Duet aborted print due to heatbed heating failure
Posted by Brummie
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Re: Duet aborted print due to heatbed heating failure January 11, 2019 12:23AM |
Thank you both for your fast reply!
On powering board on, no voltage on heatbed pins.
Then I connected WebIF and turned heatbed on.
Stil no voltage on heatbed pins.
I checked with DC and AC settings.
by the way: it does not smell like rotten electronics
The ID-Part of the board is this:
Rest of the board seems to work as expected.
Errormessage was about 15° mismatch or so.
I found Heater3-Heater7 on expansion slot. I suppose, those pins are connected to the atmel chip directly.
I have a Fotek ssr-25 dd, which works from 3V on.
Can I connect that ssr directly to the expansion slot, or do I need some protection parts?
Edited 2 time(s). Last edit at 01/11/2019 12:54AM by Brummie.
OK, i checked:Quote
You seem to have a multimeter, so just check that you're getting voltage on the bed pin.
On powering board on, no voltage on heatbed pins.
Then I connected WebIF and turned heatbed on.
Stil no voltage on heatbed pins.
I checked with DC and AC settings.
by the way: it does not smell like rotten electronics
I very hope, that I have a genuine Duet. I paid the price for a genuine board.Quote
It's almost unheard of for the bed heater MOSFET on a genuine Duet to fail.
The ID-Part of the board is this:
Rest of the board seems to work as expected.
I did run heater tuning for both heatbed and hotend.Quote
This can happen if you didn't run heater tuning.
Errormessage was about 15° mismatch or so.
Ok, thanks for the hint.Quote
There are several such on the expansion header
I found Heater3-Heater7 on expansion slot. I suppose, those pins are connected to the atmel chip directly.
I have a Fotek ssr-25 dd, which works from 3V on.
Can I connect that ssr directly to the expansion slot, or do I need some protection parts?
Edited 2 time(s). Last edit at 01/11/2019 12:54AM by Brummie.
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Re: Duet aborted print due to heatbed heating failure January 11, 2019 01:28AM |
I extracted the board to make some photos from the mosfet.
Upside looks quite usual:
but bottom-side shows a "dirty" area. Looks and feels greasy
Heatbed was heavy used lately. I printed about 4kg ASA with 105°C nominal on a modified Ender-3. It's heatbed is not that powerfull, so that it consumed lots of power and for so stressed the mosfet.
Upside looks quite usual:
but bottom-side shows a "dirty" area. Looks and feels greasy
Heatbed was heavy used lately. I printed about 4kg ASA with 105°C nominal on a modified Ender-3. It's heatbed is not that powerfull, so that it consumed lots of power and for so stressed the mosfet.
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Re: Duet aborted print due to heatbed heating failure January 12, 2019 02:35AM |
Nature doesn't care about things, that should happen, or things that should not happen ...
When I was told to measure voltage of heatbed output, I measured impedance of heatbed to ensure, that there's no problem on the other side. Impedance of the heatbed was about 4 Ohm, which to me sounded somewhat reasonable, so I didn't grab deeper.
When I read, that the mosfet should be ok, I remembered, that my multimeter is a cheap one which is not capable of true rms ...
... but, I remembered, that I have a very tiny DSO.
So I powered the board by a laboratory power supply and connected one dso-channel to positive heatbed output and the other channel to the negative heatbed output channel.
I was very surprised, that the board consumed only about 90-100mA
(shown by the laboratory power supply)
This is the heatbed output in idle state:
When I turn heatbed heater on, the pwm-line turns into a straight line.
I have no idea, why the multimeter was not capable to measure any voltage.
Then I dismounted the heatbed. On Ender-3 the cable at the heatbed connector is supported by a plastic cable holder, which should prevent cable from breaking from the solder pad.
Well, the cabel was broken and in the endposition of the heatbed the broken cable touched the heater pad. That way I could measure an impedance.
After resoldering the cable I measured the impedance of the heatbed again and it showed 3 Ohm.
Not that far from previous result.
conclusion (for me): you can't even know without having checked every possible cause.
Thank you for your support!
When I was told to measure voltage of heatbed output, I measured impedance of heatbed to ensure, that there's no problem on the other side. Impedance of the heatbed was about 4 Ohm, which to me sounded somewhat reasonable, so I didn't grab deeper.
When I read, that the mosfet should be ok, I remembered, that my multimeter is a cheap one which is not capable of true rms ...
... but, I remembered, that I have a very tiny DSO.
So I powered the board by a laboratory power supply and connected one dso-channel to positive heatbed output and the other channel to the negative heatbed output channel.
I was very surprised, that the board consumed only about 90-100mA
(shown by the laboratory power supply)
This is the heatbed output in idle state:
When I turn heatbed heater on, the pwm-line turns into a straight line.
I have no idea, why the multimeter was not capable to measure any voltage.
Then I dismounted the heatbed. On Ender-3 the cable at the heatbed connector is supported by a plastic cable holder, which should prevent cable from breaking from the solder pad.
Well, the cabel was broken and in the endposition of the heatbed the broken cable touched the heater pad. That way I could measure an impedance.
After resoldering the cable I measured the impedance of the heatbed again and it showed 3 Ohm.
Not that far from previous result.
conclusion (for me): you can't even know without having checked every possible cause.
Thank you for your support!
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