<p>I'm setting up my first 3D Printer, a Prusa i3 MK2 clone. 
When I try to heat the bed, nothing happens. Then Marlin throws this error after a while:  </p>

<pre><code>Bed Heating Failed
PRINTER HALTED
Please reset
</code></pre>

<p>In Pronterface I see this in the console:</p>

<pre><code>Error:Heating failed, system stopped! Heater_ID: bed
[ERROR] Error:Heating failed, system stopped! Heater_ID: bed

Error:Printer halted. kill() called!
[ERROR] Error:Printer halted. kill() called!
</code></pre>

<p>There is 0 voltage across D8 on the Ramps board, where it is connected. When I heat up the hotend, on the other hand, which is connected to D10, I see 12V across the board's D10 terminals.</p>

<p>The bed is MK42 type.</p>

<p>My axes, extruder hotend and fans are working OK. </p>

<p>I previously burned out the 5&nbsp;V regulator on my Arduino Mega by misconnecting one of the end stops. I replaced the regulator on the board and the 5&nbsp;V supply seems to be working OK again. However I wondered if I might have damaged the board in some other respect? Or is there a config setting in Marlin I should change?</p>

[{'answer_id': 7670, 'author': 'Trish', 'author_id': 8884, 'author_profile': 'https://3dprinting.stackexchange.com/users/8884', 'pm_score': 0, 'selected': False, 'text': '<h1>Software</h1>\n<p>You might want to look at your firmware. When running a PID tune, the firmware decides on a smoothing.</p>\n<p>in Marlin, <code>configuration.h</code> contains a line that determines how much the machine shall try to work out the curves. For my ender 3 it reads:</p>\n<pre><code>#define PID_K1 0.95      // Smoothing factor within the PID\n</code></pre>\n<p>Playing with the value carefully might result in better calibration.</p>\n<h1>Hardware</h1>\n<p>A different trick to <em>widen</em> the waves might come from adjusting the physical properties of the printer:</p>\n<ul>\n<li>Make sure that no draft from the cool end fans runs over the heater block. If it does, a shroud or a little tinfoil can help to dampen the changes.</li>\n<li>e3D uses a silicon sock to isolate their heater blocks and prevent air drafting over them.</li>\n</ul>\n'}, {'answer_id': 7673, 'author': '0scar', 'author_id': 5740, 'author_profile': 'https://3dprinting.stackexchange.com/users/5740', 'pm_score': 2, 'selected': True, 'text': '<p>If you are sure that PID is enabled (and not using bang-bang heating, as this gives a very similar heating profile) and did not fix the fluctuations, the best guess for this phenomenon is that the printer board has incorrect capacitors installed on the printer board. This is not very uncommon and can be found on the internet. You should at least show the graph to the vendor and ask for support.</p>\n\n<p>If incorrect or faulty capacitors are the cause it requires desoldering, and resoldering new ones. If this is out of your comfort zone, it is better to steer your communication with the vendor to replacing the board.</p>\n'}]
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