Ormerod 2 Heated Bed not Working

The negative heated bed connector on my duet board had completely burnt out, so I removed the connector (which was like a cinder on the negative side) and soldered in a piece of wire in place of the connector both on the negative and plus, however it is still not turning on.

I realise it might be the mosfet, where is it located please or is it more likely to be a problem with the track.

Not sure if it is the later Duet board (0.8.5) the Printer has Ormerod 2 528.3 on the front of the power supply.

Any help much appreciated.


Brian

The mosfet is unlikely to have burned out. Does the bed heater led on the Duet light up? What about the one on the 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].

Hi Dc42.
Yes the LED on the Duet does light up when I switch on the bed but not the LED on the bed itself.

Brian

I have put a meter across the positive bed output and the negative terminal where the 12 volt goes to the bed but no reading with the bed on.


Brian

Quote
Europa
I have put a meter across the positive bed output and the negative terminal where the 12 volt goes to the bed but no reading with the bed on.

That's odd, because the bed heater LED + series resistor on the Duet is wired directly across the output.

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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].

That is interesting, do you think that indicates that it is a track problem.

As it is a double sided board do you happen to know which is on the top and bottom with respect to positive and negative.

Very baffling!

Regards,


Brian

The only track that would cause that problem is the one on the top of the board, right at the edge, between Vin+ and bed heater +. That trace has been known to burn out on the Duet 0.6 if you use a bed heater with an unusually low resistance. If it does burn out, then there will be no power to the on-board +5V regulator either - but as you have an Ormerod 2, you won;t be using it.

So I suggest you look for signs of that track burning out, and measure the resistance between the bed heater + terminal and the Vin + terminal. If it appears to be open circuit, you can link those two terminals on the underside of the board using a piece of thick insulated copper wire.

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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].

Thank you Dc42, your advice led me to look for the fault in the right place.

It was the solder joint on the upper track of the positive terminal, now fixed and working a treat.
I brought both positive and negative out to two terminal posts mounted on the cover panel so that I can keep an eye on them in future.

And of course it now heats up much quicker as the joints are good!


Thank you for your help.

Much appreciated.


Brian