Lost heat on extruder.

After a number of months of very little activity, my poor old Omerod 1 has been pressed into hard service making face shields I have been donating to local doctors surgeries and care homes, after producing almost 150 shields, and with demand for many more, my Ormerod has stopped heating the extruder.
Temperature reading appears to be correct and on the thermistor I have around 80k Ohm. On the E0_HEATER terminals I'm only getting 1.5v when the heater should be on.
Any help to fix this would be greatly appreciated.

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RS Ormerod #472

I should add, I am using a DC42 hot end board, but I'm not sure that would have any bearing on the issue.

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RS Ormerod #472

Can anyone point me in a direction that I can try to fix this?

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RS Ormerod #472

Hi Tim,

Sorry for late reply!

Congratulations on getting your 150 masks done!

I seem to remember that the original Duet pcb /PSU combination was quite noisy( lots of high level spikes,) so maybe the Mosfet used to turn on the heater has failed under the trress. I know there is a schematic and a layout of the Duet PCB somewhere. This I think is it:

[github.com]

If not have a look around:

[github.com]

Requires Kicad ( and you may need an old version) [kicad-pcb.org]

regards
Andy Little

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

It's unlikely that the mosfet has failed unless there has been a short circuit. Most likely it's a bad crimp connection or a failed connector. Unplug both ends of the heater wires in the hot end cable, also the heater where it plugs into the hot end board, and look for signs of burning or bad connections.

Edited 1 time(s). Last edit at 05/03/2020 12:32PM by dc42.

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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].