…

I’d like to be sure that the board is the problem before order a new one…

The flashing red LED says your RAMBo is working and it is probably the wires on the RAMBo Bed connector to the heat bed itself. You can just unplug the bed heater connector from the RAMBo and measure about 2 ohms on the two wires. If you do not then you will need to find out which if not both wires are open out to the heat bed connector.

I wish it is… I’m a noob in electrical stuff, hom to set the multimeter to check ? Do I have to check when the TAZ and the heated bed are powered on ?


There is no need to have the printer powered on while doing the checks for resistance. It also can cause the readings to fail if the printer is powered on. Along with some things do not like being powered and not having something connected to them.

As for how to set the multimeter that depends on the type and functions of the multimeter you use, so I can not tell you that right now.

Ok you mean testing the heated bed. It’s not necessary, I tried another heated bed and it doesn’t work.

Not quite, if you measure the unplugged heating bed connector to the plugged in heat bed you are checking the wires between the connector that you have unplugged from the RAMBo to the bed and back to that connector. That will tell you if you have an open bed wire between the control board and the bed.

Found the problem, thanks to you !

I’ll contact lulzbot support to order the plug and the wires

I wrote to lulzbot support. they are not able to sell the bed wiring harness. :imp:

Is it normal for a one year printer to not find parts ? I mean that’s not a chinese low cost printer, it’s a 2500 box printer and it’s not normal, in my opinion, to have problems to buy parts…

Looking for IT Works 3D, but I don’t know if they ship to Canada, shipping cost, custom fees…

I am re-considering my idea to buy a TAZ 6 as second printer :unamused:

They also have problems with Mini bed wires breaking in the cable chain and are unwilling to sell replacements. Overall Lulzbot is a great company to work with but they have developed a few rough spots as they have grown into a larger company.

I have several Taz 5 machines and have had very few problems with them overall. It isn’t the norm for problems like that to happen but, they should take care of them by setting up their sales system to allow exception sales of uncommon parts.

I would be more concerned about the reason that connector was so hot. Was there a short? If so, why didn’t a fuse blow. Could you tell what caused the problem?

I’ve been having similar issues with my TAZ 5 although my heated bed still is working. Thact connector is getting too hot to touch and is smelling like magic electronic smoke. I have one more print job to finish up this evening then i am going to see what my connector looks like.

Really! I will have to check mine out as well.

Here is my photos. TAZ 5. Bed PWM set to 205. That should limit current draw to about 20 amp. Pin 2 is melted in the connector and on both sides was melted into its neighbors.

Good grief. Lulzbot has to be seeing this in the cluster.

My O-scope shows 1.7 ohms pin to pin on the male side and 2.2 at the rambo terminal.

I’d encourage everyone to power up and set their beds to something like 60 degrees science and feel the connector while it heats. You will have to de loom the wires and feel them to see if they are hot or not. On mine the connector and wires were almost immediately hot to the touch.

I had a slightly different issue that knocked my bed out last weekend. In full disclosure though I have worked on the electricals of my machine, so I may very well have caused this issue myself. The charred section was on the power leg that feeds the print bed. I notice on the newer printers (mine is electrically mostly a Taz 3) the wires have been beefed up to the next gauge up and are better quality looking copper. The heated bed cable itself seems to be fine though. I’m thinking I may have to grab some crimp pins and make a new cable anyways though.

Anyways, like I said, I’ve worked on the internals of this machine, so this is most likely not typical and is most likely user caused. But it’s a neat picture. I did pull the wire out when removing the switch, prior to that it was well attached.

I have seen a couple machines like that myself. It gets hot at the crimp joint which is where the ones I have seen are turning brown and then black. So you might solder the wires so if they do start getting hot they might melt the solder and solder themselves in the crimp. YMMV.

Good idea, I’ll give that a shot. I plan on doing some rewiring on this machine as soon as I get the second one up and running anyways to make use of my new cable hider thingies so when I get to that the bed wiring will also get done.

I looked up the parts for the bed cable itself. Digikey carries most of them, Mouser carries the rest
Housing for case and cable ends

Heated Bed pins:
https://www.digikey.com/products/en?keywords=A31997TR-ND (Anyone know the amp rating for these? they look like Molex computer PSU pins so it should be up there )

(Rated up to 25amp per pole)
Bed cable plug housing
Bed cable pins

I’m having this issue on my Taz 5 as well