No Temp readings anymore

[AndreS]

Hi everyone,

I got my DuetWifi (batch 4) two weeks ago and exchanged the Duet 0.8.5 in my Kossel mini (from Think3DPrint3d) for the DuetWifi.
Went like a charm and was now printing for a week. I love it, its much quiter than the 0.8.5 and all connection headers reachable with the standard mount.
Today I switched it on, heated bed to 80 and nozzle to 140 for the auto delta calibration prior to printing.
After some minutes I did the auto calibration and in the middle of it, I got heater faults on both heaters.

17:59:21 Calibrated 6 factors using 10 points, deviation before 0.208 after 0.026
17:59:00 Error: Temperature reading fault on heater 0: open circuit
17:58:55 Error: Temperature reading fault on heater 1: open circuit
17:56:50 Connection established!
17:56:47 Page Load complete!

```I started heating with my StatusPanel.

I checked the wiring and it is ok.
For further checking I took a 100k resistor with connector and put it on the sensor terminal for the bed, and got the same fault message when trying to heat. The temperatur reading is -273 on my selfmade StatusPanel and 'error' in DWC.
I put M563 P1 H2 into config.g and the resistor on temp 1 terminal and restarted the board. This heater is normaly not in use cause i have only one extruder (on heater/temp 0)
The reading is -273 / error and if I try to heat i get the same error for heater 2.

I turned the printer several times off and on. Allways the same.

Any suggestions on this or is there something broken?

Firmware Version: 1.15b (2016-08-25)
WiFi Server Version: 1.02
Web Interface Version: 1.12
as delivered and good til now.

Andre

![](http://www.familie-schiel.de/Bilder/20160922_192822.jpg)

[dc42]

My guess is that the VSSA fuse has blown. This is a small SMT fuse labeled F1 in the vicinity of the processor. I suggest you disconnect the thermistors and check the fuse for continuity with a multimeter. If it is open circuit, then you probably have or had a short circuit between the hot end heating circuit and the thermistor, or between the bed heating circuit and the thermistor.

[AndreS]

Thanks,
I will check it after work this afternoon and report back.

Andre

[AndreS]

Your guess was right, the fuse is blown.
I connected a 5x20 fuse holder with one connector at the E0 endstop GND pin and the other at termistor E1 VSSA pin, so it is electrically at the right position. Wanted not to go without fuse, because it has blown for a reason.
Now I had temp readings again.
Bed and extruder warm up for calibration.
And again in the middle of calibration: heater fault. New fuse blown.
So further investigation. Why does this happen again?
Solution:
I installed steel springs at the down end of the diagonal rods to reduce backlash.
This spring shorts some solder points at the back of the connector PCB installed on top of the effector plate when probing at Z tower, and bang: fuse blown.
I insulated the spring and backside of the PCB, put in a new fuse and the printer is running again.
I will install an SMT fuse holder for the F1 fuse if I can source one in the right dimension. Till that happens it has to run with the external fuse.

Thanks again,
Andre

P.S.:
And thanks for your hard work on the Duet. Its a fine piece of electronic. And the firmware gets better and better.

[dc42]

I'm glad to hear that the fuse protected the Duet WiFi from damage! Over the years I've heard of a number of Duet boards burning out the processor and one other component, due we believe to shorts of this nature. That is why we added the fuse.

[bot]

This attention to detail is what keeps me in the duet camp. Thanks, David et al.

[Jan]

Hi, i have the same issue (while working on exchanging a hotend …)
My F1 measures ~100 ohm, probably this is too much.
What type is the fuse exactly?

Thanks and Regards,

Jan

[dc42]

The resistance should be no more than 5 ohms. The part number is listed on the wiki. There is also a Littlefuse part that we used on the pre-production boards and is suitable.

[X4TEC]

I've just gone and blown my fuse F1, found this info really helpful and quickly identified the fuse, thanks really helpful info.

Nozzle caught on my table glass clip, which some how caused the fuse to go. I've checked the thermistor's and they read around 80K and the Hothead its about 14Ohm and bed aroundt 5/6Ohm, so no obvious shorts. Not having much fun with this 3d printer game.

[T3P3Tony]

Check the circuit between the heatblock and the thermistor and between the heater block and the heater cartridge. The heater cartridge could have failed in a manner that makes the heater block have VIN present on it.

[X4TEC]

@T3P3Tony:

Check the circuit between the heatblock and the thermistor and between the heater block and the heater cartridge. The heater cartridge could have failed in a manner that makes the heater block have VIN present on it.

I checked my heat block, no vin, but I did see 60Ohm from heatblock to thermistor, not sure if that sounds right.

[T3P3Tony]

Hmm a circuit between the heatblock and a thermistor wire is not right. To confirm can you make sure the thermistor is not plugged into the board when you test it.

[X4TEC]

@T3P3Tony:

Hmm a circuit between the heatblock and a thermistor wire is not right. To confirm can you make sure the thermistor is not plugged into the board when you test it.

Thermistor wasn't plugged in when I tested. Just ordered a replacement fuse, but before it arrives I'll disassemble the hot end as I assume thermistor must have shorted to hot end.

[T3P3Tony]

That appears likely.

[X4TEC]

@T3P3Tony:

That appears likely.

Many thanks, thermistor shorted to hot end, I've switched to a screw in type as this is the second issue from thermistor shorts. Replacing the fuse was a fun job even with my reasonable soldering skills.

[T3P3Tony]

Great you have got to the bottom of that, and good skills on the soldering!

The cartridge type thermistors that e3d use on their hotends are much easier to mount.