duet fried after crash?

Ahoy folks! I think the duet board for my Ormerod 1 died today after crashing the printer head.

I print in ABS due to PLA's tendency to warp in the hot, humid environment here in Georgia. To reach the bed temperature needed for ABS to stick, I often place a sheet of cardboard insulation on top of the bed, and remove it just before starting the print. Unfortunately I got careless and today I forgot to remove the insulation. It got through about half of the first layer before the entire thing jammed up. By the time I noticed, the printer had stopped communicating with the web interface, and a thin stream of smoke was rising from the printer head. I immediately unplugged it and raised the head enough to remove the cardboard, but the damage was done. My printer no longer responds to USB or web interface. If I plug in the power supply, both the bed and nozzle heat up without control. From what I can tell, the smoke was from the nozzle heating up too much, because I do not see any signs of burning on any of the wires or components.

Any idea what went wrong? Is the board salvageable? Or do I need a new one?

Edited 1 time(s). Last edit at 10/26/2014 12:37AM by kotori87.

From those symptoms, I think the 5V supply on your Duet board is OK but the 3.3V supply is not. Try disconnecting the proximity sensor loom at the Duet end in case the proximity sensor is shorting out the 3.3V supply.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

You may be lucky and it is a 3.3V short that has not done any serious damage as David has said, but I think it unfortunately quite possible that the overheating may have damaged some insulation and created a short between the 12V heater supply and the 3.3V to the thermistor, in which case there is likely to be irreparable damage to the Duet. I'd say the best thing to do is to unplug everything from the Duet, do not turn on the power supply and then see whether the Duet can communicate via the USB (taking its power from the US. Look at the list of available COM ports before plugging in the USB, and again after plugging in the USB. If the Duet causes any additional COM port to appear you will know it is at least running and thus probably not badly damaged (I suggest the COM port method because there is a remote possibility that the Duet has lost its firmware and so will need to be re-flashed before it will again work with Pronterface).

Dave

tried disconnecting everything, with no luck. I also checked to see if any COM ports appeared when plugged in, again with no luck. Just the same solitary red LED below the USB port. It appears that the board is beyond my ability to repair, so I ordered a replacement board that arrived today. What systems should I check prior to installing the new board, so it doesn't die to the same cause that killed the old board?

Edited 1 time(s). Last edit at 10/30/2014 10:22AM by kotori87.

Do you have a multimeter / ohmmeter?
If so, check the resistances of the extruder heater (It'll be low, but shouldn't be zero) and the thermistor - thousands of Ohms (if you like, you can heat it with a hairdryer to see it's resistance change, just don't melt your PLA components).
Test these at the duet end of the wires as this will show any faults that lie in the wiring as well as the components!

I don't have a multimeter yet, but I will soon...

Should I be concerned at all about the motors, heated bed, or the Z axis sensor?

You don't need to spend a fortune on a multimeter, even one that costs less than a tenner will see you through many years of service.

Your motors should be fine. The Z-axis can't be forced down too far as the X-axis will just lift out of the Z-axis nut on the threaded bar.

I'm assuming that your heated bed is covered with at least an aluminium heat spreader.If so, then it'll be fine. If you just have kapton tape on, or a bare heated bed, then it's possible that there will be damage - you should see some physical sign of this. You could test for resistance with a multimeter, but other than a low (not zero) value, I couldn't tell you what the values are.

The Z-axis sensor should also be fine - same reason as for the motor. Saying that, it's just two bolts that need undoing to physically check it - have a look. if there is any sign of damage let me know and I'll undo mine and tell you how to test yours.

Good luck and let us know how you get on - post your resistance readings up and we can check them for you.

The most common reason for Duet failure is miss-connecting the wiring, particularly connecting 12V to the 3.3V thermistor circuit. Check your hot end connector wiring, and check where you make the connections onto the Duet board. Typically, miss-connecting the hot end thermistor onto the 'FAN0' output, then connecting the hot end heater between the thermistor and heater pins (ie miss-registering the housings by two pins) means that the 12V goes into the thermistor circuit. I don't know what caused your initial problem - it sounds like either the electronics overheated, or there was a short though the hot end wiring.

Make sure the firmware is up to date, and the contents of the SD card also concurrent with the version of the firmware.

A sensible precaution would be to leave the heater wiring disconnected (at the Duet for the hot end, and the two IDC plugs under the bed, so the thermistors still work) and test everything else first.

Ian
RepRapPro tech support

I suggest you also check (if you have not done so already) that the aluminium heat spreader is on the bed the right way round, so that it is not shorting against either of the soldered connection pads at the front of the heated bed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
I suggest you also check (if you have not done so already) that the aluminium heat spreader is on the bed the right way round, so that it is not shorting against either of the soldered connection pads at the front of the heated bed.

Yes, that's a good one. See steps 7 and 8, here: [reprappro.com]

Ian
RepRapPro tech support

The heater element reads 3.5 ohms, and the thermister read about 65k ohms. That seems normal. I also inspected the wiring. No visible damage or bare sections. Although I still don't know what caused the original problem, at this point I am confident to install the new board and cautiously begin testing.

re: the heated bed, yes the aluminum heat spreader is installed, in the correct orientation, clear from the contacts, and with kapton tape over the heated bed contacts to prevent shorts. Remember, the printer was working fine for several weeks prior to failure. So the heater element, thermister, and heated bed were definitely connected correctly.

Are there any scorch marks or other signs of overheating on the microcontroller on the old Duet board? If so, that suggests a wiring fault caused the problem. If not, maybe the voltage regulator or some other component failed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I'll take a closer look at the board when I replace it. Today I went to a build session at a friend's house so we could do 3d printer stuff. I installed a shiny new aluminum X arm and a whole stack of other parts I'd printed before the crash, but ran out of time just as I finished re-installing the threaded rod for the Z drive. So I did not get to test the new board it may be a few more days before I can try it.

I was all set to connect the replacement Duet board today, when I noticed an important difference. While the old board had pin connectors, the new one has screw terminals. So all the connectors on my wiring harnesses are not compatible! What should I do!?
should I:
modify my wiring harnesses to fit the new board?
de-solder the screw terminals and replace them with the pin connectors from the old board?
make some kind of adapter (I don't know what yet)?

In other news, I believe I have spotted the cause of the old board failing. Now that it is removed, I can look much more closely at it, and I noticed what appear to be small scorch marks surrounding a tiny pinhole opening on the big square microchip in the middle of the board, the one with the blue sticker on it.

There should be a two row pinheader above the screw terminals. there are all the signals you need. If you feel confident to read the schematics you could try to use these pins. or you could by pin headers with longer pins like for arduino shields and screw them into the terminals to get pin headers back

If you bought your replacement board from Think3DPrint3D, they have their boards with screw terminals, while we supply boards with pins. The pictures on the Think3DPrint3D website do show this.

Can you post a picture of the failed part of your board? It sounds like L7, on the corner of the chip, has failed. This is a ferrite that protects the analogue ground from the noise from the common ground, but tends to fail when 12V shorts through the 3.3V circuit. There's an anecdotal report that mains spikes may also do this.

Ian