Bed not heating
Something weird happened to me this week-end, I have a Duet 2 wifi
I was printing, when I came to check my print for the final hour, I realised the bed was 23 instead of 60. I found strange that the machine didn't stop but I could finish my print with no issue.
I used my multimeter and realised I had no 12v at the output for the bed. I immediately thought it was a fuse. I tested all of them and they're all good. On top of that, if I remove the fuse needed for the bed, the red light doesn't come on when I ask the printer to heat the bed.
I then changed my wiring and replaced my bed by a brand new one. I still have the same behavior.
As soon as I unconnect the bed, I have 12v on the bed output. When I plug the bed back, I end up with 0v
To me it feels like hardware failure but I hope I'm wrong.
Just in case you need it, here's my config, but I haven't touched anything since a while
M308 S0 P"bedtemp" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S130 ; set temperature limit for heater 0 to 130C
M308 S1 P"e0temp" Y"thermistor" T500000 B4723 C1.196220e-7 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H0 A93.5 C632.2 D1.6 V12.5 B0 S1.00 ; Bed PID
M307 H1 A350.4 C119.1 D3.7 V12.5 B0 S1.00 ; Heater PID
Thanks so much in advance
Photo of your bed wiring?
How do the terminals for the bed heater look?
@phaedrux Hello, thanks for the fast reply !
Here's the pictures. Talking about the terminal, I can't really see anything wrong with it, however it feels a little bit wiggly. It never occured to me to look behind the board to see if something is obvious
I will report back soon, when I remove the board
So I took the board out of the machine, and the negative lead crumbled to dust.
As far as I can see, it doesn't seem to have any damaged anywhere else.
Do you think it's something a soldering iron could fix or potentially the whole trace is burnt out ?
Thanks once again for your help, I appreciate it
When and where did you purchase the board? Perhaps it's under warranty?
Spool3d, an authorised reseller in Canada
Checked out on April 25th 2020
Were you using boot lace ferrules or bare wires?
Why is there 2 wires crammed in for each of red and black?
Can you get a better photo of the back? Is the board discoloured or just a reflection?
How does the inside of the terminal look? Is anything melted?
I used ferrules, see my heatbed wiring (keep in mind what you saw before was a brand new heatbed I just received)
Wire is there two wires, I have no idea, that how the bed came to me. My guess is that they tried to save money using smaller gauge wires but two of each. My old bed wasn't like that. I can provide picture of it if required. Even the doubled wires have ferrules :
The inside of the terminal looks good in my opinion :
Unfortunately, I though it was just a reflection but now with the flash it's clearly discoloured :
Can you give us some details of the bed heater that was installed when it originally failed?
@phaedrux Yes Sir !
Here's pictures I just captured. Let me know if you need anything else
What volts, watts, amps is that heater? Does it have a brand or product sheet?
This is a stock Anet A8 bed.
The Stock heated bed is 12V 1.2Ohm i.e. 10 Amp Peak Current.
When I measure it, I get 1.1ohm so the bed is not shorted or anything.
Also it is very weird that no fuse blew up when the terminal toasted. It feels like an early failure of the terminal
Good old Anet A8.
The fuse would only blow if the bed shorted for enough time. As you say, I don't think it shorted. The overheated like that is usually caused by a loose connection at the terminal/wire causing increased resistance.
If the terminal itself looks ok you may be able to reflow the pin with a powerful enough iron.
@phaedrux Okay, I was waiting to see if there was any way to have it RMA under warranty before touching it and potentially voiding the warranty if I had one.
I will see if I can find the terminal locally and will solder it back together.
I think it will work because with no wire inside the terminal I could see 12v. I guess tightening the terminal on the wires flexed it just enough so the burnt leg wouldn't contact with the trace anymore.
Thank you so much for your help, I appreciate it
Unfortunately you're a year and a bit past purchase already.
If you're able to desolder the entire terminal and replace it I think you'll be back up and running. The ground plane there is quite large, so you'll need a powerful iron (or two smaller ones) and maybe a preheat of the area.
If that's not something you feel confident in doing yourself we may be able to work out an exchange for a refurbished unit at reduced cost subject to availability.
@phaedrux Okay thank you so much for the heads-up, my soldering iron is definitely not up to par so I will look for an other one.
I will update here once the terminal has been changed. I hope I'll be able to find an equivalent terminal locally
Thanks once again for all of your help, I really appreciate it
peter247 last edited by
@jmaxime89 OR CHEAT ?
If you have the voltage but no current fit a mos-fet to do the high power switching external ?
@peter247 thanks for the idea ! I have two mosfets laying around my workshop. I'll do that for sure, it will protect the new terminal !